AUTHOR INFORMATION

Section 1 of 11

Authored by Stephen G Kaler, MD, MPH, Head, Unit On Pediatric Genetics, Laboratory of Clinical Genomics, and Clinical Director, Intramural Research Program, National Institute of Child Health & Human Development (NICHD), National Institutes of Health

Edited by Christian J Renner, MD, Consulting Staff, Department of Pediatrics, University Hospital for Children and Adolescents, Erlangen, Germany; Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine.com, Inc; Margaret McGovern, MD, PhD, Vice Chair, Professor, Department of Human Genetics, Mount Sinai School of Medicine; Daniel Rauch, MD, FAAP, Director, Pediatric Hospitalist Program, Associate Professor, Department of Pediatrics, New York University School of Medicine; and Bruce A Buehler, MD, Professor, Department of Pathology and Microbiology, Chairman, Department of Pediatrics, Director, Hattie B Munroe Center for Human Genetics, University of Nebraska Medical Center

Author's Email:	Stephen G Kaler, MD, MPH
Editor's Email:	Christian J Renner, MD

eMedicine Journal, June 8 2006, VOLUME 7, Number 6

INTRODUCTION

Section 2 of 11

Background: In the nearly 45 years since the original description of Menkes kinky hair disease (MKHD), advances in understanding the clinical, biochemical, and molecular aspects of this rare disorder of copper metabolism have outstripped progress in the design of effective therapies. The most promising therapy to date, very early subcutaneous copper injections, has normalized neurodevelopmental outcome in some individuals with MKHD (approximately 30% in the author’s experience) and mitigated the neurologic effects in others. However, some patients with MKHD (nearly 50% in the author’s experience) have not derived substantive benefit from this approach, despite very early institution of treatment.

Identification of the Menkes gene by positional cloning has enabled molecular diagnosis of females who carry the gene and at-risk fetuses in certain families, enhancing preventive efforts. Evidence that the gene encodes a highly conserved copper-transporting adenosine triphosphatase (ATPase) has stimulated investigation of the molecule's normal function in prokaryotic and eukaryotic systems. Knowledge gleaned from such efforts ultimately may suggest the novel therapeutic strategies needed to achieve normal neurologic outcomes in patients with MKHD regardless of mutation severity. While early recognition of infants with MKHD prior to neurologic damage remains a fundamental requirement, the recent advances provide a glimmer of hope in efforts to improve matters for individuals with MKHD and the families who care for them.

History of the disorder

History of this disorder can be traced to as early as 1937, when Australian veterinary scientists recognized the critical role of copper in mammalian neurodevelopment through the association of copper deficiency with demyelinating disease in ataxic lambs. These animals' mothers had grazed in copper-deficient pastures throughout their pregnancies, and their offspring consequently demonstrated symmetric cerebral demyelination and gross pathologic changes, such as porencephalic cyst formation and cavitation.

Based on this connection between copper deficiency and demyelinating disease, neurologists at Oxford in 1948 investigated copper metabolism in a group of patients with multiple sclerosis (MS), a demyelinating disease of adults. Those studies excluded defective copper metabolism as the cause of MS, and Professor David Danks later identified MKHD as a human example of abnormal myelination due to copper deficiency.

Danks' discovery in 1972 was based on his recognition that the unusual hair of infants with MKHD appeared similar in texture to the brittle wool of sheep raised on copper-deficient soil in Australia, where wool production remained a major industry. He measured serum copper in 7 patients with MKHD and found low levels in all 7 individuals. Serum levels of ceruloplasmin, an important copper enzyme, were also subnormal. Thus, observations made 35 years apart concerning the effects of copper deficiency in Australian sheep became extremely relevant to a human inborn error of metabolism.

This important biochemical finding sparked renewed interest in the phenotype that had been delineated meticulously 10 years earlier by John Menkes, MD, and colleagues at Columbia University in New York. Menkes had reported 5 male infants in a family of English-Irish heritage who were affected with a distinctive syndrome of neurologic degeneration, peculiar hair, and failure to thrive. The boys appeared healthy at birth and throughout the first several months of life, but then they experienced seizures and developmental regression and ultimately died when aged 7 months to 3.5 years. The pedigree of the family strongly suggested that the condition was an X-linked genetic disease. Subsequent case reports confirmed that Menkes "kinky hair" disease was a newly recognized syndrome with unique clinicopathologic features.

The association of this disorder with abnormal copper metabolism had a number of important effects. Clinical diagnosis was facilitated by the availability of a reliable biochemical marker (ie, low serum copper and ceruloplasmin). Treatment for a previously fatal disease could be considered by way of copper replacement, and physiologically suitable forms had been reported. Delineation of the basic defect appeared possible, particularly when an excellent mouse model for the human phenotype was recognized and when cultured cells of patients with MKHD were demonstrated to have distinctive abnormalities in copper handling. The latter findings were applied rapidly as a method of prenatal detection by analysis of cultured amniocytes.

During the following 15 years, additional descriptions of clinical, biochemical, and pathologic features of patients with MKHD brought attention to the phenotypic spectrum of the disorder. Reports of treatment with copper supplementation in the classic severe type generally indicated little impact on the dismal natural history. A mild form of the disease was noted in which neurologic abnormalities were far less profound. Recognition of a close biochemical relationship between MKHD and type IX Ehlers-Danlos syndrome (ie, occipital horn syndrome [OHS]) suggested a gene locus comparable to that in the mouse, wherein similar differences in neurologic effects, connective tissue manifestations, and longevity had been reported between 2 apparently allelic variants.

Mapping studies localized the gene to the long arm of the X chromosome close to the centromere. Metallothionein, a copper protein overexpressed in Menkes cultured cells and suspected by some as the primary abnormality, was excluded from direct consideration by localization to chromosome 16 in somatic cell hybrid studies. Experience with prenatal detection increased, and biochemical tests that used chorionic villus samples were developed to enable earlier diagnosis in at-risk pregnancies. A Menkes parents-professionals association was formed in the United States.

In 1987, a female with classic MKHD caused by an X-autosome chromosomal translocation was reported. This critical observation narrowed the cytogenetic region containing the Menkes locus to Xq13, and cell lines established from this patient ultimately led to cloning of the gene. From a medical perspective, improved outcomes in several patients treated from a very early age with a copper-histidine complex were reported, and a protocol at the National Institutes of Health (NIH) was established to further evaluate the clinical and biochemical effects of this agent in patients with MKHD.

Identification of the Menkes gene by positional cloning was reported in 1993. This landmark discovery disclosed that the Menkes gene product is a member of a highly conserved family of cation-transporting ATPases, which are molecules that function in the transport of ions across cellular and intracellular membranes. In conjunction with previous data characterizing the biochemical abnormalities in patients with MKHD and their cultured cells, this finding suggests that the basic defect in MKHD is the failure of a plasma membrane pump that normally extrudes copper from cells or failure of a pump that normally transports copper into an intracellular organelle such as endoplasmic reticulum.

Thus, in the nearly 40 years since its initial description, MKHD has been the subject of extensive clinical and scientific scrutiny. The attention culminated in the detection of the faulty gene product, a discovery that provided basic insight into mammalian copper metabolism and presaged a new era in the investigation and history of this disorder.

Animal models of kinky hair disease

The mottled mouse provides an excellent animal model for MKHD. The mottled and Menkes loci are located in homologous regions of their respective X chromosomes, and several allelic variants have been recognized in the mouse, predicting the possibility of a similar situation in humans.

One of the best studied mottled mutants, the brindled (Mobr) male hemizygote, exhibits decreased coat pigmentation, tremor, general inactivity, death when aged 14 days, increased intestinal copper levels with low levels in the liver and brain, and decreased copper enzyme activities. Of great interest is the observation that healthy viability can be restored in these mutants if a single copper injection is provided during the first week of life, while treatment is ineffective when administered later (eg, when aged 12 d).

This response is also characteristic of the macular mouse, a biochemically similar model of MKHD discovered in Japan. These findings suggest the following: (1) the existence of a critical period in murine neurodevelopment during which copper is essential, and (2) the brindled mutation does not completely impede proper utilization of copper when the block in intestinal absorption is bypassed.

Male mice hemizygous for other mottled alleles (eg, tortoise, dappled, viable-brindled) also exhibit reduced viability. In contrast, the blotchy mutant (Mo-blo) has healthy viability but more pronounced connective tissue abnormalities. Cultured fibroblasts from all the mutants tested demonstrate the abnormal copper accumulation characteristic of MKHD.

Biochemical investigation of brindled and blotchy mutants has been extensive. These findings suggest that cytochrome c oxidase (CCO) may be affected more than other copper enzymes in the brindled mutant and that partial restoration of CCO activity in the brain may be responsible for the clinical improvement associated with early copper therapy.

In untreated brindled mice, CCO deficiency has been correlated with progressive neuropathologic changes. In the blotchy mutant, CCO deficiency is less severe than in the brindled mutant, whereas lysyl oxidase (LO) deficiency appears more pronounced, suggesting that the blotchy mutant may be analogous to the human occipital horn phenotype in which connective tissue manifestations predominate. Interestingly, LO response to copper treatment seems better in the brindled mutant than in the blotchy mutant. Also noteworthy is the apparent preservation of normal CCO and superoxide dismutase (SOD) activity in certain organs of both mutants, including the kidney, which is one organ that manifests the copper accumulation phenotype.

