Autosomal dominant distal spinal muscular atrophy type V (dSMA-V) and Charcot-Marie-Tooth disease type 2D (CMT2D) segregate within a single large kindred and map to a refined region on chromosome 7p15

Two separate disorders, autosomal dominant distal spinal muscular atrophy type V (dSMA-V) characterized by marked bilateral weakness in the hands and atrophy of thenar eminence and the first interosseous muscle, and Charcot-Marie-Tooth disease type 2D (CMT2D) characterized by sensory deficits in addition to the upper limb weakness and wasting, have been independently linked to chromosome 7p. We identified a multigenerational Mongolian kindred with 17 members affected with either dSMA-V or CMT2D and mapped both syndromes to the same region on chromosome 7p15. A maximum two-point lod score of 4.74 at recombination fraction zero was obtained with marker D7S474. Tight linkage without recombination was also detected with markers D7S526 and D7S632. A multipoint lod score of 6.07 suggested that the gene is located between markers D7S526 and D7S474. A single conserved haplotype was associated with dSMA-V and CMT2D. Based on informative recombination events, the disease locus was placed between markers D7S516 and D7S1514 within the 7p15 band. Data obtained from this study suggest that a single gene is responsible for both syndromes, dSMA-V and CMT2D, and extend our knowledge of the candidate region.