CMT is an inherited neurological disease characterized by the gradual degeneration of nerves which starts in the hands and feet and results in progressive numbness, muscle weakness and loss of function. Type X1 is an inherited defect of the X chromosome (defect in GJB1 gene) and affects males to a greater degree than females. Transient central nervous system symptoms are also sometimes involved. See also Charcot-Marie-Tooth disease, X-linked, 1