Direct measurement of dopamine beta-hydroxylase (DBH) activity in the mottled mutants is complicated by the fact that most assays for DBH require the addition of exogenous copper to samples being measured. The provision of copper presumably circumvents the basis for deficient DBH activity in vivo in tissues of these mutants. Brindled and blotchy mice in which low levels of norepinephrine (NE) in the brain indicated significant DBH deficiency actually demonstrated increased brain DBH when assayed in vitro. These findings suggested that DBH apoenzyme was available in adequate amounts, indeed amounts are perhaps increased in a compensatory manner, but that enzyme function was impaired because of unavailability of copper as a cofactor in vivo. Data on DBH response to copper therapy in the mottled mutants are limited.

Copper/zinc (Cu/Zn) SOD activity is not reduced in either mouse mutant to the same extent as the other copper enzymes studied, nor is its activity enhanced as much (if at all) by copper treatment. In one study of cultured blotchy fibroblasts, measurable SOD activity did not differ from controls. The consistent favorable clinical response to copper treatment in the brindled mutant represents a distinct difference from the experience in most patients with MKHD.

Cloning of the mottled gene by 2 laboratories (Gitscher, Mercer) and identification of the mutants (ie, brindled, blotchy, dappled) and other alleles by several laboratories (ie, Gitscher, Mercer, Boyd) have improved the understanding of the relationship between mottled phenotype and genotype. Some of these mutant alleles may hold promise for evaluating potential new therapies for MKHD.

Pathophysiology: As an X-linked disease, MKHD typically occurs in males who present when aged 2-3 months with loss of previously obtained developmental milestones and the onset of hypotonia, seizures, and failure to thrive. Characteristic physical changes of the hair and facies, in conjunction with typical neurologic findings, often suggest the diagnosis. In 1988, Baerlocher and Nadal compiled the presenting signs and symptoms of 127 patients with MKHD whose cases had been reported in the medical literature up to 1985. The less distinctive appearance of very young infants with MKHD before the onset of neurodegeneration is discussed separately below. In the natural history of classic MKHD, death usually occurs by the time the individual with MKHD is aged 3 years.

Physical presentation

The scalp hair of infants with classic MKHD is short, sparse, coarse, and twisted. The hair is often less abundant and even shorter on the sides and the back of the head than on the top. The twisted strands may be reminiscent of those in steel wool cleaning pads. The eyebrows usually share the unusual appearance. Light microscopy of patient hair illustrates pathognomonic pili torti (ie, 180° twisting of the hair shaft) and often other abnormalities, including trichoclasis (ie, transverse fracture of hair shaft) and trichoptilosis (ie, longitudinal splitting of shaft). Hair tends to be lightly pigmented and may demonstrate unusual colors, such as white, silver, or grey; however, in some individuals with MKHD, the hair is pigmented normally.

The face of the individual with MKHD has pronounced jowls, with sagging cheeks and ears that often appear large. The palate tends to be high-arched, and tooth eruption is delayed. Noisy sonorous breathing is often evident. While findings on auscultation of the heart and lungs are usually unremarkable, pectus excavatum (chest deformity) is a common thoracic finding. Umbilical and/or inguinal herniae may be present. The skin often appears loose and redundant, particularly at the nape of the neck and on the trunk.

Neurologically, profound truncal hypotonia with poor head control is invariably present. Appendicular tone may be increased with thumbs held in an adducted cortical posture. Deep tendon reflexes are often hyperactive. The suck and cry are usually strong. Visual fixation and tracking are commonly impaired, while hearing is normal. Developmental skills are confined to occasional smiling and babbling in most patients with MKHD. Growth failure commences shortly after the onset of neurodegeneration and is asymmetric, with linear growth relatively preserved in comparison to weight and head circumference. Clinical diagnostic tests often produce characteristic results (see Workup).

Biochemical phenotype

The biochemical phenotype in MKHD involves (1) low levels of copper in plasma, liver, and brain because of impaired intestinal absorption, (2) reduced activities of numerous copper-dependent enzymes, and (3) paradoxical accumulation of copper in certain tissues (ie, duodenum, kidney, spleen, pancreas, skeletal muscle, placenta). The copper-retention phenotype is also evident in cultured fibroblasts and lymphoblasts, in which reduced egress of radiolabeled copper is demonstrable in pulse-chase experiments. This constellation of biochemical findings denotes a primary defect affecting copper transport that begins with impaired absorption at the intestinal level and continues with failed utilization and handling of whatever copper is conveyed to other cells in the body.

Certain clinical features of MKHD can clearly be related to deficient activity of specific copper-requiring enzymes, and one can speculate on the effects that reduced activity of other copper enzymes would produce. Partial deficiency of DBH, a critical enzyme in the catecholamine biosynthetic pathway, is responsible for a distinctively abnormal plasma and cerebrospinal fluid (CSF) neurochemical pattern in patients with MKHD. In the author’s experience, the ratio of a proximal compound in the pathway, (dihydroxyphenylalanine [DOPA]), to a distal metabolite (dihydroxyphenylglycol [DHPG]) provides a better index of DBH deficiency in patients with MKHD than NE levels alone.

Plasma and especially CSF levels of NE, the direct product of DBH, are maintained relatively well in some patients with MKHD, presumably because of suitable compensatory mechanisms. Clinical features of patients with MKHD potentially attributable to DBH deficiency include temperature instability, hypoglycemia, and eyelid ptosis, which are autonomic abnormalities that may result from selective loss of sympathetic adrenergic function. Similar clinical problems have been reported in patients with Riley-Day dysautonomia, in which DBH deficiency has been documented, and/or in patients with congenital absence of DBH.

A recently reported copper-dependent enzyme, peptidylglycine alpha-amidating monooxygenase (PAM), is required for removal of the carboxy-terminal glycine residue characteristic of numerous neuroendocrine peptide precursors (eg, gastrin, cholecystokinin, vasoactive intestinal peptide, corticotropin-releasing hormone, thyrotropin-releasing hormone, calcitonin, vasopressin). Failure to amidate these precursors can result in 100- to 1000-fold diminution of bioactivity compared to the mature amidated forms. While deficiency of tyrosinase, a copper enzyme needed for melanin biosynthesis, is considered responsible for reduced hair and skin pigmentation in patients with MKHD, PAM deficiency may also contribute to this feature through reduced bioactivity of melanocyte-stimulating hormone, an alpha-amidated compound. PAM deficiency may have more important and wide-ranging physiologic effects that contribute to the Menkes phenotype.

Deficient CCO activity is probably a major factor in the neuropathology of MKHD. Effects on the brain are quite similar to those in individuals with Leigh disease (ie, subacute necrotizing encephalomyelopathy), in whom CCO deficiency is caused by complex IV respiratory chain defects. As in Leigh disease, patients with MKHD do not have the severe lactic acidemia associated with other complex IV defects. CCO deficiency peripherally probably also contributes to the hypotonia and muscle weakness evident in patients with MKHD.

Reduced activity of LO, another copper enzyme, also has major clinical consequences in MKHD. This enzyme normally acts to deaminate lysine and hydroxylysine as the first step in collagen cross-link formation. Decreased LO activity significantly reduces the strength of connective tissue investing numerous organs and tissues. In patients with MKHD, vascular tortuosity, bladder diverticula, and gastric polyps are all believed to result from LO deficiency.

Deficiency of Cu/Zn SOD in MKHD may lower protection against oxygen free radicals and theoretically have cytotoxic effects. Localized brain damage due to such oxidant stress has been postulated as the pathogenetic basis of Parkinson disease. Mutations in the Cu/Zn SOD gene on chromosome 21 have been associated with amyotrophic lateral sclerosis, a motor neuron disease of adult onset. The relative contribution of partial SOD deficiency to the neurodegenerative changes in patients with MKHD is difficult to assign.

Further pathology

Interesting and varied ocular pathology has been reported, including retinal hypopigmentation and vessel tortuosity, macular dystrophy, congenital cataracts, partial optic nerve atrophy and decreased retinal ganglion cells, and microcysts in the pigment epithelium of the iris.

On occasion, thymic atrophy and impaired T-cell function has been demonstrated in patients with MKHD and warrants investigation in a larger group, given the apparent predisposition to infectious illness in some patients with the syndrome. Decreased T-cell function has been reported in the macular mouse, an animal model of Menkes disease.

Frequency:

• In the US: MKHD is a relatively rare condition with incidence estimates ranging from 1 case per 100,000 live births to 1 case in 250,000. Based on the recent number of annual births in the United States (approximately 3.9 million), an estimated 16-40 infants with MKHD are expected to be born in this country each year. One third of these infants are predicted to be nonfamilial, representing new mutations.

• Internationally: Mutations in the Menkes gene occur in all racial and ethnic groups, presumably at the same frequency as occurs in the United States. Therefore, based on recent estimates of annual world births (approximately 135 million per year), an estimated 540-1350 infants with MKHD are expected to be born each year worldwide.

Mortality/Morbidity: No reliable way to predict the life span of children with MKHD exists, although most of these children die by the time they are aged 3 years. Pneumonia, leading to respiratory failure, is a common cause of death, although some patients with MKHD die suddenly in the absence of any apparent acute medical process. The major morbidity associated with MKHD involves the neurologic, gastrointestinal, and connective tissue (including vasculature) systems, as reviewed (see Pathophysiology).

