Immunogenetic differencies between patients with familial and non-familialrheumatoid arthritis

Objective-To search for possible immunogenetic differencies between the pat ients with familial and non-familial rheumatoid arthritis (RA). Methods-The study compared 129 familial RA patients with 217 non-familial p atients for the frequencies of HLA-DR antigens including DR4 subtypes, DR4- DQB1*0301 and DR4-DQB1*0302 haplotypes and HLA-B27 antigen as well as the a ge of disease onset and existence of rheumatoid factor or joint erosions. Results-Two major differences between familial and non-familial groups were found: firstly, familial RA patients had increased frequency of HLA-DR4 as compared with the non-familial RA group (68.2 v 54.8%; p = 0.019). Secondl y, the mean age at onset of RA was significantly lower in the familial than in the sporadic RA patients (42.0 v 46.5 years; p = 0.0020) and the differ ence still remained when the DR4 positive and negative subgroups were compa red separately. Conclusion-These results confirm the more prominent association with HLA-DR 4 in familial than in the non-familial cases and suggest that accumulation of HLA risk genes may, at least partly, explain the familial occurrence of the disease. Other susceptibility genes may also be concentrated in multipl ex case families as suggested by an earlier age at the onset of RA in both HLA-DR4 positive and negative familial patients.