Menkes Disease

A number sign (#) is used with this entry because of evidence that Menkes disease is caused by mutation in the gene encoding Cu(2+)-transporting ATPase, alpha polypeptide (ATP7A; 300011). The occipital horn syndrome (304150) is caused by mutation in the same gene.

Description

Menkes disease is an X-linked recessive disorder characterized by generalized copper deficiency. The clinical features result from the dysfunction of several copper-dependent enzymes.

De Bie et al. (2007) provided a detailed review of the molecular pathogenesis of Menkes disease.

Clinical Features

In a family of English-Irish descent living in New York, Menkes et al. (1962) described an X-linked recessive disorder characterized by early retardation in growth, peculiar hair, and focal cerebral and cerebellar degeneration. Severe neurologic impairment began within a month or two of birth and progressed rapidly to decerebration. Five males were affected but the gene could by inference be identified in 4 generations. The failure to grow brought the affected infants to medical attention at the age of a few weeks and death occurred in the first or second year of life. The hair was stubby and white. Microscopically it showed twisting, varying diameter along the length of the shaft, and often fractures of the shaft at regular intervals. Rather extensive biochemical investigations showed elevated plasma glutamic acid as the only consistent abnormality. The anatomic change in the central nervous system was described on the basis of 2 autopsies.

Bray (1965) observed 2 brothers who died as infants with spastic dementia, seizures, and defective hair. Blood and urine amino acids were normal. Whether this is the same disorder as that in Menkes' family was unclear. The condition described by Yoshida et al. (1964) may have been the same. French and Sherard (1967) presented evidence that they interpreted as indicating that this disorder may represent an abnormality of lipid metabolism. Their 16-month-old patient showed: (1) scant, whitish, lackluster, kinky hair that microscopically showed pili torti, monilethrix and trichorrhexis nodosa; (2) retarded growth; (3) micrognathia and highly arched palate; (4) decline in mental development; (5) onset of focal and generalized seizures; and (6) spastic quadriparesis with clenched fists, opisthotonos, and scissoring. Biochemical studies showed depressed serum tocopherol and normal amino acid content of hair serum and urine. An abnormal autofluorescence is displayed by hair and by Purkinje cells' axons.

'Kinky hair disease' proved a designation useful in detection of new cases, since the hair change is an easily remembered feature by which physicians can be alerted to the condition (O'Brien, 1968). Changes in the metaphyses of the long bones and tortuosity of cerebral arteries have been described. Hypothermia and acute illness with septicemia were modes of presentation. Patchy abnormality of systemic arteries with stenosis or obliteration was observed by Danks et al. (1971). They also observed toluidine-blue-metachromasia of fibroblasts. Wesenberg et al. (1969) pointed out that the fetal hair does not show pili torti.

Goka et al. (1976) found that cultured fibroblasts have a concentration of copper over 5 times that of normal fibroblasts. Williams et al. (1978) described the cellular pathology of Menkes disease.

Osaka et al. (1977) reported 2 Japanese families. They pointed out that the hair may not be abnormal, that serum copper determination is a simple and reliable diagnostic test, and that 'congenital hypocupraemia' may be a preferred designation. An abnormality in egress of copper from Menkes disease fibroblasts was suggested by studies of Chan et al. (1978). Defective metallothionein (see 156530) was suggested.

Haas et al. (1981) reported an X-linked disorder of copper metabolism which, by my interpretation, may be an allelic variant of Menkes syndrome. The disorder affected 4 males in 3 sibships connected through females. Similarities to Menkes disease were X-linked recessive inheritance, marked psychomotor retardation with seizures, low serum copper and ceruloplasmin (117700) levels, and a block in gut copper absorption. Differences from Menkes disease included normal birth weight, no hypothermia, grossly and microscopically normal hair, and radiographically normal bones. Survivorship was much longer than in Menkes disease. The neurologic disorder was static and characterized by hypotonia and choreoathetosis.

Tonnesen et al. (1991) reviewed the cases of atypical Menkes reported by Haas et al. (1981). No pili torti were found in one case and very few (2 in 1,000) in a second. In addition, low levels of copper and ceruloplasmin in the serum were puzzling findings. However, (64)Cu uptake and retention was significantly increased in the range seen for classic Menkes patients, and copper uptake in female relatives gave the same uptake pattern as in heterozygotes in other families with the classic disorder.