Race: No particular racial or ethnic predilection for MKHD exists. For X-linked recessive lethal traits, such as in individuals with MKHD, genetic theory suggests that one third of infants with MKHD represent new mutations. Such de novo mutations are expected to occur at equal frequency among all Homo sapiens racial and ethnic groups.

Sex: MKHD affects males nearly exclusively because it is an X-linked recessive trait. Female carriers generally do not manifest symptoms unless unusual genetic circumstances are present. These include unfavorable lyonization due to skewed X-inactivation, balanced chromosomal translocations with breakpoints lying within the Menkes gene, or sex chromosome aneuploidy (ie, Turner syndrome ([45, XO karyotype]) with a Menkes gene mutation on the sole X chromosome).

Age: As noted above, individuals with MKHD typically present when aged 6-8 weeks, with parents noticing a delay in developmental progress or the appearance of unusual eye or extremity movements suggestive of seizure activity.

CLINICAL

Section 3 of 11

History: The typical history of a patient with Menkes kinky hair disease (MKHD) includes healthy pregnancy and delivery. Birth frequently occurs several weeks in advance of the estimated date of confinement or due date.

• Classic MKHD often escapes attention in the neonatal period because of its very subtle manifestations in neonates. However, several nonspecific physical and metabolic findings are commonly cited when birth histories of these babies are reviewed.


• • These findings include premature labor and delivery, large cephalohematomas in individuals born by abdominal delivery, hypothermia that necessitates warming lights or an isolette, hypoglycemia for which early feeding or support with intravenous (IV) glucose is instituted, and jaundice that requires several days of phototherapy.
  
  
  
  • Pectus excavatum and inguinal or umbilical herniae are found at birth in some patients with MKHD.
  
  
  
  • Occasionally, unusual hair pigmentation may suggest the diagnosis in newborns. However, the appearance of the hair is often unremarkable. As in healthy babies, newborns with MKHD may exhibit no hair or have normally pigmented hair. The pili torti found on microscopic examination of hair from older patients with MKHD is not usually evident in the hair of newborns with MKHD.
  
  
  
• Neurologically, newborns with MKHD generally appear to be healthy. Excessive jitteriness was noted in one patient at age 1 week.



• Transient neonatal hypothermia and hypoglycemia are not uncommon; however, infants with MKHD appear essentially healthy at birth and for the first 4-6 weeks of life.



• When the infant is aged approximately 2-2.5 months, the parents usually first suspect that something is wrong and voice their concerns to the healthcare provider.



• A steady downward spiral continues clinically, with development of progressive hypotonia, seizures, failure to thrive, and appearance of the characteristic coarse wiry hair by the time the individual with MKHD is aged 4-5 months.

Physical: As noted previously, major clinical manifestations of persons with MKHD include loss of early developmental milestones, truncal hypotonia, seizures, poor weight gain, abnormal hair, loose skin, pectus excavatum, and urinary bladder diverticula.

A considerable spectrum of severity exists in patients with MKHD and certain disorders; although once considered distinct genetic entities, they most likely represent allelic variants.

• Patients with the classic phenotype may differ in certain respects (eg, presence of functional vision, level of infant personal-social development, severity of seizures), but they invariably demonstrate profound hypotonia and motor impairment. In contrast, patients with variants of the classic phenotype demonstrate less severe overall developmental outcomes.


• • One such child evaluated at the NIH was aged approximately 7 months when developmental delay was first noted.
    • When aged 9 months, the child required surgery for bladder outlet obstruction due to massive diverticula.

    • He was diagnosed with MKHD when aged 22 months.

    • When aged 27 months, he was able to sit alone, crawl, play with toys, indicate his needs, and voice approximately 20 words with poor articulation. He was ataxic with head bobbing and tremor, and his brain MRI exhibited mild cerebellar hypoplasia. He had normal findings on EEG and no clinical seizures. His growth exhibited height between the 25th and 50th percentile for age, with weight and head circumference both slightly below the fifth percentile. His biochemical parameters (eg, plasma copper, plasma catecholamines, copper accumulation in cultured fibroblasts) did not differ significantly from values in infants with classic MKHD.

    • Apart from his asymmetric growth retardation and history of bladder diverticula, this patient resembles a reported example of mild MKHD.
  
  
  
  • Another atypical patient has been reported in whom motor development was relatively better, ataxia less severe, and connective tissue problems more prominent than the initially reported mild patient.

  • Because the neurologic impairment is less profound, other patients with conditions such as these seem unlikely to be suspected of having a condition related to MKHD. Of note, both of the patients reported above had pili torti, which aided in establishing their diagnosis.
  
  
  
• Another probable Menkes variant is type IX Ehlers-Danlos syndrome, otherwise known as X-linked cutis laxa or OHS, in reference to the pathognomonic wedge-shaped calcification that forms within the trapezius and sternocleidomastoid muscles at their attachment to the occipital bone in affected individuals.


• • This protuberance can be palpated in some patients and is demonstrable radiographically on Towne view or on appropriate sagittal CT scanning or MRI cuts. Radiologic abnormalities of the clavicles and long bones have also been noted.
  
  
  
  • Clinical findings include lax skin and joints, bladder diverticula, inguinal herniae, vascular tortuosity, and normal or slightly subnormal intelligence.
  
  
  
  • Biochemically, plasma copper and ceruloplasmin levels are in the low reference range, copper egress in cultured fibroblasts is impaired to the same degree as in classic MKHD, and activity of fibroblast LO is reduced markedly.
  
  
  
  • Additionally, some patients have signs of autonomic dysfunction (eg, syncope, episodic diarrhea) suggestive of DBH deficiency. Neurologic findings are otherwise essentially normal.
  
  
  
• Other clinical variants have been reported that involve features of both the classic Menkes and the occipital horn phenotypes.


• • One kindred study included 4 males aged 15 months to 35 years who had low or low-normal plasma copper; abnormal plasma catecholamines; and a syndrome of mental retardation, childhood-onset seizures (aged 3-8 y), neuromuscular weakness, joint abnormalities, and bladder diverticula.
  
  
  
  • Occipital exostoses were detected in the 15-year-old patient during radiologic studies performed after a sudden cerebral hemorrhage.
  
  
  
  • The 35-year-old man developed seizures when aged 3-4 years and required vesicostomy when aged 9 years for bladder outflow problems caused by diverticula. He learned to walk with the aid of crutches. His elbows became dislocated. He had the estimated intellectual capacity of an individual aged 8 years, and his speech was extremely inarticulate. His size was that of a small adult.
  
  
  
  • The members of this family who were affected with MKHD were found to have splice site mutations in the 3' region of the Menkes/OHS gene that impaired but did not eliminate proper RNA splicing; a similar type of splicing mutation was found in an unrelated patient with typical OHS.
  
  
  
  • In 1994, Kaler et al quantitated the amount of proper splicing in cultured cells associated with these mutations at approximately 20-30% of normal.
  
  
  

Causes: Mutations in the Menkes/OHS gene underlie both classic and milder phenotypes. The severity of mutations and amount of possible residual copper ATPase activity appear to be relevant to the variable clinical outcomes. Secondary deficiencies of copper-dependent enzymes are believed to cause certain of the clinical manifestations, as reviewed earlier (see Pathophysiology).

• Menkes/OHS gene: Location of the Menkes/OHS gene on the X chromosome was indicated by pedigree analysis from the time of its earliest descriptions.


• • Progressively refined localization to Xq13 was enabled by linkage studies and characterization of X chromosomal rearrangements in 2 unrelated patients.
  
  
  
  • Genomic DNA from the chromosomal breakpoint region was used to identify portions of the Menkes locus by screening complementary DNA (cDNA) libraries or by exon trapping.
  
  
  
  • The candidate gene thus identified was found to be expressed abnormally in more than 70% of patients with MKHD who were studied, and gene deletions were detectable by Southern blotting in more than 15% of these patients.
  
  
  
  • The Menkes/OHS gene is expressed in all human tissues tested, with the liver being a prominent exception. The messenger RNA (mRNA) transcript is approximately 8.5 kilobases (kb), with a long 3' noncoding portion and a coding sequence of 4.5 kb.
  
  
  
  • The predicted gene product is a 1500–amino acid molecule that is similar to numerous ion-motive ATPase molecules, including a pair of copper-transporting ATPases (copA and copB) in the bacterium Enterococcus hirae, an intracellular copper transporter (CCC2) in Saccharomyces cerevisiae, and the Wilson disease gene product.
  
  
  
• Menkes/OHS copper ATPase: A wide array of ion-motive ATPases has been characterized, and they are divided into 3 classes (ie, P, V, F).


• • The P-type ATPases, of which the Menkes gene product is an example, are so named because they form a covalently phosphorylated intermediate from transfer of the gamma-phosphate of ATP to a specific aspartate residue at the catalytic site of the protein.
  
  
  
  • V-type ATPases are those associated with vacuolar organelles (eg, lysosomes, endosomes, storage granules, Golgi vesicles).
  
  
  
  • The F-type ATPases are found in most bacteria and are associated with mitochondria in higher organisms.
  
  
  
  • The overall sequence similarity among prokaryotic and eukaryotic cation-transporting ATPases suggests that these proteins have been modified throughout evolution in response to the need for import and export of various cations across different cellular membranes.
  
