Charcot-Marie-Tooth neuropathies: from clinical description to molecular genetics

Ninety-five families with Charcot-Marie-Tooth (CMT) neuropathies were studied clinically, electrophysiologically (MNCVs and EMGs), and by molecular genetics. Fifty-four families (56.8%) were type 1A mapped at 17p11.2-p12 and DNA duplication was present in 50 (92.6% of CMT1A families). One family with type 1B (1.1%) mapped at 1q22-q23 showed a point mutation of the myelin P0 gene. Eighteen families (18.9%) were type CMT2 based on electrophysiological studies. Molecular genetics was not yet conclusive. Twenty CMT families were with X-linked dominant inheritance (CMTX1) (21.1%) mapped at Xq13.1 and connexin 32 (CX32) point mutations were present in 15 families (75%) (five nonsense mutations, eight missense mutations, two deletions). Two CMT families (2.1%) with X-linked recessive inheritance showed no point mutations of CX32 and their mapping was different from CMTX1, respectively at Xp22.2 for CMTX2 and at Xq26 for CMTX3.