On the cover: TyKiah Wright of Columbus, Ohio, has been affected by CMT since childhood. Now 31, she earned bachelor’s and MBA degrees from Wright State University in Dayton. In 2001, she established the WrightChoice Intern Program, which helps minority students and students with disabilities find internships and jobs.

Dear Friends What is Charcot-Marie-Tooth Disease? What causes CMT? What happens to someone with CMT, and how is it treated? What are the different types of CMT? How is CMT diagnosed? Does it Run in the Family? MDA’s Search for Treatments & Cures MDA is Here to Help You

Does it Run in the Family?

CMT can run in a family, even when there’s no obvious family history of it. In part, this is because CMT can be inherited in three different ways that aren’t always easy to trace through a family tree: X-linked, autosomal dominant and autosomal recessive.

X-linked means that the genetic defect (or mutation) is located on the X chromosome. In females, who have two X chromosomes, a normal copy of the gene on one chromosome can often compensate (at least partially) for the defective copy. Therefore, X-linked diseases usually affect males more severely than females, beccause males only have one X chromosome. X-linked diseases (like CMTX) can’t be passed from father to son.

Autosomal means the mutation occurs on a chromosome other than the X or Y. Therefore, autosomal diseases affect males and females equally. Autosomal recessive means that two copies of a defective gene are required for the full-blown disease. One copy is inherited from each parent, neither of whom would normally have the disease. Autosomal dominant means one copy of a defective gene is enough to cause disease. A person who inherits the defective gene from a parent will have the disease, as will the parent.

When CMT is passed on in an autosomal dominant pattern, it can be easy to recognize in the family tree. In contrast, X-linked or autosomal recessive types of CMT might seem to occur “out of the blue.” But in reality, the mother or both parents might be carriers who silently harbor a genetic mutation. Many parents have no idea they’re carriers of a disease until they have a child with the disease.

CMT also can occur when a new mutation occurs during the child’s conception. These are called spontaneous mutations, and after they occur, they can be passed on to the next generation.

Your risk of inheriting or passing on CMT depends largely on what type of CMT you have (see “What are the different types of CMT?”) A good way to find out more about this risk is to talk to your MDA clinic physician or a genetic counselor at the MDA clinic. Also, see MDA’s pamphlet “Facts About Genetics and Neuromuscular Diseases.”

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