HLA-B40: a marker for susceptibility to lung disease in rheumatoid arthritis.

We have compared the frequency of HLA antigens in groups of patients with rheumatoid arthritis (RA) who had pulmonary manifestations, other extra-articular features or articular disease alone. There was a significantly increased frequency of the antigen HLA-B40 in patients with lung involvement compared to other forms of extra-articular RA (relative risk 40.54), and when compared to the total RA group (relative risk 4.94). In contrast there was little variation in the frequency of HLA-DR4, which was significantly increased in all patient groups. These data suggest that HLA-B40 is a marker of increased susceptibility to lung disease in patients with rheumatoid arthritis.