  
  
  • P-type ATPases function in the regulation of intracellular ion concentrations. Those imbedded in plasma membranes function to extrude their respective ions from the cell. Other P-type ATPases are localized to the membranes of intracellular organelles (eg, sarcoplasmic reticulum, endoplasmic reticulum) and act to sequester ions within their lumens. Interaction with ATP at a specific site is believed to induce multiple conformational adjustments that reorient the molecule with respect to the membrane, creating channels for cation translocation from high-affinity binding sites on one membrane side to low-affinity binding domains oriented toward the other side. Alternative splicing that generates multiple isoforms with potential functional differences has been demonstrated for certain ATPases of this class.
  
  
  
• Menkes gene product: In the Menkes gene product, the N-terminal portion has a distinctive recurring amino acid pattern, cysteine-X-serine-cysteine, which is comparable to putative metal binding sites in the bacterial ATPases involved in transport of copper, cadmium, and mercury, respectively. Hydrophobicity analysis indicates 6-8 transmembrane domains, and the predicted protein demonstrates all the other functional domains expected of P-type ATPases. The expression of the Menkes gene in nearly all human tissues, the severe consequences of impaired function (ie, MKHD) and the high degree of evolutionary conservation all indicate the fundamental importance of the copper transport process that this gene encodes.


• • With the discovery of the Menkes gene, investigating the basic cell biological defect in greater depth became possible. Elegant studies in several laboratories (ie, Camakaris, Francis, Gitlin, Glover, Mercer) localized the Menkes/OHS gene product to the trans-Golgi apparatus, where it is involved in the delivery of copper to copper-dependent enzymes processed in the secretory pathway of cells. In addition, the Menkes/OHS ATPase appears to relocate in response to increased copper exposure, moving to the plasma membrane of cells where it presumably functions as a pump directly mediating copper exodus from cells.
  
  
  
  • This model of the gene product's locations (trans-Golgi and plasma membrane) is consistent with the copper retention phenotype of cultured Menkes cells and with induction of metallothionein (MT) in these cells at much lower experimental copper exposures than in healthy cells.
    • MT, a cysteine-rich heavy metal–binding protein, may represent a secondary line of defense against the toxicity of high intracellular copper that is required sooner than usual in Menkes cells because of a defect in the primary regulatory mechanism (ie, removal of copper).

    • The efficiency with which MT performs its detoxifying role and the extremely avid binding of MT to copper restricts the availability of the metal to cytosolic copper enzymes (eg, Cu/Zn SOD), as well as those synthesized or located in cellular compartments. Under normal conditions, MT presumably helps maintain low intracellular levels of free copper while permitting activation of the copper enzymes. However, in MKHD, chronic MT induction due to failure of normal copper transport disrupts this balance.

    • Failure to extrude copper from intestinal mucosal cells into the blood explains the accumulation of copper in these cells and the consequent reduced delivery of copper to the liver in individuals with MKHD. Similarly, failed copper export by placental cells accounts for the placental copper accumulation observed in pregnancies affected by MKHD and the low hepatic copper levels in fetuses with MKHD. Failure of copper export by vascular endothelial and glial cells comprising the blood-brain barrier explains low copper levels and reduced copper enzyme activities in the brain. Because the Menkes gene is weakly expressed in the liver, this organ must possess alternative mechanisms for copper excretion (ie, Wilson copper ATPase) and thus does not manifest the copper accumulation, MT induction, or copper enzyme deficiencies found in other tissues.
  
  
  
• Mutational analysis of the Menkes/OHS gene: Identification of the Menkes/OHS gene provided the opportunity for molecular analysis of patients with MKHD. Before the genomic organization of the gene was characterized completely, the reverse transcription–polymerase chain reaction method (RT-PCR) offered a particularly useful approach to mutation analysis.


• • RT-PCR involves isolation of intact RNA from cultured fibroblasts or lymphoblasts and reverse transcription of the 8.5-kb Menkes message using oligodeoxythymidine as a primer. This reaction generates a full-length cDNA that is suitable as a template for PCR using gene-specific primers. The entire cDNA from patients with MKHD thus may be obtained for direct sequence analysis.
  
  
  
  • Menkes/OHS gene mutation analysis by this method, and more recently from genomic DNA directly, has been conducted in several laboratories (ie, Horn, Kaler, Mercer, Ogawa), contributing important information about the molecular correlates of certain clinical and biochemical phenotypes and about functional aspects of this copper-ATPase. Molecular diagnosis also provides practical benefit to Menkes families with regard to detection of fetuses with MKHD and females who are carriers.
    
  
  
  

WORKUP

Section 4 of 11

Lab Studies:

• In addition to the subtle clinical manifestations in neonates with Menkes kinky hair disease (MKHD), early diagnosis is complicated by the unreliability of the usual biochemical markers (ie, low serum copper and ceruloplasmin) during the first several weeks of life.



• Laboratory findings in MKHD include low copper and ceruloplasmin, although values for these are also low in healthy infants during the first 6 weeks of life and thus are not diagnostic for MKHD during this time frame. The levels in healthy newborns overlap those of patients with MKHD.



• In contrast, plasma and CSF catechol levels are distinctively abnormal in patients with MKHD at all ages, including the newborn period and even prenatally. As noted in Pathophysiology, high levels of the catechols DOPA, dihydrophenylacetic acid, and dopamine and low level of DHPG, the deaminated metabolite of NE, are hallmarks of the partial DBH deficiency invariably associated with MKHD and OHS. This rapid and reliable plasma or CSF catechol assay is available on a research basis at NIH.



• Copper egress in cultured fibroblasts is a time-honored method for diagnosis of MKHD and OHS. Considered a definitive diagnostic test, it requires propagation of cells obtained from a skin biopsy for at least several weeks before the assay can be performed. The assay is being replaced by molecular analysis but remains useful for laboratories with experience in working with radiolabeled copper (half-life of copper Cu-64 is approximately 12 h) and in the conduct of pulse/chase experiments.



• Because optimal success of any therapeutic strategy for this condition requires recognition of patients with MKHD before the onset of neurologic symptoms, rapid tests that can reliably diagnose or exclude MKHD during the neonatal period are useful.


• • One such test recently recognized is plasma catecholamine analysis (see Other Tests). Plasma catechol levels distinctively outside the reference range, indicating deficiency of DBH, have been demonstrated in a fetus as well as newborns with MKHD. Sufficient data have now accrued that this assay is considered a valuable tool for rapid accurate diagnosis of MKHD in the early neonatal period when interpretation of other biochemical tests is difficult.
  
  
  
  • The placental copper level, which is increased in MKHD, represents another reliable biochemical marker for neonatal diagnosis. Rapid molecular diagnostic assays eventually may facilitate early diagnosis. Realistic consideration of newborn screening for MKHD requires more predictably effective therapies than are currently available but seems theoretically possible.
  
  
  
• Expression of MKHD in females: Several female patients with MKHD have been reported in whom chromosome rearrangement, XO/XX mosaicism, or unfavorable lyonization was responsible for expression of the full phenotype. With respect to detection of females who are carriers, clinical and biochemical parameters have not been uniformly reliable.


• • Serum copper and ceruloplasmin levels are within the reference range in carriers, as are plasma catecholamine levels (unpublished observations).
  
  
  
  • Copper egress in cultured cells of some obligate carriers demonstrate values within the range of males with MKHD or intermediate between normal and affected, but many have values that overlap with the reference range, presumably because of lyonization and apparent selection against the mutant cell type.
  
  
  
  • Pili torti in the hair of the mother of a patient with MKHD is considered definitive proof of her status as a gene carrier (see Other Tests).
  
  
  
  • As in prenatal testing, molecular diagnostic approaches aid immensely in carrier detection once a given family's mutation has been characterized in a male with MKHD.
  
  
  

Imaging Studies:

• The following imaging studies are often helpful in the evaluation and treatment of patients with MKHD or OHS:


• • Brain MRI to assess for gross structural lesions, degree of myelination, and vascular tortuosity
    • White matter abnormalities reflecting impaired myelination, diffuse atrophy, ventriculomegaly, and tortuosity of cerebral blood vessels are typical findings on brain MRI.

    • Subdural hematomas are common in infants with MKHD, and stroke can occur in patients with the disease who survive longer.
  
  
  
  • Magnetic resonance angiography (MRA) of the brain for closer detail of vasculopathy: The "corkscrew" appearance of cerebral vessels is well visualized by MRA, a noninvasive method for study of the vasculature.
  
  
  
  • Echocardiography: Dysplastic coronary vessels may be detectable by echocardiography.
  
  
  
  • Cystography or pelvic ultrasonography: These studies reveal diverticula of the urinary bladder in nearly every patient with MKHD.
  
  
  
  • Abdominal ultrasonography: This study is used to assess for antral polyps (a rare clinical problem in MKHD).
  
  
  
  • Radiography: These images often disclose abnormalities of bone formation in the skull (wormian bones), long bones (metaphyseal spurring), and ribs (anterior flaring, multiple fractures).

  
  
  

Other Tests:

• Placental copper level: In pregnancies at risk for MKHD, determination of the placental copper level is a reliable and fairly rapid diagnostic test in the newborn period. According to J. Centano of the US Armed Forces Institute of Pathology (personal communication), placental copper is 3- to 5-fold elevated in pregnancies affected by MKHD relative to healthy controls.



