Compound heterozygosity for a point mutation and a deletion located at splice acceptor sites in the LAMB3 gene leads to generalized atrophic benign epidermolysis bullosa

An autosomal recessive disorder, generalized atrophic benign epidermolysis bullosa, is a rare form of nonlethal type junctional epidermolysis bullosa. It is associated not only with skin fragility but also with other unique clinical features including widespread atrophic skin changes, alopecia, reduced axillary and pubic hair, dysplastic teeth, and dystrophic nails. The majority of generalized atrophic benign epidermolysis bullosa cases are caused by mutations in the COL17A1 gene coding for type XVII collagen (or the 180 kDa bullous pemphigoid antigen). Another candidate gene for mutations in some forms of generalized atrophic benign epidermolysis bullosa is LAMB3 encoding the β3 chain of laminin 5. This report documents compound heterozygosity for novel mutations in LAMB3 of a Japanese patient showing typical clinical features of generalized atrophic benign epidermolysis bullosa. One is an A-to-G transversion at the splice acceptor site of intron 14, which is designated as a 1977-2A→G mutation; the other is a deletion of 94 bp located at the junction of intron 18 and exon 19, which is a 2702-29del94 mutation. Reverse transcriptase polymerase chain reaction analysis suggested skipping of exon 19 in LAMB3 mRNA produced from the allele with 2702-29del94 and impaired stability of the aberrant mRNA transcribed from the second allele with the 1977-2A→G mutation.