PMP22 and Charcot-Marie-Tooth disease: Thus, CMT variants were identified almost equally frequent in the sporadic and nonsporadic CMT families, that is, PMP22 duplication 11% (3/27) versus 15% (8/54) and point mutations 30% (8/27) versus 35% (19/54), justifying the inclusion of the 27 sporadic CMT families in our material.