• Pili torti on light microscopic examination of hair


• • Pili torti on light microscopic examination of hair is another reliable diagnostic test. However, as with plasma copper and ceruloplasmin, this sign is not useful for very early diagnosis (ie, prior to neurologic symptoms) because the hair in individuals with MKHD is often normal from birth until several months of age.
  
  
  
  • Pili torti in the hair of the mother of a patient with MKHD is considered definitive proof of her status as a gene carrier. However, this hair abnormality is detectable in only approximately one half of obligate Menkes heterozygotes. Thus, even if microscopic examination of hair from a potential female heterozygote is negative for pili torti, the carrier state cannot be ruled out.
  
  
  
• Molecular analysis: Molecular analysis of the Menkes/OHS gene has been approached in several ways. The author favors a multiplex PCR assay to screen for deletions, followed by heteroduplex analysis (either D-HPLC or manual) with DNA sequencing used to confirm abnormalities. The author sequences the entire coding region and intron-exon junctions if screening approaches do not suggest the location of mutation within 1 of the 23 exons that comprise the coding sequence of the gene. To date, the author has found mutations in more than 94% of NIH-protocol patients.



• Electroencephalograms: EEGs are used routinely to investigate possible seizure activity. EEG findings are usually moderately to severely abnormal, although normal tracings have been recorded in some individuals with classic MKHD.

Procedures:

• Lumbar puncture (ie, spinal tap) to examine the CSF is almost always performed in the early evaluation of infants manifesting neurodevelopmental symptoms.



• Skin biopsy procedure to establish fibroblast cultures as a source of patient RNA and DNA or to perform diagnostic studies (eg, copper transport assays) may be requested for infants suspected of having MKHD.

Pathologic changes of the vasculature (tortuosity and ectasia) are prominent in MKHD. Defective elastin fibers have been demonstrated within the internal elastic lamina, tunica media, and intimal layers of arteries and arterioles.

TREATMENT

Section 5 of 11

Medical Care: Three fundamental issues must be addressed in configuring therapeutic strategies for individuals with Menkes kinky hair disease (MKHD): (1) the block in intestinal absorption of copper must be bypassed, (2) copper must be made available to the enzymes within cells that require it as a cofactor, and (3) infants with MKHD must be identified and treatment commenced very early in life before irreparable neurodegeneration occurs.

• Published experience on this topic indicates that parenteral administration of copper in any form restores circulating copper and ceruloplasmin to reference range levels and that oral copper does not (except copper nitriloacetate, in some patients).
  • While low hepatic copper stores are replenished quickly by parenteral therapy, brain copper during treatment increases only gradually, if at all, consistent with trapping of copper within cells comprising the blood-brain barrier.

  • CSF fluid copper levels increased quickly in one reported patient with MKHD when fresh frozen plasma was transfused just prior to IV copper histidine; however, no apparent clinical benefit was discerned.

  • More recently, biochemical and molecular investigations of rodent neuroglial cells have confirmed the role of the MKHD homolog in delivery of copper to the brain.



• The activities of copper enzymes, which are more difficult to study in a detailed fashion in humans than in the mouse, remain subnormal. Responsiveness to copper therapy has been evaluated in various tissues for CCO, serum amine oxidase, DBH, and SOD.
  • The lack of pretreatment data for brain or muscle CCO activity precludes knowing whether copper replacement has a partial positive effect on this enzyme, the deficiency of which seems primarily responsible for neurologic damage in patients with MKHD and whose activity is increased in mouse mutants following copper treatment.

  • Serial skin biopsies are required to formally assess the effect of copper treatment on LO activity. Clinical evidence (ie, darkened hair) reflects that tyrosinase activity is increased by copper replacement in some patients.

  • Ceruloplasmin is the one copper enzyme whose activity always normalizes in response to copper therapy because this enzyme is synthesized in the liver, where the Menkes gene is not expressed at a high level.



• In patients with MKHD who are treated very early with copper injections, clinical outcomes have varied. In the author’s experience, approximately 30% of patients with classic MKHD who are identified and treated within the first 10 days of life show normal neurodevelopmental outcomes. Characterization of the specific mutations in such individuals has been helpful in suggesting that partial activity of certain mutant copper ATPases may underlie the disparate clinical outcomes observed.

• Because neurodevelopmental status in the 5-day-old brindled mice that are cured by copper injection is considered the equivalent of third-trimester human fetuses, the author attempted in utero treatment in a fetus with MKHD at 32 weeks’ gestation whose parents found termination unacceptable and who understood the associated risks.
  • Several ultrasonographically guided intramuscular injections of copper histidine raised fetal plasma copper and ceruloplasmin levels, but the distinctively abnormal plasma catechol pattern persisted.

  • After pulmonary maturity was documented, the infant was delivered at 35.5 weeks’ gestation, and daily copper injections were prescribed.

  • The treatment ultimately proved unsuccessful; failure to thrive, EEG abnormalities, and characteristic bone lesions developed. The infant died when aged 6 months because of pneumonitis.

  • This patient's mutation was later demonstrated to be a severe one, with no functional copper transport activity predicted, and quantitation of postmortem brain copper confirmed abnormally low levels in comparison to an age-matched infant control.

  • Therefore, despite normalization of circulating copper levels, delivery to the brain was impaired in the context of a severe Menkes gene mutation. The outcome in this case, and the significant fetal and maternal risks involved suggests that such intervention be viewed with considerable caution in future MKHD cases.

• In another patient with MKHD who was treated from a very early age (aged 8 d), normal neurodevelopment was achieved with very early copper treatment.
  • The family mutation in this instance was a small duplication within a splice junction that was associated with 2 mutant transcripts, 1 of which contained a small in-frame deletion that potentially encodes a functional Menkes copper ATPase.

  • Evidence for partial activity can be drawn from the patient's older brother, a neurologically impaired patient with MKHD who did not have the benefit of early therapy but in whom copper injections produced noticeable darkening of the hair, indicating activation of the copper enzyme tyrosinase (the Menkes gene product recently was demonstrated in vitro as necessary for this process).

  • The infant with MKHD who began treatment when aged 8 days exhibited healthy neurodevelopment, including independent walking, by age 14 months. Treatment was discontinued when the child was aged 4 years, with no adverse effects.

  • Currently aged nearly 13 years, the child attends public school with age-appropriate peers and reportedly exhibits no significant neurologic abnormalities.



• While copper replacement does not provide substantive neurologic improvement in all patients with MKHD who are treated very early or in older individuals with MKHD, its use has been associated with modest clinical benefit, including decreased seizure frequency and reduced irritability. No evidence that copper treatment influences life span in patients with MKHD in a consistent fashion exists. In light of the possibility of small clinical benefits or improved patient comfort in a hopeless disease, decisions concerning copper replacement treatment in symptomatic patients perhaps best are made by the parents, following frank discussion of the very limited benefits that can be expected. In instances where the diagnosis is made prior to the onset of neurologic damage, copper replacement is clearly indicated because the prospect of preventing the neurodegenerative features exists, at least for some such individuals.

• Proximal renal tubular damage is a known adverse effect of copper overload. These effects presumably relate to exacerbation of the natural tendency of the Menkes kidney to sequester copper. However, the clinical significance of this adverse effect is minor in most treated patients because renal losses rarely reach the point where replacement (eg, oral bicarbonate) is needed. Concomitant treatment with penicillamine, a copper-chelating agent, has been used in some patients with MKHD with the rationale of preventing copper overload.

• Another therapeutic agent that has received attention is vitamin C, which may limit interaction between copper and MT; its capacity as a reducing agent may enhance copper uptake by cells. While experience with such treatment is scant, apparently vitamin C does not significantly improve the biochemical or clinical problems in patients with MKHD.

• Vitamin E has also been suggested as therapy for individuals with MKHD, presumably for its antioxidant property, which may reduce the effects of Cu/Zn SOD deficiency.

• The carbamic acid derivative, diethyldithiocarbamate (DEDTC), is a chelating agent that forms lipophilic complexes with copper.
  • When fed to rats, DEDTC increases copper levels in the brain.

  • In macular mice that die by age 2 weeks without copper treatment, intraperitoneal administration of DEDTC or dimethyldithiocarbamate (DMDTC) resulted in normal survival in the absence of any copper treatment. Furthermore, survival was correlated with increases in macular brain copper levels.

  • In mice that received no exogenous copper and 200 mg/kg DMDTC, the brain copper level was the same as in healthy controls.

  • These experiments suggest that the lipophilic complex was able to bypass the block in macular brain copper uptake. Although toxicity considerations may prohibit long-term use of such agents in humans, the principle that lipid-soluble complexes can enhance copper transport across cellular membranes deserves further attention with respect to treatment of individuals with MKHD.

• Gene therapy for persons with MKHD is a theoretical possibility, although a number of potential problems would be faced.
  • Because gene therapy requires targeting of specific organs, a disease similar to MKHD, which effects nearly every cell in the body, is not amenable to full correction. Assuming the brain is the target organ, concern regarding the potential toxicity of gene therapy viral vectors is heightened.

  • The gene needs to be delivered to many cells, and expression needs to be sustained. The gene product, when produced, has to be targeted to the appropriate membrane.

