Charcot-Marie-Tooth disease (CMT) is the name given to a group of serious genetic disorders that cause defects in the nerves responsible for movement and sensation.

Over a hundred genetic mutations have been linked to CMT. These mutations lead to the degeneration of either the nerve fibers themselves or the protein coat that protects them.

As the disease progresses, the nerves lose the ability to transmit signals to and from the brain. This causes muscular atrophy and weakness in the arms, hands, legs, and feet. Patients may also lose sensation in their extremities.

The earliest symptoms of CMT are often clumsiness or muscle weakness. Patients may have difficulty walking because of “foot-drop” — an inability to keep the toes up when taking a step.

There are a number of tests that can be used to diagnose CMT but the most certain method is a genetic test for the known disease-causing mutations.

How is the test performed?

Patients will have a small blood sample drawn at a hospital or clinic. Their physician will send the blood for genetic testing and patients will get their results a few weeks later. The patients and caregivers will meet with their care team and a genetic counselor to discuss the results.

Types of genetic testing

The test can be in the form of genetic sequencing where the DNA sequence of a whole gene is determined, along with any mutations. This method is slow and time-consuming, as it must be done one gene at a time. It can also be expensive.

An alternative is next-generation sequencing, a newer type of sequencing, which makes it possible to sequence many genes in parallel.

Another testing method is called microarray. It uses a chip that contains complementary DNA sequences to many genes and mutations; microarrays allow the detection of known mutations, but might not detect new ones.

Patients should talk with their neurologists and genetic counselors to decide what type of genetic test is right for them. To find a genetic counselor in the United States and Canada, patients can search on the National Society of Genetic Counselors website.

Other information

Not everyone wants or needs to have a genetic diagnosis of CMT. For someone who has not been diagnosed with CMT, getting a positive genetic test could mean that person may no longer be eligible for supplemental insurances, such as long-term care, disability, or life insurance. It is important to consider the long-term implications of a genetic test before deciding to be tested.

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Charcot-Marie-Tooth News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.