Molecular basis of non-lethal junctional epidermolysis bullosa: identification of a 38 basepair insertion and a splice site mutation in exon 14 of the LAMB3 gene

Epidermolysis bullosa (EB) is a group of genodermatoses characterized by fragility and easy blistering of the skin. In the junctional forms of EB (JEB), blisters occur at the level of the lamina lucida, and specific mutations have been detected in the genes encoding different components of the hemidesmosomal-anchoring filament complex. In the non-lethal form of JEB (NL-JEB), mutations in genes encoding two of the polypeptide chains of the anchoring filament protein laminin 5 have recently been described. In this study, we searched for mutations in a family using PCR amplification of exon 14 of LAMB3, the laminin 5 beta(3) chain gene, followed by heteroduplex analysis and automated sequencing of the PCR products, We detected a novel combination of mutations in this family, consisting of an out-of frame insertion on one allele, and a splice site mutation on the other allele, representing the first report of a large insertion in LAMB3, together with a splice site mutation inherited in trans, which result in the NL-JEB phenotype.