  • Coproduction of native mutant forms of the copper ATPase could inhibit proper function of the normal molecule expressed by the introduced gene. Parenteral copper replacement would likely remain necessary in order to circumvent the defect in intestinal absorption.

  • Despite these significant caveats, functional characterization of the Menkes copper ATPase, progress in developing systems of gene delivery to the brain, and the severe nature of the untreated condition may render MKHD a candidate for gene therapy in the future.



• A more recent treatment consideration, intrathecal copper administration, relies on several lines of evidence for support, including (1) NIH treatment experience to date, (2) human and animal data indicating that the Menkes gene (and homolog) mediates copper delivery to the brain in mammals, and (3) the discovery of a class of intracellular copper transporters named copper chaperones that are not dependent on the Menkes transporter.
  • The copper chaperones were identified in the low eukaryote yeast Saccharomyces cerevisiae, and their human counterparts were cloned subsequently.

  • The human protein HAH1 delivers copper to the Menkes ATPase within the secretory pathway of cells; CCS1 delivers copper to Cu/Zn SOD, which is synthesized in the cytosol on free ribosomes; COX17 delivers copper to CCO, located in the mitochondria of cells.

  • If copper is injected directly into the CSF, normal uptake into neuronal cells as well as intracellular delivery to Cu/Zn SOD and CCO (via CCS1 and COX17) should occur in patients with MKHD. This treatment is not expected to correct deficiency of the secreted glycoprotein enzyme DBH in the brain because a normal Menkes gene product is needed to incorporate copper into DBH. However, indirect evidence reflects that normal DBH activity is not critical for normal neurologic functioning from individuals with congenital absence of DBH, from patients with MKHD with good neurologic outcomes following very early treatment, and from individuals with OHS.

  • Obviously, safety considerations must be addressed and clarified before intrathecal copper is actually employed in infants with MKHD; these safety considerations are being addressed and clarified via animal studies.
  
  
  
  • Whatever mode of treatment for MKHD is employed, intervention at the earliest possible moment is of paramount importance because the window of opportunity before neurologic injury is no longer than several months.

  • L-threo-dihydroxyphenylserine is used for amelioration of DBH deficiency.
    • L-threo-dihydroxyphenylserine (L-DOPS) is a synthetic amino acid converted to NE by the enzyme aromatic-L-amino acid decarboxylase. Provision of this compound to patients with MKHD should increase their levels of NE and DHPG (the deaminated metabolite of NE) because the block in DBH activity is bypassed. L-DOPS should correct the typical neurochemical abnormalities in plasma and theoretically in CSF if L-DOPS crosses the blood-brain barrier, which is not known.

    • The precise contribution of DBH deficiency to the MKHD phenotype is unclear. The autosomal recessive trait, congenital absence of DBH, is evidently not lethal in humans, as per reports of adults with MKHD in whom dysautonomic symptoms (ie, orthostatic hypotension, eyelid ptosis, chronic diarrhea) were the predominant neurologic abnormalities. However, in mice with targeted disruption of the murine DBH gene, fetal and perinatal lethality, failure to thrive, and abnormal cold acclimatization occur. Given this murine phenotype, correcting the neurochemical abnormalities in patients with MKHD may contribute to improved neurodevelopmental outcomes.

    • Similarly, in patients with OHS, treatment with L-DOPS should correct neurochemical abnormalities and resolve dysautonomic symptoms, which include orthostatic hypotension and chronic diarrhea.

    • A clinical trial at the NIH to evaluate this agent is planned.

Surgical Care: Patients with MKHD tolerate surgery well and do not appear to have a heightened anesthetic risk. Certain surgical situations commonly arise in patients with MKHD.

• Myringotomy tubes are needed for chronic otitis media.



• Gastrostomy tube placement is required for feeding problems.



• Occasionally, repair of bladder diverticula is necessary.

Consultations: Consultation with multiple specialists, ideally at a central location (eg, academic pediatric medical center), is often very helpful in the care and treatment of individuals with MKHD. The following specialties are particularly useful for the patients and their families:

• Medical geneticist (eg, for counseling and guidance on recurrence risks, prenatal assessment of subsequent pregnancies, carrier testing of at-risk family members)



• Neurologist (eg, for seizure management, developmental assessment)



• Gastroenterologist and nutritionist (for feeding issues)



• Urologist (for management of urinary tract issues, including obstruction related to bladder diverticula)



• Otolaryngologist (if chronic ear infections develop)



• Dentist (for caries prevention)

• Psychologist/social worker (if needed, to help parents and family members with emotional and practical economic concerns related to the care of an infant or child with MKHD)

• Physical and occupational therapist (to maximize neurodevelopmental outcome)

Diet: In general, maximizing caloric intake in children with MKHD is important because their weight gain and overall nutritional status is often poor. This can be accomplished by the addition of formula supplements (eg, Polycose, MCT oil) or by emphasizing high-calorie foods, such as cheese and yogurt. Often, formal evaluation by a gastroenterology/nutrition consultant, as noted above, is warranted with consideration of aggressive caloric supplementation via nasogastric or gastrostomy feeding tubes.

MEDICATION

Section 6 of 11

Drug Category: Trace metals -- IV/SC copper in a variety of formulations has been used to treat individuals with Menkes kinky hair disease (MKHD) and OHS during the past 30 years. Whether any particular preparation is superior to another in terms of neurologic outcomes is not clear; the biology of the Menkes transporter suggests that uptake of copper into cells is not dependent on the chemical form in which copper is introduced by SC injection.

Copper chloride, copper histidine, and copper sulfate have been used in humans. IP copper chloride is curative in the brindled mouse mutant. Copper chloride injections have not been reported in the very early treatment of individuals with MKHD; all experience with very early treatment has been with copper histidine. Therefore, from the evidence available, whether one copper salt conveys superior treatment efficacy is not clear. Copper chloride and copper sulfate are available commercially in the United States, whereas copper histidine is not. Anecdotal evidence reflects that copper sulfate can produce significant injection site inflammation.

Drug Name	Copper chloride (Cupric chloride, Copper trace) -- Available from Abbott Pharmaceuticals (1-800-937-6100) in a concentration of 2 mg/5 mL. Therefore, SC injection of 500 mL provides 200 mcg of copper. Proximal renal tubular damage presumably related to exacerbation of natural tendency of kidney in patients with MKHD to sequester copper; clinical significance is minor in most treated patients because renal losses rarely reach the point where replacement (eg, PO bicarbonate) is needed.
Pediatric Dose	<12 months: 0.5 mL SC bid >12 months: 0.5 mL SC qd
Contraindications	Documented hypersensitivity
Interactions	None reported
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Proximal renal tubular damage may occur; in patients with MKHD receiving exogenous copper, increased urinary copper excretion, increased fractional excretion of uric acid, aminoaciduria, renal tubular acidosis, and elevated urinary beta2-microglobulin (marker of renal tubular injury) have been noted

Drug Name	Copper histidine -- For use in NIH Protocol #90-N-0149, a freeze-dried (for enhanced stability) preparation is prepared by the NIH Pharmaceutical Development Service, using the following stepwise procedure: 1. Bubble nitrogen into water for injection for at least 20 min. 2. Weigh 1.345 g CuCl2 dihydrate and 2.45 g L-histidine in separate beakers. 3. Dissolve CuCl2 with water and do the same with L-histidine separately at room temperature; mix well. 4. Add both solutions together; blue color intensifies; mix well. 5. Adjust pH to 7.30-7.4 with 0.1 N NaOH or HCl. 6. Adjust volume to 1000 mL. 7. Filter through a Silo filter U containing a 0.22-micrometer Durapore filter using sterile technique. 8. Aliquot, gravimetrically, 2 g (2 mL) into each 5-mL sterile clear vial and place them on a tray for the freeze-dryer. 9. Freeze to -30° C and then freeze-dry until contents reach room temperature. 10. Stopper vials under vacuum, break off vacuum, and remove trays from freeze-dryer. 11. Seal vials with flip-off aluminum seals. 12. Refrigerate. The product is stable for at least 1 mo when stored as freeze-dried product at room temperature. However, patients' families typically store vials in their home freezers. For use in patients, contents of a vial are reconstituted with 2 mL NS, providing a solution of 500 mcg/mL for SC injection. Dose based on serum copper and ceruloplasmin levels and copper balance studies in treated patients. Proximal renal tubular damage presumably related to exacerbation of natural tendency of kidney in patients with MKHD to sequester copper; clinical significance is minor in most treated patients because renal losses rarely reach the point where replacement (eg, PO bicarbonate) is needed.
Pediatric Dose	<12 months: 0.5 mL SC bid >12 months: 0.5 mL SC qd
Contraindications	Documented hypersensitivity
Interactions	None reported
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Proximal renal tubular damage may occur; in patients with MKHD receiving exogenous copper, increased urinary copper excretion, increased fractional excretion of uric acid, aminoaciduria, renal tubular acidosis, and elevated urinary beta2-microglobulin (marker of renal tubular injury) have been noted

Drug Name	Cupric sulfate -- Available in Argentina from Farmacologia Argentina de Avanzada (FADA) in a concentration of 2 mg/5 mL (400 mcg/mL); has been used in MKHD there and in Spain. Proximal renal tubular damage presumably related to exacerbation of natural tendency of kidney in patients with MKHD to sequester copper; clinical significance is minor in most treated patients because renal losses rarely reach the point where replacement (eg, PO bicarbonate) is needed.
Pediatric Dose	<12 months: 0.5 mL SC bid >12 months: 0.5 mL SC qd
Contraindications	Documented hypersensitivity
Interactions	None reported
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Proximal renal tubular damage may occur; in patients with MKHD receiving exogenous copper, increased urinary copper excretion, increased fractional excretion of uric acid, aminoaciduria, renal tubular acidosis, and elevated urinary beta2-microglobulin (marker of renal tubular injury) have been noted

Drug Category: L-threo-dihydroxyphenylserine (L-DOPS) -- This agent is used to ameliorate dopamine-beta-hydroxylase (DBH) deficiency.

