Sharing of HLA haplotype by parents of patients with systemic lupus erythematosus.

Forty-four families were studied for the relationships between HLA and systemic lupus erythematosus (SLE). Nine families had more than 1 member with SLE; haplotype sharing between SLE patients within a family was no greater than expected by chance. Fourteen of 236 relatives had antinuclear antibodies (ANA); the frequency of haplotype sharing between SLE patients and ANA-positive relatives was no greater than expected by chance. One HLA-A,B haplotype was shared by 7 of 35 parent pairs, a frequency (20%) significantly greater (P = 0.004) than in 2 groups of normal controls (3.1% and 5%). These data provide evidence for HLA-linked genes operating recessively in the expression of SLE.