HLA antigens have been identified in patients with juvenile chronic polyarthritis (J.C.P.) (n = 35). In J.C.P. the incidence of antigen B27 (57%) was found to be higher than in a normal population (n = 1,000). On recent evaluation of the clinical status, serology and x‐rays, the patients with juvenile chronic polyarthritis who have been followed up for many years, could be subdivided into four groups: Group 1: J.C.P. evolving to ankylosing spondylitis (n = 3); Group 2: J.C.P. with sacroiliitis (n = 17); Group 3: J.C.P. without sacroiliitis (n = 9); Group 4: juvenile rheumatoid arthritis characterised by a positive serology (n = 6). Groups 1 and 2 were characterised by a high incidence of antigen B27 (19/20). Only one subject of groups 3 and 4 had antigen B27. Sex distribution in groups 1 and 2 was found to be similar to that found in ankylosing spondylitis in adults and sex distribution in groups 3 and 4 was found to be similar to that found in rheumatoid arthritis in adults. It is concluded that if B27 positives develop juvenile chronic polyarthritis they have a high risk of developing sacroiliitis and acute uveitis. The authors propose to give the name Still's disease to the total group of children presenting initial symptoms corresponding to the criteria of Ansell & By waters (1959). Follow‐up of the cases permitted their further classification as juvenile ankylosing spondylitis, as juvenile chronic polyarthritis with or without sacroiliitis or as juvenile rheumatoid arthritis.

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