Drug Name	L-threo-dihydroxyphenylserine (L-DOPS) -- Synthetic amino acid converted to NE by enzyme aromatic-L-amino acid decarboxylase. Provision to patients with MKHD should increase levels of NE and DHPG (deaminated metabolite of NE) because block in DBH is bypassed. L-DOPS should correct typical neurochemical abnormalities in plasma of patients with MKHD (and theoretically in CSF, if L-DOPS crosses blood-brain barrier, which is not known).
Adult Dose	250 mg PO bid initial; can be adjusted based on levels of plasma and CSF catechols and DOPA/DHPG and DOPAC/DHPG ratios or based on presence of adverse effects Incremental dosage increases not to exceed 50%
Pediatric Dose	20 mg L-DOPS (estimated 5 mg/kg body weight) PO bid initial
Contraindications	Documented hypersensitivity
Interactions	None reported
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Adverse effects (eg, nausea, vomiting, headache, dry mouth, transaminase elevations) have been observed in fewer than 1% of adults, in whom this compound has been used extensively for a number of dysautonomia syndromes; because many of these symptoms are impossible or difficult to detect in infants, a low threshold is present for withholding this agent if any unusual symptoms (eg, excessive irritability) are associated temporally with administration

FOLLOW-UP

Section 7 of 11

Further Outpatient Care:

• Several points can be made concerning the general care of patients with Menkes kinky hair disease (MKHD) and their families.


• • Genetic counseling is a very important element. As an X-linked recessive trait, the Menkes gene is transmitted by asymptomatic females who are carriers to 50% of their male offspring (who are affected) and to 50% of their female offspring (who are gene carriers). Conversely, 50% of both male and female offspring are healthy. Thus, the overall risk of a child with MKHD for a woman who is a documented female carrier is 1 in 4 (25%) for each pregnancy (ie, 1 in 2 chance that the sex is male, multiplied times the 1 in 2 chance that the male inherits the Menkes gene). Offer counseling, carrier testing, and, if indicated, prenatal diagnosis to female relatives of a documented gene carrier.
  
  
  
  • Concerning pediatric immunizations in infants with MKHD, no specific contraindications exist, now that the pertussis component is acellular. Seasonal vaccination against influenza is recommended.
  
  
  
  • Prophylaxis against urinary tract infections (eg, Bactrim 2 mg/kg PO qd) is warranted in patients with bladder diverticula.
  
  
  
  • Physical and/or occupational therapy is useful stimulation and can maximize developmental attainment in patients with MKHD. Such therapy is tailored to the specific child based on his level of neurologic function. Aspects of physical and/or occupational therapy can also be taught to parents for application in the home.
  
  
  
  • MKHD has a substantial emotional impact on the family, and psychosocial support often can be valuable. Just as no health is as vibrant as that of a child, no sickness is as dramatic. Parents of patients with MKHD often have the pain of watching the transition from apparent good health to essentially irrevocable illness within the first several months of life. Anger, disbelief, guilt, and anxiety regarding an uncertain future are common reactions. Concerning the latter, no reliable way to predict the life span of children with MKHD exists; however, most of these children die by the time they are aged 3 years. Pneumonia leading to respiratory failure is a common cause of death, although some patients with MKHD die suddenly in the absence of any acute medical process.
  
  
  

Deterrence/Prevention:

• Genetic counseling and prenatal diagnosis (when available and desired) can be helpful in preventing MKHD. However, an estimated one third of all incidents of MKHD result from new mutations.



• Reliable prenatal diagnosis of MKHD on biochemical grounds has been offered by the John F. Kennedy Institute in Glostrup, Denmark, for nearly 25 years. This testing is indicated for pregnancies in known or suspected female carriers. Carrier status must be suspected in a woman and her female relatives (mother, sisters, daughters) following the diagnosis of MKHD in a son. Recurrence risk in future pregnancies of such women may be as high as 25%.



• Abnormal egress of radiolabeled copper in cultured amniocytes (reduced compared to normal, ie, a higher percentage of copper retained by cells) was the basis of the original prenatal testing. When techniques for obtaining fetal tissue earlier in gestation (ie, chorionic villus sampling) became available, diagnostic criteria derived from analysis of those tissues were developed (elevated copper content and abnormal copper egress in cultured chorionic cells). In using chorionic villus copper content as the marker, avoiding contamination from the instrument used to obtain the sample or from incomplete separation of the maternal decidua is necessary. The most reliable biochemical marker using chorionic villus specimens has been retention of radiolabeled copper in cultured chorionic cells after a 20-hour pulse and 24-hour chase. Knowledge of the gene for MKHD enables prenatal testing by molecular means for families in which the proband's mutation has been characterized.

MISCELLANEOUS

Section 8 of 11

Medical/Legal Pitfalls:

• No specific medicolegal pitfalls exist. Occasionally, healthcare providers are asked to write letters to ensure the delivery of appropriate developmental services for patients with Menkes kinky hair disease (MKHD).

TEST QUESTIONS

Section 9 of 11

CME Question 1: A 4-month-old male infant presents with hypotonia and loss of early developmental milestones. The infant's hair had a fine texture at birth but now appears coarse and twisted. The hepatic concentration of which of the following is expected to be abnormal?

A: Iron
B: Glycogen
C: Copper
D: Albumin
E: None of the above

The correct answer is C: Liver copper concentration is abnormally low in infants with Menkes kinky hair disease, an X-linked disorder of copper transport, because of impaired gastrointestinal absorption of copper.

CME Question 2: A healthy appearing newborn infant of African heritage exhibits unusual frosted hair coloration with dark hair strands and silver tips. Which of the following are diagnostic considerations?

A: Cystic fibrosis
B: Menkes kinky hair disease
C: Hypothyroidism
D: Oculocutaneous albinism
E: Down syndrome

The correct answer is B: Because of deficient activity of the copper-dependent enzyme tyrosinase, newborns of African heritage with mutations in the Menkes kinky hair disease copper transporter gene can have dual hair color.

Pearl Question 1 (T/F): Infants with Menkes kinky hair disease appear neurologically normal at birth.

The correct answer is True: Neurologic symptoms typically are not manifest until the infant with Menkes kinky hair disease is aged 6-10 weeks.

Pearl Question 2 (T/F): A woman with a 2-generation family history of Menkes kinky hair disease (MKHD), including her previously born son, is pregnant with a male fetus. Her recurrence risk for MKHD in this pregnancy is 67%.

The correct answer is False: With a male fetus, recurrence risk of MKHD is 50% for an obligate heterozygote such as the mother in this vignette.

Pearl Question 3 (T/F): Copper treatment in individuals with Menkes kinky hair disease can be associated with renal tubular injury.

The correct answer is True: Copper accumulates in renal tubular cells because of defective copper egress and can impair normal renal absorptive mechanisms.

Pearl Question 4 (T/F): Occipital horn syndrome is a mild form of Menkes kinky hair disease associated with mutations in the same gene.

The correct answer is True: Occipital horn syndrome is typically caused by splice junction mutations that reduce but do not eliminate proper messenger of RNA (mRNA) splicing and which presumably allow some normal copper transport to occur.

PICTURES

Section 10 of 11

Caption: Picture 1. Classic Menkes kinky hair disease in an 8-month-old male infant. Note the abnormal hair, eyelid ptosis, and jowly facial appearance.
	View Full Size Image
	eMedicine Zoom View (Interactive!)
Picture Type: Photo
Caption: Picture 2. Adolescent patient with typical occipital horn syndrome. Note elbow dislocations and genu valgum. Radiographs exhibited bilateral occipital exostoses of the skull and club-shaped distal clavicles.
	View Full Size Image
	eMedicine Zoom View (Interactive!)
Picture Type: Photo
Caption: Picture 3. Successfully treated classic Menkes kinky hair disease. Diagnosis at birth enabled copper therapy to begin when the infant was aged 8 days. The child walked independently when aged 14 months. This patient's mutation (IVS8,AS,dup5) was associated with a transcript harboring a small in-frame deletion, potentially encoding a functional copper adenosine triphosphatase (ATPase).
	View Full Size Image
	eMedicine Zoom View (Interactive!)
Picture Type: Photo
Caption: Picture 4. Menkes kinky hair disease copper adenosine triphosphatase (see text for detailed discussion).
	View Full Size Image
	eMedicine Zoom View (Interactive!)
Picture Type: Image

