Type X

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From Genetics Home Reference: Your guide to understanding genetic conditions

(A service of the U.S. National Library of Medicine)

What is Charcot-Marie-Tooth disease, type X?

Type X Charcot-Marie-Tooth disease is a progressive disorder that affects

peripheral nerves. These nerves connect the brain and spinal cord to muscles as

well as sensory cells that detect sensations such as touch, pain, heat, and

sound. Type X is characterized by changes in a gene on the X chromosome (one of

the two sex chromosomes) and more severe symptoms in males than females.

Charcot-Marie-Tooth disease, type X is a subtype of Charcot-Marie-Tooth disease.

The symptoms associated with type X Charcot-Marie-Tooth disease usually begin

between 5 and 25 years of age but may occur anytime from infancy to after age

30. Symptoms vary in severity; some people never realize they have the disorder,

while a small percentage experience significant disability. Generally, males

experience moderate to severe symptoms beginning in childhood or early

adolescence, and females have milder symptoms that begin during adolescence or

adulthood. Most people with this disorder lead active lives and have normal life

expectancies.

Typically, the earliest symptoms involve muscle weakness in the feet and lower

legs, which can affect a person's manner of walking (or gait). Later symptoms

may include hand weakness and the loss of sensation, such as the inability to

perceive touch, pain, and temperature changes. In some cases, sensory loss

includes hearing impairment and deafness. (Additional information on symptoms is

available in the overview summary of Charcot-Marie-Tooth disease.)

How common is Charcot-Marie-Tooth disease, type X?

Type X Charcot-Marie-Tooth disease is estimated to occur in 4 to 8 per 100,000

individuals.

What genes are related to Charcot-Marie-Tooth disease, type X?

Mutations in the GJB1 gene cause Charcot-Marie-Tooth disease, type X.

The consequences of a mutation in the GJB1 gene are not clearly understood.

Mutations in this gene probably disturb the function of specialized cells that

produce myelin to cover and protect nerves. As a result of this disrupted

function, nerve cells slowly lose the ability to communicate with muscles and to

transmit sensory signals.

How do people inherit Charcot-Marie-Tooth disease, type X?

This condition is inherited in an X-linked dominant pattern. A condition is

considered X-linked if the gene that causes the disorder is located on the X

chromosome (one of the two sex chromosomes). The inheritance is dominant if one

copy of the altered gene is sufficient to cause the condition. In most cases,

males experience more severe symptoms of the disorder than females. A striking

characteristic of X-linked inheritance is that fathers cannot pass X-linked

traits to their sons.

Where can I find information about Charcot-Marie-Tooth disease, type X?

You may find the following resources about Charcot-Marie-Tooth disease, type X,

helpful.

a.. NIH Publications - National Institutes of Health

National Institute of Neurological Disorders and Stroke

b.. MedlinePlus - Health Information (2 links)

c.. Educational resources - Information pages (2 links)

d.. Patient support - For patients and families (4 links)

You may also be interested in these resources, which are designed for healthcare

professionals and researchers.

a.. Gene Reviews - Clinical summary

b.. Gene Tests - DNA tests ordered by healthcare professionals

c.. PubMed - Recent literature

d.. OMIM - Genetic disorder catalog

What other names do people use for Charcot-Marie-Tooth disease, type X?

a.. Charcot-Marie-Tooth disease, X-linked

b.. Charcot-Marie-Tooth neuropathy, type X

c.. Charcot-Marie-Tooth peroneal muscular atrophy, X-linked

d.. CMT

e.. CMTX

f.. CMTX1

g.. hereditary motor and sensory neuropathy, X-linked

h.. HMSN, X-linked

See How are genetic conditions and genes named? in the Handbook.

What if I still have specific questions about Charcot-Marie-Tooth disease, type

X?

a.. See How can I find a genetics professional in my area? in the Handbook.

b.. Ask the Genetic and Rare Diseases Information Center.

Where can I find general information about genetic conditions?

The Handbook provides basic information about genetics in clear language.

a.. What does it mean if a disorder seems to run in my family?

b.. What are the different ways in which a genetic condition can be inherited?

c.. If a genetic disorder runs in my family, what are the chances that my

children will have the condition?

d.. Why are some genetic conditions more common in particular ethnic groups?

These links provide additional genetics resources that may be useful.

a.. Genetics and health

b.. Resources for Patients and Families

c.. Resources for Health Professionals

What glossary definitions help with understanding Charcot-Marie-Tooth disease,

type X?

atrophy ; chromosome ; gait ; gene ; mutation ; nerve cell ; neuropathy ;

peripheral nerves ; sensory cells ; symptom ; X-linked dominant

You may find definitions for these and many other terms in the Genetics Home

Reference Glossary.

References (5 links)

The resources on this site should not be used as a substitute for professional

medical care or advice. Users seeking information about a personal genetic

disease, syndrome, or condition should consult with a qualified healthcare

professional. See How can I find a genetics professional in my area? in the

Handbook.

Last Comprehensive Review: November 2004

Published: January 24, 2005