GENETIC HOMOGENEITY IN SJOGREN-LARSSON SYNDROME - LINKAGE TO CHROMOSOME 17P IN FAMILIES OF DIFFERENT NON-SWEDISH ETHNIC-ORIGINS

Sjogren-Larsson syndrome (SLS) is a rare, autosomal recessive disorder that is characterized by congenital ichthyosis, mental retardation, a nd spastic diplegia or tetraplegia. Three United States families, thre e Egyptian families, and one Israeli Arab family were investigated for linkage of the SLS gene to a region of chromosome 17. Pairwise and mu ltipoint linkage analysis with nine markers mapped the SLS gene to the same region of the genome as that reported in Swedish SLS pedigrees. Examination of recombinants by haplotype analysis showed that the gene lies in the region containing the markers D17S953, D17S805, D17S689, and D17S842. D17S805 is pericentromeric on 17p. Patients in two consan guineous Egyptian families were homozygous at the nine marker loci tes ted, and another patient from a third family was homozygous for eight of the nine, suggesting that within each of these families the region of chromosome 17 carrying the SLS gene is identical by descent. Linkag e of the SLS gene to chromosome 17p in families of Arabic, mixed Europ ean, Native American, and Swedish descent provides evidence for a sing le SLS locus and should prove useful for diagnosis and carrier detecti on in worldwide cases.