[Juvenile ankylosing spondylitis (JAS) and juvenile rheumatoid arthritis (JRA)].

The diagnosis of JAS in 19 of the 24 patients with oligo-articular and the polyarticular subtypes of JRA established primarily was reexamined. Coexistence of JAS and rheumatoid arthritis was found in 4 of the 19 patients with JAS. Of the 19 patients with JAS, 18 were male and 1 was female. The mean age of onset of the disease was 12.6 years (ranging from 8 to 16). Peripheral arthritis was the first symptom in all the 19 patients, predominantly in the joints of knee, hip and ankle. 69% of the 13 patients with hip involvement developed deformity. Twelve patients had lumbosacral pain. Arthritis occurred in 7 of the 19. There was X-ray evidence of sacroilitis in all the JAS patients. In 3 of the 19 patients' families, all the family members had ankylosing spondylitis. Laboratory investigations confirmed the presence of HLA-B27 and absence of RF and ANA in these 19 patients. The study shows that early findings of JAS are not easy to distinguish from those of JRA and that the diagnosis of JAS should be considered for a boy of teenage with chronic arthritis.