Coexisting rheumatoid arthritis and ankylosing spondylitis.

Since the second publication by some of the present authors in which 10 patients with coexisting rheumatoid arthritis (RA) and ankylosing spondylitis (AS) were described, 7 new cases have been found. For accuracy, all cases of the original study still available were reexamined. Of the total of 17 cases, 13 were male and 4 female. All had positive tests for rheumatoid factor and 6 had subcutaneous nodules. The male predominance and the frequency of nodules are consistent with other publications. In addition, our study demonstrates the strong association of each of these 2 diseases with its genetic marker: the antigen HLA-DR4 was present in 8 of 12 cases tested and the antigen HLA-B27 was present in 16 of the 17 cases. The coexistence of these 2 classical rheumatological entities in the same patient appears to occur by chance and is probably often overlooked.