What do we know about Charcot-Marie-Tooth disease

Charcot-Marie-Tooth disease (CMT) is an inherited neurological disease characterized by a slowly progressive degeneration of the muscles in the foot, lower leg, hand, and forearm, and a mild loss of sensation in the limbs, fingers, and toes. The first sign of CMT is generally a high arched foot or gait disturbances.

Other symptoms of the disorder may include foot-bone abnormalities such as high arches and hammer toes, problems with hand function and balance, occasional lower leg and forearm muscle cramping, loss of some normal reflexes, occasional partial sight and/or hearing loss, and, in some individuals, scoliosis (curvature of the spine).

People with CMT disease usually begin to experience symptoms in adolescence or early adulthood. There is no cure for the disease, but there are treatment options, including physical therapy and bracing. Life expectancy is usually normal.

CMT disease can be divided into two classes, depending on where the dysfunction occurs in the peripheral nerves:

* In CMT type 1, the peripheral nerves' axons - the part of the nerve cell that transmits electrical signals to the muscles - lose their protective outer coverings, their myelin sheaths. This disrupts the axons' function.

* In CMT type 2, the axons' responses are diminished due to a defect within the axons themselves. CMT type 2, the less common of the two classes, can be further separated into at least six subtypes, caused by defects in different genes.