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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 Po 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. |
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