Charcot-Marie-Tooth (CMT) disease is a group of genetic disorders that affects movement and feeling in the limbs. The disease progresses slowly and causes damage to the peripheral nerves. These nerves control muscles and transmit sensation.

CMT can be classified in a number of ways:

  • Type I (demyelinating)—This type affects the coating of the nerve called the myelin sheath, causing nerve impulses to travel more slowly. It usually occurs in childhood or the teen years. It is the most common type of CMT.
  • Type II (axonal)—This type affects the part of the nerve called the axons. Although the speed is normal, the size or amount of impulses is less than normal. This type of CMT is less common and occurs after the teen years.
  • Type III—Also called Dejerine-Sottas disease, this is a rare, severe, early onset form of CMT. It is sometimes considered to be a subtype of CMT Type I. Symptoms may include:
    • Delayed ability to walk due to weakness of the leg muscles closest to the trunk
    • Severe sensory problems
    • Hearing loss
  • Type IV (demyelinating autosomal recessive)—This is similar to Type I, but often less severe. It is less likely to be inherited by an affected individual's children.

CMT is caused by defects in specific genes.

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