PMP22 and Charcot-Marie-Tooth disease type 4C: This symptom is not specific and thus cannot distinguish CMT4C from the other forms of demyelinating CMT, such as CMT1A, 1B, and X1, caused by mutations in PMP22, P0, or GJB1. Although cranial nerve involvement is commonly observed in CMT4C patients, we surprisingly did not detect any other cranial nerve involvement.