Pemphigus vulgaris in distant relatives of two families: association with major histocompatibility complex class II genes.

We describe major histocompatibility complex (MHC) class II gene haplotypes in two extended families, each of which has two members with pemphigus vulgaris (PV). One family is of Ashkenazi Jewish descent and the other family of English-Scottish descent. In one family the patients are distant relatives; in the other, both share the same mother but have different fathers. The affected relatives in the two families have never shared a common environment and live in distant states. All four PV patients, regardless of whether they were of Ashkenazi Jewish or of English-Scottish descent, had the same haplotype, namely HLA-DRB1 0402, DQA1 0301, DQB1 0302. Thus the PV patients, even though distantly related within a family, had the same MHC class II haplotype previously documented in Jewish patients. This observation further supports the concept that PV may result from an enhanced genetic susceptibility or predisposition to the disease.