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 4X is an inherited defect of the X chromosome and affects males to a greater degree than females and also involves mental retardation and deafness.
* Deafness * Mental retardation * Muscle weakness in extremities * Reduced nerve conduction speed * Wasted muscles in extremities
Hereditary neuropathies are classified by Mendelian Inheritance in Man (MIM). Charcot-Marie-Tooth Disorders: Genetic and Clinical Feature Comparison
The disease phenotype in family 1 was characterized by infantile onset, weakness of lower legs, areflexia, pes cavus, and mental retardation (2 of 5 patients). The disease phenotype in families 2 and 3 was characterized by late onset, distal weakness, and normal intelligence. Hereditary spastic paraparesis was also present in the CMT patients of family 2. Thirty X-linked DNA markers were used for linkage studies.