RECESSIVE SCHWARTZ-JAMPEL SYNDROME (SJS) - CONFIRMATION OF LINKAGE TOCHROMOSOME 1P, EVIDENCE OF GENETIC HOMOGENEITY AND REDUCTION OF THE SJS LOCUS TO A 3-CM INTERVAL

Schwartz-Jampel syndrome (SJS), or chondrodystrophic myotonia, is a ra re autosomal recessive disorder characterized by generalized myotonia resulting in a particular, recognizable facies and osteoarticular abno rmalities, Some of us have recently shown genetic linkage of SJS to a locus on lp34-p36.1 in five families, Here, we show by homozygosity ma pping and segregation analysis that eight new families are most likely linked to the SJS locus on chromosome 1, confirming the localization of SJS to chromosome Ip and suggesting genetic homogeneity. Recombinat ion events reduced the SJS locus from a generic interval of 8 to 3 cM, which should facilitate the identification of the SJS gene, Low clini cal variability was observed between the studied families, except for osteoarticular abnormalities, Since the severity and the location of o steoarticular abnormalities varied from one individual to another, eve n in the same Families, other factors than the SJS gene itself, geneti c or epigenetic, might contribute to the phenotype.