Histocompatibility antigens in childhood-onset arthritis.

One hundred and twelve well-studied patients with a prior diagnosis of juvenile rheumatoid arthritis were differentiated into seven clinically distinct subgroups, including a group in whom recognizable ankylosing spondylitis had developed by time of follow-up. An apparent increased prevalence of HLA-B27 in the entire series (26%) was clearly related to its increased prevalence in only two subgroups: patients whose disease had progressed to overt ankylosing spondylitis (five of five patients) and boys with pauciarticular arthritis whose disease would be consistent with early ankylosing spondylitis (11 of 18 patients). There were no significant associations of B27 with systemic onset JRA, polyarticular JRA, pauciarticular JRA in girls, or JRA with chronic iridocyclitis. The only other significant alterations found were increased prevalences of HLA-A2 and HLA-BW15 in patients with polyarticular disease without identifiable rheumatoid factor. This study emphasizes that the clinical disorders included under the category of juvenile rheumatoid arthritis represent more than a single disease and that this heterogeneity must be considered in interpreting studies such as those of histocompatibility typing.