Godwin-Austen et al. (1978) described a disorder clinically reminiscent of Wilson disease but without Kayser-Fleischer rings. Symptoms began at age 12 years and defective copper absorption from the distal intestine, with high copper levels in rectal mucosa, was demonstrated. X-linked inheritance was suggested.

Proud et al. (1996) reported on the clinical features of 4 affected persons in 3 generations of a family that manifested an unusual variant of the Menkes syndrome. These patients had normal head circumference, moderate to severe mental retardation, onset at age of 3 to 4 years, dysarthria, laxity of skin, bladder diverticula, tortuous vessels, chronic diarrhea, and occipital exostoses (evident in 3 persons aged 18 to 38 years). Study of the MNK gene showed an A-to-T change at the +3 position of the splice donor site near the 3-prime end of the MNK coding sequence resulting in abnormal splicing (Kaler et al., 1994). The authors proposed that maintenance of 20% of normal splicing could explain unique phenotypic manifestations in affected persons. Proud et al. (1996) suggested that these patients, as well as a patient with occipital horn syndrome reported by Wakai et al. (1993), represent a new variant of Menkes syndrome. Phenotypic overlap between Menkes syndrome and the occipital horn syndrome (304150) is to be expected since both are caused by mutations in the ATP7A gene (300011).

Gerard-Blanluet et al. (2004) described occipital horns in a classic case of Menkes disease caused by an 8-bp deletion in the ATP7A gene (300011.0011). They pointed out that 'occipital horn' refers to a wedge-shaped calcification that forms within the tendinous insertions of the trapezius and sternocleidomastoid muscles at their attachment to the occipital bone. They suggested that presence of voluntary traction on these hyperlax tendons attached to the skull could then have provoked calcification of the occipital tendons as an aberrant way of reparation. Gerard-Blanluet et al. (2004) suggested that voluntary traction of the relevant muscles persisting after 2 years of age, needing both sustained voluntary head control and long survival, is required for the development of occipital horns in patients with Menkes disease caused by a deleterious mutation in the ATP7A gene.

Jankov et al. (1998) described a newborn male who presented with acute onset of severe intraabdominal bleeding, hemorrhagic shock, and multiple fractures leading to death on day 27. Menkes disease was diagnosed at autopsy and confirmed by copper accumulation studies on cultured fibroblasts. Such an early onset of fatal complications in Menkes disease had not previously been reported. The mutation in this case was said to have been identical to that found in an unrelated male with Menkes disease who died at the age of 4 years without severe connective tissue disease. Horn (1999) reported that the mutation in ATP7A was arg980 to ter (300011.0005).

Tumer and Horn (1997) reviewed the clinical and genetic aspects of Menkes syndrome, including phenotypic expression in females, mutation spectrum, diagnosis, and treatment. They also discussed the mottled mouse as a model for Menkes syndrome and new insights into normal and defective copper metabolism provided by biochemical and genetic studies of Menkes syndrome and Wilson disease (277900).

Female Carriers

Smpokou et al. (2015) reported 3 unrelated girls who presented in infancy with clinical features of Menkes disease. Features were somewhat variable, but included hypotonia, myopathic facies, coarse hair, silvery hair, skin and joint laxity, and severe global developmental delay. All had cerebrovascular tortuosity and brain or cerebellar atrophy. Two patients had seizures. Serum copper levels were decreased in 2 patients and low-normal in the third patient. Two patients were treated with copper without a clear benefit to cognitive development, although 1 of the patients who received treatment did not develop seizures. The report indicated that females with Menkes disease can have significant manifestations of the disorder.

Biochemical Features

Danks et al. (1972) presented evidence of a defect in the intestinal absorption of copper. Copper deficiency in animals leads to connective tissue changes because formation of lysine-derived cross-links in elastin and collagen is interfered with, the amine oxidase responsible for the initial modification of lysine being copper-dependent. This may explain the arterial abnormalities. The striking hair changes are probably the result of defective formation of disulfide bonds in keratin since this process is copper-dependent, and copper deficiency in sheep leads to the formation of wool with defective cross-linking (Collie et al., 1980). Menkes had sent hair from his original patients to the Australian Wool Commission, but at that early date the Commission could not identify the problem (Menkes, 1972).

