Rare Dermatology News

Disease Profile

X-linked Charcot-Marie-Tooth disease

Prevalence
Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.
1-9 / 100 000

3,310 - 29,790

US Estimated

1-9 / 100 000

5,135 - 46,215

Europe Estimated

Age of onset

-

ICD-10

G60.0

Inheritance

Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease

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Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype

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X-linked
dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.

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X-linked
recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder

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Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.

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Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.

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Not applicable

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Other names (AKA)

CMTX; X-linked hereditary motor and sensory neuropathy

Summary

The following summary is from Orphanet, a European reference portal for information on rare diseases and orphan drugs.
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Orpha Number: 64747

Definition
A disorder that belongs to the genetically heterogeneous group of CMT peripheral sensorimotor polyneuropathy diseases.

Clinical description
CMTX1 is characterized by a slowly progressive course: muscle wasting and weakness of distal limb muscles mainly involving the feet, legs and hands (particularly the thenar eminence), with proximal muscle weakness occurring in severe cases; distal sensory loss; loss of deep tendon reflexes; pes cavus and more rarely scoliosis. Rare instances of transient central nervous system (CNS) dysfunction have been described, with dysarthria, dysphagia, weakness, ataxia, and even aphasia and somnolence. All forms of CMTX are rare and are characterized by intellectual deficit (CMTX2, CMTX4), spastic paraplegia (CMTX3), hearing loss (CMTX4, CMTX5, rarely CMTX1), and optic atrophy (CMTX5).

Etiology
CMTX1 is associated with mutations in the GJB1 gene (Xq13.1), encoding connexin 32 (Cx32). Cx32 forms gap-junctions in non-compact myelin produced by myelinating Schwann cells. Cx32 is also expressed in oligodendrocytes, explaining the potential CNS involvement. CMTX5 is associated with mutations in the phosphoribosylpyrophosphate synthetase 1 gene (PRPS1). CMTX1 is transmitted as an X-linked dominant trait and males are more severely affected than females, whereas the other CMTX types are X-linked recessive and female carriers are usually unaffected.

Diagnostic methods
Diagnosis is based on family and personal history, clinical examination, nerve conduction studies (NCS), and DNA testing (for CMTX1). NCS show a sensorimotor polyneuropathy with decreased conduction velocities in males (usually in the intermediate range of 30-45 m/s in upper limb motor nerves) and mildly decreased or even normal velocities in females. In contrast with other CMT types, conduction slowing is frequently nonhomogeneous, with temporal dispersion and sometimes conduction blocks, and the median nerve being more severely affected than the ulnar nerve. Nerve biopsy reveals prominent axonal changes, in spite of nerve conduction slowing, with evidence of ultrastructural abnormalities in the paranodal regions. Auditory evoked potentials usually reveal abnormalities of central waves in the brainstem, consistent with frequent subclinical brain involvement in CMTX1.

Differential diagnosis
Differential diagnosis includes other CMT types and acquired dysimmune neuropathies such as chronic inflammatory demyelinating polyradiculoneuropathy (see these terms).

Antenatal diagnosis
Prenatal diagnosis is possible for CMTX1 when the mutation is known.

Genetic counseling
As an X-linked dominant trait, there is no male-to-male transmission; female carriers are usually mildly affected and have a 50% risk of transmitting the disease to their offspring.

Management and treatment
There is no drug treatment available. Rehabilitation therapy and surgical treatment of skeletal deformities are the only options.

Prognosis
CMTX1 is moderately severe for affected males, who may loose ambulation capacity later in life.

Visit the Orphanet disease page for more resources.

Organizations

Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

Organizations Supporting this Disease

    Learn more

    These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

    In-Depth Information

    • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
    • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.