ALLELIC HETEROGENEITY IN HEREDITARY MOTOR AND SENSORY NEUROPATHY TYPE-IA (CHARCOT-MARIE-TOOTH DISEASE TYPE-1A)

The most frequently found mutation in autosomal dominant hereditary mo tor and sensory neuropathy type I (HMSN I) is a large duplication on c hromosome 17p11.2 containing probes VAW409R3, VAW412R3, and EW401. We investigated a family with severe features of HMSN I, and demonstrated the absence of this duplication by a quantitative analysis of the hyb ridization signals of VAW409R3 and VAW412R3. Linkage analysis, however , revealed linkage with probe VAW409R3a (lod score, 3.22), which demon strates the existence of allelic heterogeneity within the HMSN Ia locu s. These findings have implications for clinical practice and for inve stigating the identity of the HMSN Ia gene.