Localization of the Schwartz-Jampel syndrome (SJS) locus to chromosome 1p34-p36.1 by homozygosity mapping.

Schwartz-Jampel syndrome (SJS, MIM 255800), also known as chondrodystrophic myotonia, is a rare autosomal recessive disorder characterized by generalized myotonia, skeletal abnormalities and facial dysmorphism. Using homozygosity mapping, we localized the SJS locus to chromosome 1p34-p36.1 in a 8 cM interval flanked by markers D1S199 and D1S234. Families of different ethnic backgrounds (Tunisia and South Africa) showed genetic linkage to the same locus. Moreover, one Algerian family also demonstrated evidence of genetic linkage to 1p34-p36.1. Taken altogether, our results suggest genetic homogeneity, at least in the group of families analyzed.