Sacroiliitis in juvenile chronic arthritis. A 10-year follow-up

66 children with early juvenile chronic arthritis underwent HLA A and B typing in 1974; 16 carried HLA B27. Ten of these had a pauciarticular onset, 3 systemic and 3 poly-articular. At follow-up 10 years later bilateral sacroiliitis had developed in 9 of the 16 B27 positive children, all of whom had a pauciarticular onset. Males predominated and these children had an older age of onset and a predominantly lower limb arthropathy. Enthesopathy and acute iritis further distinguished this group clinically. Other sacroiliac changes, usually simple fusion associated with severe hip involvement, were seen in 7 of the patients, 6 were girls and 6 were HLA B27 negative. Back pain and limitation had developed in 5 children, 4 of whom were B27 positive, after an average of 8 years' disease and at a mean age of 17.3 years. It is concluded that the presence of HLA B27 in boys aged 9 or over, with an onset of pauciarticular disease, signifies that they belong to the spondylitic group.