Peltonen et al. (1983) found many similar abnormalities of copper and collagen metabolism in the cultured fibroblasts of 13 patients with Menkes syndrome and 2 patients with E-D IX. In both disorders, fibroblasts had markedly increased copper content and rate of incorporation of (64)Cu, and accumulation was in metallothionein (see 156350) or a metallothionein-like protein as previously established for Menkes cells. Histochemical staining showed that copper was distributed uniformly throughout the cytoplasm in both cell types, this location being consistent with accumulation in metallothionein. Both fibroblast types showed very low lysyl oxidase activity and increased extractability of newly synthesized collagen, but no abnormality in cell viability, duplication rate, prolyl 4-hydroxylase activity, or collagen synthesis rate. Skin biopsy specimens from one E-D IX patient showed the same abnormalities in lysyl oxidase activity and collagen extractability. Fibroblasts of the mother of E-D IX patients showed increased (64)Cu incorporation. The similarities in biochemical findings between type IX Ehlers-Danlos syndrome and Menkes syndrome may indicate allelism. In studies of cultured cells from both conditions, Kuivaniemi et al. (1985) could not demonstrate that there was secreted into the medium or contained in the cell any significant amounts of copper-deficient, catalytically inactive lysyl oxidase protein. Although the rapid degradation of a mutant protein could not be excluded, the authors favored the idea that synthesis of the lysyl oxidase protein is impaired.

Scheinberg and Collins (1989) suggested that the primary defect resides in zinc, i.e., that Menkes disease is primarily a disorder of a putative zinc-binding protein, which they symbolized ZBP, whose synthesis is controlled by a gene on the X chromosome. When ionic zinc is present in the liver or intestine it induces the synthesis of metallothionein to which the zinc is bound. Since the affinity of metallothionein for copper is 100,000 times greater than that for zinc, copper in either organ displaces zinc and binds to metallothionein. In the liver such bound copper is probably unavailable for incorporation into specific copper 'apo' proteins. In the intestine copper does not enter the circulation; advantage has been taken of this fact to decrease the intestinal absorption of copper by administering zinc in Wilson disease (277900). Deficiency of ZBP in Menkes disease would presumably result in an increased concentration of nonprotein-bound, ionic zinc--the only form of the element that has been shown to induce synthesis of metallothionein.

Other Features

Menkes (1988) gave a useful review in which he listed 6 cuproenzymes, 5 of which may account for features of the disorder: tyrosinase for depigmentation of hair and skin pallor; lysyl oxidase for frayed and split arterial intima (defect in elastin and collagen cross-linking); monoamine oxidase for kinky hair; cytochrome c oxidase for hypothermia; and ascorbate oxidase for skeletal demineralization. Dopamine-beta-hydroxylase is also a cuproenzyme; what role its deficiency may have in the phenotype of kinky hair disease is unclear.

Cytogenetics

Gerdes et al. (1990) described 3 patients with clinically and biochemically typical Menkes syndrome; a chromosome abnormality was found in only 1 (45X/46XX mosaicism). During a systematic chromosomal survey of 167 unrelated boys with Menkes disease, Tumer et al. (1992) found a unique rearrangement of the X chromosome involving an insertion of the long arm segment Xq13.3-q21.2 into the short arm at band Xp11.4, giving the karyotype 46,XY,ins(X)(p11.4q13.3q21.2). The same rearranged X chromosome was present de novo in the boy's phenotypically normal mother, where it was preferentially inactivated. RFLP and methylation patterns at DXS255 indicated that the rearrangement originated from the maternal grandfather. This finding supported localization of the MNK locus to Xq13 and suggested fine mapping to subband Xq13.3. The chromosomal band associated with the X-inactivation center (XIC; 314670) was present, in this patient, on the proximal long arm of the rearranged X chromosome, in line with the location of XIC proximal to MNK.

Mapping

Wieacker et al. (1983) performed linkage studies in a large kindred with Menkes syndrome using a cloned DNA sequence (RFLP), probe 1.28, that maps to the proximal portion of Xp (between Xcen and Xp113). At least 2 crossovers and an estimated genetic distance of 16 cM were found (lod score = 0.82). Horn et al. (1984) demonstrated linkage between Menkes disease and a centromeric C-banding polymorphism. Other studies of linkage with 2 RFLPs, MGU22 (which is close to the centromere) and L1.28 (which is in the Xp110-Xp113 segment), suggested that the Menkes locus is distal to L1.28 (review by Ropers et al., 1983).

