LINKAGE OF A LOCUS (CMT4A) FOR AUTOSOMAL RECESSIVE CHARCOT-MARIE-TOOTH DISEASE TO CHROMOSOME-8Q

Autosomal recessive Charcot - Marie - Tooth (CMT) disease (CMT4) is a complex group of severe childhood motor and sensory neuropathies, characterized by an early age of onset with rapidly progressive distal limb weakness and atrophy. One subgroup designated CMT4 type A (CMT4A) was selected from a series of Tunisian CMT4 families according to the following electrophysiological and pathological criteria: slow motor nerve conduction velocity (MCV), severe hypomyelination upon nerve biopsy with basal lamina onion bulbs and no myelin outfolding. In an attempt to localize the CMT4A locus, we studied four inbred families with 13 affected patients. Significant evidence for linkage was found for several markers from chromosome 8q13 - 21.1 (D8S279, D8S164, D8S286, D8S84, D8S275 and D8S167). An overall two point peak lod score of z(theta)=9.19 at theta=0.00 (95% confidence limit 0.00 - 0.08) was obtained for D8S164. No evidence of genetic heterogeneity was found. The chromosomal localization of one form of CMT4 will have important implications in clarifying the nosology of this complex group of disorders.