Sharing of MHC haplotypes among patients with systemic lupus erythematosus from unrelated Caucasian multicase families: disease association with the extended haplotype [HLA-B8, SC01, DR17].

OBJECTIVE: Systemic lupus erythematosus (SLE) is an autoimmune rheumatic disease often clustered in families. We investigated the association between MHC haplotypes and SLE in multicase Caucasian families.
METHODS: Ten consecutive families with 2 or more patients with SLE, in total 27 patients among 66 individuals, were studied. MHC haplotypes were determined by typing for HLA-A, B, C, DR, and DQ by serological and DNA methods. Complotypes were determined by protein typing and C4 gene polymorphism by DNA analysis.
RESULTS: Fifty-four independent MHC haplotypes were found. Ten of the 31 haplotypes in the patients with SLE were examples of the extended haplotype [HLA-B8,SC01,DR17]. Six of these were found in 2 or more patients with SLE within the same family. All the 14 SLE sib-pairs in the families shared at least one haplotype and in 9 of the sib-pairs the shared haplotype was [HLA-B8,SCO1,DR17]. Three SLE associated haplotypes were [HLA-B7,SC31,DR15]. Four of the 27 patients with SLE were C4A deficient. Two C2 deficient siblings were homozygous for the haplotype [HLA-B18,S042,DR15].
CONCLUSION: We demonstrate that a very limited number of MHC haplotypes are associated with familial SLE. The haplotype [HLA-B8,SCO1,DR17] was closely related with the disease. There was no evidence suggesting familial SLE constitutes a disease subset. Determination of MHC haplotypes in multicase families is of value for assessment of disease susceptibility.