Because of the concurrence, in members of one family, of different autoimmune disorders [rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), psoriasis (PS), and inflammatory bowel disease (IBD)], we investigated the genotypes of each member and compared the results with current knowledge of genetic inheritance of rheumatic and other autoimmune diseases.
Sera and peripheral blood lymphocytes of 16 family members were collected for HLA typing and investigation.
All patients with RA were DR4 positive ad 4 of 5 showed the maternal A2B51DR4 haplotype. Two of 3 siblings with the genotype HLA-A2/3, B8/35, DR2/3 had SLE. Patients with IBD and psoriasis shared the haplotype HLA-A3, B35 CW4 DR2.
The results show that the important role of patients, sex and confirm the association between HLA haplotype and RA or SLE. They support the hypothesis that autoimmunity is a mendelian dominant trait, and that secondary genes, including these of the major histocompatibility complex, confer phenotypic specificity.