ABSTRACT
The phenotypic frequencies of human major histocompatibility complex class I, II, and III antigens and immunoglobulin allotypes (Gm factors) were determined in 56 patients (55 women, 1 man) who had lupus-like disease induced by venopyronum dragées. The findings in these patients were compared with those of a control group. We found a significant increase of HLA-DR4 (57.1% versus 26.5%, relative risk [RR] 3.7) and a decrease of HLA-DR3 (3.6% versus 19.1%, RR 0.16) in the patient group. In addition, the haplotype Gm 1;21 (60.7% versus 32.9%, RR 3.2), and the phenotype Gm 1,3;5,21 (46.4% versus 25.8%, RR 2.5) were significantly increased. Both the haplotype Gm 1;21 and the phenotype Gm 1,3;5,21 are associated with HLA-DR4 in pseudolupus patients but not in controls. The coincidence of HLA-DR4 and Gm 1;21 markedly increases the risk of acquiring pseudolupus (RR 6.9). We conclude that the pathogenesis of pseudolupus is influenced by at least 2 independent genetic factors. A similar HLA association has been described in hydralazine-induced lupus, and this suggests a common pathogenic mechanism.
