Junctional epidermolysis bullosa inversa (locus EBR2A) assigned to 1q31 by linkage and association to LAMC1.

Junctional epidermolysis bullosa inversa is an autosomal recessive blistering skin disease with an ultrastructural hemidesmosome defect similar to that of the Herlitz disease, yet with a non-lethal and different course of the disease. Its delineation is based on five geographically associated Norwegian families where all parents are likely to carry a mutant EBR2A allele identical in descent. Three informative families show a lod score of +1.65 at zero recombination to a trinucleotide repeat marker in intron 20 of the laminin gamma 1 (LAMC1, previously LAMB2) locus on 1q31. The four patients of these families are all homozygous for the 146 bp LAMC1 allele present only on 5% of random Norwegian chromosomes. The daughter of a deceased patient in a fourth family carries the same 146 bp allele. This extreme association confirms that the disease locus, EBR2A, is at or closely linked to LAMC1. Localized and generalized Mitis types as well as the majority of tested families with the Herlitz type of junctional epidermolysis bullosa appeared not to be similarly linked or associated to LAMC1. The MspI and AluI RFLPs of LAMC1 showed absolute allelic association. Each of the two RFLP haplotypes showed association to either 'long' or 'short' intron 20 STR alleles.