CMT1X is the second most common form of CMT, accounting for 10-16 percent of all cases. It is found on the X chromosome, one of the sex chromosomes. The flaw is caused by a gap junction beta 1 protein connected to Connexin 32. Typically, this form has onset in childhood or adolescence and often affects males more severely than females. An affected male with CMT1X cannot pass the defect to his son, but will pass it to all his daughters. An affected female has a 50 percent chance of passing the mutation to either her sons or her daughters.

Dr. Rudolph Martini at the University of Würzburg, Germany recently published work to show that the biologic factor CSF-1 is an essential mediator of Schwann cell dysfunction in mice with defective Connexin 32. With CMTA support, he is currently investigating a pharmacological approach to regulate Connexin 32 activity via this pathway in vivo. This would represent a novel type of treatment for CMT1X, as it seeks to improve peripheral nerve function by modifying an inflammatory response that he has now shown to be associated with both CMT1X and with CMT1B.