Wienker et al. (1983) suggested the following as the most likely gene order: Xpter--MS--L1.28--MGU22. Comparative mapping suggested to Horn et al. (1984) that the Menkes disease locus is on the long arm close to band q13; on the mouse X-chromosome the homologous Mo locus ('mottled') is located between the structural loci for phosphoglycerate kinase (Pgk-1) and alpha-galactosidase (Ags), closely linked to the Pgk-1 locus, the human equivalent of which, PGK, has been assigned to Xq13. Linkage studies in 5 Dutch families suggested close situation of the Menkes locus and the centromere (recombination fraction 0.5, lod score more than 3.0). Centromeric heteromorphism was used as the 'marker trait.' There was probably no detectable linkage with Xg.

From a 3-point analysis, Tonnesen et al. (1986) concluded that the Menkes locus is on the long arm of the X chromosome proximal to DXYS1. In studies of 4 families in which a characteristic X-centromeric marker was segregating with Menkes disease, Friedrich et al. (1983) found only 1 recombinant out of 18 opportunities, indicating that the gene is near the centromere on either the long arm or the short arm. Kapur et al. (1987) suggested that the Menkes syndrome gene may lie in the Xq13 band because of the finding of Menkes syndrome in a female with a de novo balanced translocation t(2;X). The breakpoint in the X chromosome was at Xq13.1.

Verga et al. (1991) refined the localization of the MNK locus. They established a lymphoblastoid cell line from the patient of Kapur et al. (1987) and used it to isolate the der(2) translocation chromosome in human/hamster somatic cell hybrids. Southern blot analyses using a number of probes specific for chromosomes X and 2 showed that the breakpoint in this patient--and, therefore, probably the Menkes gene--mapped to a small subregion of band Xq13.2-q13.3 proximal to the PGK1 (311800) locus and distal to all other Xq13 loci tested. Hershon (1988) concluded from study of an X/A translocation that the locus lies near the boundary between Xq12 and Xq13, probably at Xq13.1.

Tonnesen et al. (1992) reported on linkage analyses in 11 families in which more than one affected patient had been found. They concluded that the most likely location of MNK is Xq12-q13.3. Working with DNA from the cells from the patient with the translocation t(2;X) reported by Kapur et al. (1987), Consalez et al. (1992) developed a cosmid contig extending 150 kb from a nearby CpG island across the breakpoint on the X chromosome (see erratum indicating additional information on the location of the translocation breakpoint).

Sugio et al. (1998) described a Japanese girl with Menkes disease due to a de novo X;21 reciprocal translocation in which a breakpoint at Xq13.3 had disrupted the ATP7A gene. They demonstrated that the normal X chromosome was late replicating, whereas the derivative X chromosome was selectively early replicating.

Abusaad et al. (1999) reported a female with typical manifestations of Menkes disease who carried a de novo balanced translocation 46,X,t(X;13)(q13.3;q14.3). The diagnosis was confirmed by findings of low levels of serum copper and ceruloplasmin with increased copper uptake in cultured fibroblasts. The authors hypothesized that function of the ATP7A gene had been disrupted by the translocation, either by a structural disruption or by 'silencing' as a result of inappropriate localized inactivation in an otherwise active X;13 derivative chromosome.

