Familial giant cell arteritis and polymyalgia rheumatica: aggregation in 2 families.

The ethnic and geographic prevalence, the familial aggregation, and the reported association with some HLA class II antigens of both giant cell arteritis (GCA) and polymyalgia rheumatica (PMR) strongly suggest the role of genetic factors in the pathogenesis of these diseases. We describe the familial aggregation of GCA and PMR in 2 unrelated families from Northern Italy. In the first family, 2 sisters developed GCA a few months apart. In the second, one sister had GCA, and 2 years later her siblings developed PMR nearly simultaneously. Patients with GCA in the first family shared the whole HLA genotype (A*24,*26, B*38,*55, DRB1*11,*14, DQB1*05,*07, DRB3*). In the second family, both PMR siblings carried the A*68, B*44, DRB1*11, DQB1*07, DRB3* alleles. Thus all patients of both families shared DRB1*11, DQB1*07, and DRB3*. Predisposing immunogenetic factors of both GCA and PMR are discussed.