CMTX1 is caused by X-Linked dominant mutations in the GJB1 gene. CMTX1 is the second most common type of CMT, comprising approximately 16%of all CMT cases. Because the GJB1 gene lives on the X chromosome, this is an X-Linked CMT.

CMTX1 symptom onset can occur anywhere from infancy to young adulthood. CMTers who have CMTX1 usually experience gait disturbances, lower and upper limb weakness and sensory loss, hand tremors, frequent ankle sprains, “toe-walking,” and foot-drop and an early age. CMTX1 demonstrates both demyelinating and axonal neuropathy properties. Developmental delays and sensorineural hearing loss have been reported in CMTX1.

A trait that sets all X-Linked CMT apart from the other types of CMT is that there can be no male-to-male transmission. Also, males who have X-Linked CMT tend to be more severely affected than females who have X-Linked CMT.