CMT4 is a subtype of CMT, a genetic, neurological disorder that causes damage to the peripheral nerves — tracts of nerve cell fibers that connect the brain and spinal cord to muscles and sensory organs.
CMT4 causes weakness, usually mostly distal (far from the center of the body) but sometimes involving proximal (near the center of the body) muscles. Impairment or changes in sensations (such as the sense of touch or ability to perceive temperature changes) also can occur. When CMT4 begins in infancy, it’s characterized by low muscle tone. See Signs and Symptoms  for more.
CMT4 is caused by defects in the genes that affect myelin, a coating that insulates and nourishes axons (fibers that carry electrical signals between the brain and spinal cord and the rest of the body).
CMT4 is inherited in an autosomal recessive pattern. For more, see Causes/Inheritance .
CMT4 has its onset in infancy, childhood or adolescence, and progression is generally slow. Young children with CMT4 can have delayed motor (movement-related) development.
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.