[The genetics of type 1 Charcot-Marie-Tooth disease, the hereditary focal neuropathies and the hereditary distal motor neuropathies]

Charcot-Marie-Tooth disease (CMTD) or hereditary motor and sensory neuropathy shows great genetic heterogeneity. The type 1 (CMT-1) or demyelinating form and the type 2 (CMT-2) or neuronal form are two clinically and genetically distinct forms. Apart from the above mentioned motor and sensory forms, there is another type of neuropathy in which the clinical and neurophysiological involvement is exclusively motor and is known as distal spinal atrophy or hereditary distal motor neuropathy (HDMN), which is a syndrome to be included among the CMTD. The CMT-1 is the most prevalent form and the best understood from the genetic point of view. At least four genes have been reported to be involved: the gene for 22 kDa peripheral myelin protein (PMP-22), situated on the 17p11.2 chromosome (locus CMT-1A); the gene for myelin 0 protein situated on chromosome 1q23 (locus CMT-1B); the gene for conexine 32 (Cx32), found on chromosome Xq13 (locus CMT-X) and the gene EGR2 found on chromosome 10q21.1-...