Differences between female and male patients with familial rheumatoid arthritis

Objective-To determine whether there are genetic differences between female and male patients with familial rheumatoid arthritis (RA). Methods-45 men and 119 women from 78 families with RA who all had at least one first degree relative with RA were compared. HLA-DRB1 alleles were anal ysed, including DRB1*04 subtypes and associations of DRB1*04 haplotypes wit h DQB1*0301 or DQB1*0302 alleles, the age of the patients at disease onset, the presence of rheumatoid factor (RF), joint erosions, and rheumatoid nod ules. Results-HLA-DRB1*13 allele (the subtype allele of DR6, reported to be prote ctive against the development of RA) was found in 14/119 (12%) of female bu t in none of the male patients (p=0.036). The HLA-DR4 allele was found slig htly more often in men than women patients with familial RA (31/45 (69%) v 75/119 (63%), NS). Men were also more often RF positive than women (44/45 ( 98%) v 98/117 (84%); p=0.031). On the other hand, the mean age at onset of RA was significantly lower in the female group (40.4 years) than in men (46 .6 years, p=0.0044). Conclusion-The results indicate that there is stronger genetic background i n familial male than female patients with RA in the genetic susceptibility defined by the studied HLA antigens. However, the earlier age of onset of t he disease in female group and the increased proportion of women with RA in dicate that there are additional sex related predisposing factors enhanced in familial cases.