Two new loci for autosomal recessive ichthyosis on chromosomes 3p21 and 19p12-q12 and evidence for further genetic heterogeneity

Autosomal recessive ichthyosis (ARI) includes a heterogeneous group of diso rders of keratinization characterized by desquamation over the whole body. Two forms largely limited to the skin have been defined: lamellar ichthyosi s (LI) and nonbullous congenital ichthyosiform erythroderma (NCIE). A first gene for LI, transglutaminase TGM1, has been identified on chromosome 14, and a second one has been localized on chromosome 2. In a genomewide scan o f nine large consanguineous families, using homozygosity mapping, two new l oci for ARI were found, one for a lamellar form in a 6-cM interval on chrom osome 19 and a second for an erythrodermic form in a 7.7-cM interval on chr omosome 3. Linkage to one of the four loci could be demonstrated in more th an half of 51 consanguineous families, most of them from the Mediterranean basin. All four loci could be excluded in the others, implying further gene tic heterogeneity in this disorder. Multipoint Linkage analysis gave maxima l LOD scores of 11.25 at locus D19S566 and 8.53 at locus D3SS564.