A systematic survey of the HLA B27 prevalence in inflammatory rheumatic diseases.

HLA B27 has been tested systematically in 246 patients attending a rheumatology clinic for chronic inflammatory arthritis or spondylitis. Patients were allocated to nine groups: typical ankylosing spondylitis, ankylosing spondylitis with moderate involvement without peripheral arthritis, ankylosing spondylitis with moderate involvement and with peripheral arthritis, juvenile chronic arthritis, Reiter's syndrome, Yersinia arthritis, arthropathies of inflammatory bowel disease, psoriatic arthritis, seronegative and seropositive rheumatoid arthritis. Except for seropositive rheumatoid arthritis, a significant association with HLA B27 antigen was found in all groups. In the seronegative rheumatoid arthritis group HLA B27 was present in 40% of the cases in contrast to 5.6% of the seropositive rheumatoid arthritis cases. These data confirm that a wide range of the so called "seronegative arthropathies" are associated with HLA B27 and suggest that sex and HLA B27 antigen are important factors in the manifestation of rheumatic disease. Women had less severe spondylitic changes but more peripheral arthritis of the small joints. Ankylosing spondylitis in its various forms had a comparable sex distribution despite relatively mild disease in females. The mean age of onset in the HLA B27 associated diseases was found to be significantly lower than in the seropositive rheumatoid arthritis group.