Molecular Genetics

Three independent groups, in San Francisco (Vulpe et al., 1993), Oxford (Chelly et al., 1993), and Michigan (Mercer et al., 1993), cloned a candidate gene for Menkes disease. Vulpe et al. (1993), who proceeded directly from the translocation breakpoints at Xq13.3 to the gene by cDNA library screening with a YAC fragment and exon trapping experiments, succeeded in obtaining a complete set of clones corresponding to an 8.5-kb transcript that encodes a 1,500 amino acid protein. The 5-prime region of the same locus was also obtained by Chelly et al. (1993) who took the more cumbersome but genetically rigorous step of first identifying genomic fragments that were deleted in cytogenetically normal patients with Menkes disease, and by Mercer et al. (1993) who employed a strategy involving long range restriction mapping and fluorescence in situ hybridization (FISH) analysis. Two lines of evidence strongly implicated the cloned MNK locus in the etiogenesis of Menkes disease: nonoverlapping portions of the gene were deleted in 16 of 100 unrelated patients (Chelly et al., 1993), and the expression of the transcript was reduced or altered in 23 of 32 patients (Vulpe et al., 1993; Mercer et al., 1993). By a database search of the predicted sequence, Vulpe et al. (1993) found strong homology to P-type ATPases, a family of integral membrane proteins that use an aspartyl phosphate intermediate to transport cations across membranes. The protein has the characteristics of a copper binding protein. Northern blot experiments showed that MNK mRNA is present in a variety of cell types and tissues except liver, in which expression is reduced or absent. This is consistent with the clinical observation that the liver is largely unaffected in Menkes disease and fails to accumulate excess copper.

The MNK protein is localized to the trans-Golgi network (TGN) (Petris et al., 1996). Studies with copper-resistant Chinese hamster ovary cells (CHO) by Petris et al. (1996) suggested that the MNK protein cycles between the TGN and the plasma membrane, depending on the concentration of copper within the cell. TGN38 (603062) is another protein that cycles between the TGN and the plasma membrane (Ladinsky and Howell, 1992; Reaves et al., 1993). A number of Golgi-resident proteins contain specific localization signals, and Francis et al. (1998) showed that this is true also of MNK. By immunofluorescence, they showed that the full-length recombinant Menkes protein, the isoform that is not expressed in the occipital horn syndrome, localizes to the Golgi apparatus, whereas the alternatively spliced form, which lacks sequences for transmembrane domains 3 and 4 encoded by exon 10 and is expressed in the occipital horn syndrome, localizes to the endoplasmic reticulum. Using sequences from exon 10 fused to a non-Golgi reporter molecule, Francis et al. (1998) showed that a 38-amino acid sequence containing transmembrane domain 3 of the MNK protein was sufficient for localization to the Golgi complex. Therefore, the protein sequence encoded by exon 10 may be responsible for this differential localization and both isoforms may be required for comprehensive transport of copper within the cell. By immunogold electron microscopic analyses, La Fontaine et al. (1998) mapped the MNK protein to the TGN. When the extracellular copper concentration was increased, MNK in the CHO cells was redistributed to the cytoplasm and plasma membrane, but returned to the TGN under basal, low copper conditions.

The MNK protein is normally localized predominantly in the TGN; however, when cells are exposed to excessive copper it is rapidly relocalized to the plasma membrane where it functions in copper efflux. Petris and Mercer (1999) found that in cells stably expressing tagged MNK protein, extracellular antibodies were internalized to the perinuclear region, indicating that the tagged MNK at the TGN constitutively cycles via the plasma membrane in basal copper conditions. Under elevated copper conditions, the tagged MNK was recruited to the plasma membrane; however, internalization of the tagged protein was not inhibited, and the protein continued to recycle through cytoplasmic membrane compartments. These findings suggested that copper stimulates exocytic movement of MNK to the plasma membrane rather than reducing MNK retrieval and indicated that MNK may remove copper from the cytoplasm by transporting copper into the vesicles through which it cycles.

Screening 383 unrelated patients affected with Menkes syndrome, Tumer et al. (2003) found 57 with gross deletions in the ATP7A gene (14.9%). Except for a few cases, gross gene deletions resulted in a classic form of Menkes disease with death in early childhood.

Moller et al. (2005) identified 21 novel missense mutations in the ATP7A gene in patients with Menkes disease. The mutations were located within the conserved part of ATP7A between residues val842 and ser1404. Molecular 3-dimensional modeling based on the structure of ATP2A1 (108730) showed that the mutations were more spatially clustered than expected from the primary sequence. The authors suggested that some of the mutations may interfere with copper binding.

Diagnosis

Carrier status for the Menkes disease gene can usually be determined by examination of multiple hairs from scattered scalp sites for pili torti. Carrier status can, of course, never be completely excluded by negative findings of such scrutiny. Moore and Howell (1985) found pili torti in all affected males and in 43% of 28 obligate carriers or females at risk. When present, pili torti can be considered, in their opinion, a reliable indicator of heterozygosity. Changes in the metaphyses of the long bones resemble scurvy. Ascorbic acid oxidase is copper-dependent. Tumer et al. (1994) described first trimester prenatal diagnosis of Menkes disease using a specific DNA probe.

