The most common form of the disease, Charcot–Marie–Tooth type 1A (CMT1A), originates in the duplication of the peripheral myelin protein (PMP22) gene located in chromosome 17p11.2, which results in overexpression of PMP22, a key component of the myelin sheath produced by Schwann cells. This evidence concerns the gene PMP22 and Charcot-Marie-Tooth disease type 1A.