|CMT causes degeneration of the peripheral nerves, leading to muscle weakness in the body’s extremities.|
Charcot-Marie-Tooth disease (CMT) is a neurological disorder named after the three physicians who first described it in 1886 — Jean-Martin Charcot and Pierre Marie of France, and Howard Henry Tooth of the United Kingdom.
CMT causes damage to the peripheral nerves, which carry signals from the brain and spinal cord to the muscles, and relay sensations, such as pain and touch, to the brain and spinal cord from the rest of the body. There are a number of types of CMT.
CMT causes muscle weakness and atrophy, and some loss of sensation in the feet, the lower legs, the hands and the forearms. It also often causes contractures (stiffened joints due to abnormal tightening of muscles and associated tissues), and sometimes, curvature of the spine (scoliosis).
At the severe end of the CMT spectrum, the disease can affect nerves other than those that go to and from the extremities. If the nerves that go to and from the diaphragm or intercostal (between the ribs) muscles are affected, respiratory impairment can result. For more, see Signs and Symptoms.
CMT is caused by defects in the genes for proteins that affect axons — fibers that carry electrical signals between the brain and spinal cord and the rest of the body — or in the genes for proteins that affect myelin, a coating on axons that insulates and nourishes them.
More than 30 genes have been implicated in CMT, each one linked to a specific type (and in many cases, more than one type) of the disease.
CMT can be inherited in several ways: autosomal dominant (through a faulty gene contributed by either parent); autosomal recessive (through a faulty gene contributed by each parent); or X-linked (through a gene on the X chromosome contributed by either parent.) For more on causes and inheritance patterns in CMT, see Causes/Inheritance.
Depending on the type of CMT, onset can be from birth to adulthood, and progression is generally slow. CMT usually isn't life-threatening, and it almost never affects the brain.
CMT research is focused on exploring the effects of defects in genes related to the peripheral nervous system and devising strategies to combat these effects.