BIBLIOGRAPHY

Section 11 of 11

• Amaravadi R, Glerum DM, Tzagoloff A: Isolation of a cDNA encoding the human homolog of COX17, a yeast gene essential for mitochondrial copper recruitment. Hum Genet 1997 Mar; 99(3): 329-33[Medline].
• Baerlocher K, Nadal D: [Menkes syndrome]. Ergeb Inn Med Kinderheilkd 1988; 57: 77-144[Medline].
• Bennetts HW, Chapman FE: Copper deficiency in sheep in Western Australia: a preliminary account of the aetiology of enzootic ataxia of lambs and an anemia of ewes. Aust Vet J 1937; 13: 138-49.
• Camakaris J, Voskoboinik I, Mercer JF: Molecular mechanisms of copper homeostasis. Biochem Biophys Res Commun 1999 Aug 2; 261(2): 225-32[Medline].
• Chelly J, Tumer Z, Tonnesen T, et al: Isolation of a candidate gene for Menkes disease that encodes a potential heavy metal binding protein. Nat Genet 1993 Jan; 3(1): 14-9[Medline].
• Danks DM, Campbell PE, Walker-Smith J, et al: Menkes' kinky-hair syndrome. Lancet 1972 May 20; 1(7760): 1100-2[Medline].
• Danks DM, Cartwright E, Stevens BJ, Townley RR: Menkes' kinky hair disease: further definition of the defect in copper transport. Science 1973 Mar 16; 179(78): 1140-2[Medline].
• Francis MJ, Jones EE, Levy ER, et al: A Golgi localization signal identified in the Menkes recombinant protein. Hum Mol Genet 1998 Aug; 7(8): 1245-52[Medline].
• Grange DK, Kaler SG, Albers GM, et al: Severe bilateral panlobular emphysema and pulmonary arterial hypoplasia: unusual manifestations of Menkes disease. Am J Med Genet A 2005 Dec 1; 139(2): 151-5[Medline].
• Guitet M, Campistol J, Medina M: [Menkes disease: experience in copper salts therapy]. Rev Neurol 1999 Jul 16-31; 29(2): 127-30[Medline].
• Kaler SG, Gallo LK, Proud VK, et al: Occipital horn syndrome and a mild Menkes phenotype associated with splice site mutations at the MNK locus. Nat Genet 1994 Oct; 8(2): 195-202[Medline].
• Kaler SG, Tumer Z: Prenatal diagnosis of Menkes disease. Prenat Diagn 1998 Mar; 18(3): 287-9[Medline].
• Kaler SG, Gahl WA, Berry SA, et al: Predictive value of plasma catecholamine levels in neonatal detection of Menkes disease. J Inherit Metab Dis 1993; 16(5): 907-8[Medline].
• Kaler SG, Goldstein DS, Holmes C, et al: Plasma and cerebrospinal fluid neurochemical pattern in Menkes disease. Ann Neurol 1993 Feb; 33(2): 171-5[Medline].
• Kaler SG: Metabolic and molecular bases of Menkes disease and occipital horn syndrome. Pediatr Dev Pathol 1998 Jan-Feb; 1(1): 85-98[Medline].
• Kaler SG, Buist NR, Holmes CS, et al: Early copper therapy in classic Menkes disease patients with a novel splicing mutation. Ann Neurol 1995 Dec; 38(6): 921-8[Medline].
• Kaler SG, Das S, Levinson B, et al: Successful early copper therapy in menkes disease associated with a mutant transcript containing a small In-frame deletion. Biochem Mol Med 1996 Feb; 57(1): 37-46[Medline].
• Kaler SG: Menkes disease. Adv Pediatr 1994; 41: 263-304[Medline].
• Kaler SG: Menkes disease mutations and response to early copper histidine treatment. Nat Genet 1996 May; 13(1): 21-2[Medline].
• Kaler SG: Diagnosis and therapy of Menkes syndrome, a genetic form of copper deficiency. Am J Clin Nutr 1998 May; 67(5 Suppl): 1029S-1034S[Medline].
• Kaler SG, Schwartz JP: Expression of the Menkes disease homolog in rodent neuroglial cells. Neurosci Res Commun 1998; 23: 61-66.
• Klomp LW, Lin SJ, Yuan DS et al: Identification and functional expression of HAH1, a novel human gene involved in copper homeostasis. J Biol Chem 1997 Apr 4; 272(14): 9221-6[Medline].
• Kodama H, Murata Y, Kobayashi M: Clinical manifestations and treatment of Menkes disease and its variants. Pediatr Int 1999 Aug; 41(4): 423-9[Medline].
• La Fontaine SL, Firth SD, Camakaris J, et al: Correction of the copper transport defect of Menkes patient fibroblasts by expression of the Menkes and Wilson ATPases. J Biol Chem 1998 Nov 20; 273(47): 31375-80[Medline].
• Levinson B, Conant R, Schnur R, et al: A repeated element in the regulatory region of the MNK gene and its deletion in a patient with occipital horn syndrome. Hum Mol Genet 1996 Nov; 5(11): 1737-42[Medline].
• Menkes JHM, Alter M, Steigleder GK: A sex-linked recessive disorder with retardation of growth, peculiar hair and focal cerebellar degeneration. Pediatrics 1962; 29: 764-769.
• Mercer JF, Livingston J, Hall B, et al: Isolation of a partial candidate gene for Menkes disease by positional cloning. Nat Genet 1993 Jan; 3(1): 20-5[Medline].
• Moller LB, Tumer Z, Lund C, et al: Similar splice-site mutations of the ATP7A gene lead to different phenotypes: classical Menkes disease or occipital horn syndrome. Am J Hum Genet 2000 Apr; 66(4): 1211-20[Medline].
• Payne AS, Gitlin JD: Functional expression of the menkes disease protein reveals common biochemical mechanisms among the copper-transporting P-type ATPases. J Biol Chem 1998 Feb 6; 273(6): 3765-70[Medline].
• Petris MJ, Strausak D, Mercer JF: The Menkes copper transporter is required for the activation of tyrosinase. Hum Mol Genet 2000 Nov 22; 9(19): 2845-51[Medline].
• Petris MJ, Mercer JF: The Menkes protein (ATP7A; MNK) cycles via the plasma membrane both in basal and elevated extracellular copper using a C-terminal di-leucine endocytic signal. Hum Mol Genet 1999 Oct; 8(11): 2107-15[Medline].
• Petris MJ, Mercer JF, Camakaris J: The cell biology of the Menkes disease protein. Adv Exp Med Biol 1999; 448: 53-66[Medline].
• Prohaska JR, Tamura T, Percy AK, Turnlund JR: In vitro copper stimulation of plasma peptidylglycine alpha-amidating monooxygenase in Menkes disease variant with occipital horns. Pediatr Res 1997 Dec; 42(6): 862-5[Medline].
• Pufahl RA, Singer CP, Peariso KL, et al: Metal ion chaperone function of the soluble Cu(I) receptor Atx1. Science 1997 Oct 31; 278(5339): 853-6[Medline].
• Robertson D, Goldberg MR, Onrot J, et al: Isolated failure of autonomic noradrenergic neurotransmission. Evidence for impaired beta-hydroxylation of dopamine. N Engl J Med 1986 Jun 5; 314(23): 1494-7[Medline].
• Sarkar B, Lingertat-Walsh K, Clarke JT: Copper-histidine therapy for Menkes disease. J Pediatr 1993 Nov; 123(5): 828-30[Medline].
• Schaefer M, Gitlin JD: Genetic disorders of membrane transport. IV. Wilson's disease and Menkes disease. Am J Physiol 1999 Feb; 276(2 Pt 1): G311-4[Medline].
• Sheela SR, Latha M, Liu P, et al: Copper-replacement treatment for symptomatic Menkes disease: ethical considerations. Clin Genet 2005 Sep; 68(3): 278-83[Medline].
• Suzuki M, Gitlin JD: Intracellular localization of the Menkes and Wilson's disease proteins and their role in intracellular copper transport. Pediatr Int 1999 Aug; 41(4): 436-42[Medline].
• Tumer Z, Horn N, Tonnesen T, et al: Early copper-histidine treatment for Menkes disease. Nat Genet 1996 Jan; 12(1): 11-3[Medline].
• Tumer Z, Moller LB, Horn N: Mutation spectrum of ATP7A, the gene defective in Menkes disease. Adv Exp Med Biol 1999; 448: 83-95[Medline].
• Tumer Z, Lund C, Tolshave J, et al: Identification of point mutations in 41 unrelated patients affected with Menkes disease. Am J Hum Genet 1997 Jan; 60(1): 63-71[Medline].
• Valentine JS, Gralla EB: Delivering copper inside yeast and human cells. Science 1997 Oct 31; 278(5339): 817-8[Medline].
• Voskoboinik I, Strausak D, Greenough M, et al: Functional analysis of the N-terminal CXXC metal-binding motifs in the human menkes copper-transporting P-type ATPase expressed in cultured mammalian cells. J Biol Chem 1999 Jul 30; 274(31): 22008-12[Medline].
• Vulpe C, Levinson B, Whitney S, et al: Isolation of a candidate gene for Menkes disease and evidence that it encodes a copper-transporting ATPase. Nat Genet 1993 Jan; 3(1): 7-13[Medline].

eMedicine Journals > Pediatrics > Genetics And Metabolic Disease > Menkes Kinky Hair Disease

Please email us with any comments you have on our new chapter format.

Author Information | Introduction | Clinical | Workup | Treatment | Medication | Follow-up | Miscellaneous | Test Questions | Pictures | Bibliography