Clinical Management

Williams et al. (1977) discussed studies of metabolism and long-term copper therapy in Menkes disease. Sander et al. (1988) described a patient who survived to the age of 13.5 years. Most patients have died between the ages of 6 months and 3 years. The administration of copper may have helped in the survival. In studies by De Groot et al. (1989), vitamin C therapy was ineffective. Procopis et al. (1981) described a mild, presumably allelic form. They urged that mentally retarded or ataxic boys with pili torti be investigated with this disorder in mind. Westman et al. (1988) described a second child with the atypical form who had survived to age 9 years and was doing well clinically. Danks (1988) reported on the progress of the patient reported by Procopis et al. (1981). By then aged 10 years, the patient had been treated for many years with injections of copper histidinate. Ataxia and dysarthria had been the principal problems. No radiologic abnormalities had developed in the skull or limb bones; in particular, no 'occipital horn' was discerned.

Sherwood et al. (1989) found excellent results from subcutaneous copper histidinate therapy in 2 unrelated boys with classic Menkes disease. Copper histidinate is probably the form in which copper crosses the blood-brain barrier (Hartter and Barnea, 1988). One of the patients developed orthostatic hypotension such that he preferred to crouch rather than stand. The other patient had 2 massive bladder diverticula.

Whereas parentally administered copper in the form of copper sulfate or copper-EDTA probably does not produce a substantial clinical improvement, Tumer et al. (1996) found evidence for the efficacy of copper-histidine, which is naturally present in the serum and is quantitatively important in copper transport. Copper-histidine appeared to be ineffective when it was given after the first few months of life. However, in 2 unrelated patients with this disorder who were born prematurely and received early copper-histidine treatment, the response was favorable (see Sherwood et al. (1989) and Sarkar et al. (1993)). At the time of the Tumer et al. (1996) report, these patients were aged 19 and 9 years and presented with a milder clinical course, mainly characterized by connective tissue abnormalities resembling the occipital horn syndrome (304150). An unresolved question concerned the severity of the disease in each case. One of the patients had a positive family history suggesting that he was liable to the severe form, but the possibility of intrafamilial clinical variation could not be excluded. To clarify these questions, Tumer et al. (1996) characterized the genetic defects in the ATP7A gene. Using a combination of single-strand conformation analysis and direct sequencing of amplified exons, they detected a single bp deletion in exon 4 in one patient and in exon 12 in the other. Both mutations led to a frameshift and created a premature termination codon within the same exon. RT-PCR analysis of total fibroblast RNA of both patients showed no evidence of exon skipping, indicating that the mutation resulted in severely truncated proteins. They concluded that the disorder would be expected to be severe and that the therapy had been effective. A newspaper photograph of the 9-year-old patient indicated his appearance at the time of the report.

Christodoulou et al. (1998) described the long-term clinical course of 4 boys who had Menkes disease treated from early infancy with parenteral copper-histidine, with follow-up over 10 to 20 years. Male relatives of 3 of the 4 had a severe clinical course compatible with classic Menkes disease. As a consequence of early treatment, their patients had normal or near-normal intellectual development, but developed many of the more severe somatic abnormalities of the related disorder occipital horn syndrome, including severe orthostatic hypotension in 2. In addition, 1 boy developed a previously unreported anomaly: massive splenomegaly and hypersplenism as a consequence of a splenic artery aneurysm. The oldest patient was 20 years of age at the time of report. Hypotension had been a problem from the age of 14 years. A syncopal episode on standing was associated with bradycardia. Treatment with atropine resulted in a brisk increase in heart rate and rapid clinical recovery. There was no increase in blood pressure following immersion of the hand in ice-cold water, or following a mental arithmetic challenge, suggesting that his postural hypotension may have an autonomic basis. It was subsequently treated with a peripheral alpha-adrenergic agonist, midodrine, in combination with fludrocortisone. He suffered from persistent chronic diarrhea since early infancy.

