Charcot-Marie-Tooth disease (CMT) is a large group of inherited peripheral neurologic disorders, meaning conditions that affect the connections between the brain and the muscles and skin. In general, CMT is characterized by the progressive loss of muscle tissue and sensation in different parts of the body, though symptoms will vary depending on the type of CMT. Symptoms classically include curled toes (claw toe), a high arched foot, loss of muscle mass in the lower leg, and increasing weakness. Symptoms of CMT typically begin in late childhood or early adulthood, but age of disease onset varies. The disease is hereditary (passed to the affected individual from one or both parents) and 1 in 2,500 individuals is affected by CMT, making it relatively common. Diagnosis of CMT is based on symptoms, nerve testing performed by a specialist, and medical tests to look for specific genetic causes. All types of CMT Type 4 are very rare. Type 4C is caused by an unknown mutation, and is characterized by child onset of CMT symptoms and early scoliosis (developing an abnormal curvature of the spine).