Familial giant cell arteritis: report of an HLA-typed sibling pair and a review of the literature.

We report a brother and sister who developed biopsy-proven giant cell arteritis four years apart and summarize the eight previously well-documented families of first-degree relatives with unequivocal disease. HLA haplotypes for both siblings included DRB1*03 (DR3) and the *0401 allele of DRB1*04 (DR4). The reported association of giant cell arteritis with HLA-DR4 and its occurrence in first-degree relatives support a genetic component in its pathogenesis.