Kanumakala et al. (2002) evaluated the bone mineral density (BMD) changes following pamidronate treatment in children with Menkes disease. Three children with Menkes disease and significant osteoporosis with or without pathologic fractures all received pamidronate treatment for 1 year. There were 34 to 55% and 16 to 36% increases in lumbar spine bone mineral content and areal bone mineral density, respectively, following 1 year of treatment with pamidronate. There were no further fractures in 2 of the 3 children treated. No adverse effects of pamidronate treatment were noted. Kanumakala et al. (2002) suggested that pamidronate may be an effective treatment modality for the management of osteoporosis in children with Menkes disease.

Olivares et al. (2006) reported a 9-year-old boy with Menkes disease who had been treated with subcutaneous copper-histidine since age 12 months. Although treatment did not prevent severe growth and mental retardation, it normalized plasma levels of copper and ceruloplasmin, improved his muscular tone, motor activity, and irritability, and most importantly, he never developed seizures. The patient had a missense mutation in the ATP7A gene, which the authors hypothesized may have resulted in better response to therapy than a more deleterious mutation.

Population Genetics

Danks et al. (1971) suggested that the frequency may be 1 in 40,000 live births in Melbourne and higher than previously thought because some patients may die undiagnosed.

Tonnesen et al. (1991) estimated that the combined frequency of live-born Menkes disease patients in Denmark, France, the Netherlands, the United Kingdom, and West Germany was 1 per 298,000 live-born babies in the period 1976 to 1987. They estimated the mutation rate for Menkes disease to be 1.96 x 10(-6), based on the number of isolated Menkes cases born during that period.

Animal Model

The mottled series of mutations in the mouse may be homologous to Menkes syndrome (Hunt, 1974). The 'mottled' mutation in the hamster is also probably homologous (Yoon, 1973). Brophy et al. (1988) studied aortic aneurysm in the 'blotchy' mouse, one of the mottled series of mutations. Affected animals had a progressive increase in the instance of aneurysms with age, reaching 100% within 6 months. Most aneurysms occurred in the ascending aorta, with some also present in the descending thoracic and abdominal segments. Some animals had multiple aneurysms.

George et al. (1994) analyzed mouse Mnk, a murine locus homologous to Menkes disease, in both normal mice and those with the mottled phenotype.

Male mice with the Mottled-Brindled allele accumulate copper in the intestine, fail to export copper to peripheral organs, and die a few weeks after birth. Much of the intestinal copper found in Mottled-Brindled mice is bound by metallothionein (MT); see 156350. To determine the function of MT in the presence of Atp7a deficiency, Kelly and Palmiter (1996) crossed Mottled-Brindled females with males that bear a targeted disruption of the Mt1 and Mt2 genes. On the metallothionein-deficient background most Mottled males as well as heterozygous Mottled females died before embryonic day 11. The authors explained the lethality in females by preferential inactivation of the paternal X chromosome in extra embryonic tissues and resultant copper toxicity in the absence of MT. In support of this hypothesis, Kelly and Palmiter (1996) found that cell lines derived from metallothionein deficient, Mottled embryos were very sensitive to copper toxicity. They concluded that MT is essential to protect against copper toxicity in embryonic placenta, providing a second line of defense when copper effluxers are defective. They also stated that MT probably protects against hepatic copper toxicity in Wilson disease and the LEC rat model in which a similar copper effluxer, ATP7B (606882), is defective, because MT accumulates to high levels in the liver in those diseases.

The nature of the mutation in the brindled mouse is of importance in understanding the normal role of the protein encoded by ATP7A and for devising treatment strategies for Menkes disease. Grimes et al. (1997) showed that the brindled mouse has a deletion of 2 amino acids in a highly conserved, but functionally uncharacterized, region of the Atp7a gene. They also presented Western blot data for the normal gene product in tissues. In the kidney, immunohistochemistry demonstrated the protein in proximal and distal tubules, with a distribution identical in mutant and normal mice. This distribution was considered consistent with the protein being involved in copper resorption from the urine.

Masson et al. (1997) studied copper uptake and retention in fibroblast cultures established from 4 independent mottled alleles associated with postnatal male survival, 5 independent mottled alleles associated with prenatal death of affected males, and 12 controls. Both groups of mutants were separable from controls on both copper uptake and copper retention assays. Values obtained were the same as those previously reported for human fibroblasts established from patients with Menkes disease, but no significant differences were found between the alleles associated with survival and those associated with prenatal death.