PMP22 and Charcot-Marie-Tooth disease type 1A: The most common form of CMT is the type 1A (CMT1A, MIM#118220), an autosomal dominant demyelinating neuropathy caused by a duplication of the peripheral myelin protein 22 (PMP22) gene located on chromosome 17, representing about 80% of all demyelinating forms of CMT (2).