HLA antigens in ankylosing spondylitis with peripheral arthritis.

was limited to children with an erosive peripheral arthritis in addition to ankylosing spondilitis. Although we did not ascertain the extent of erosive disease in all our patients, they were biased towards those with more severe disease and hence were also likely to be erosive. The inclusion of patients that had already had joint replacement helps support this conclusion. Another similarity was the occurrence of patients with childhood onset disease in both studies. Five of 25 patients from Spain had an onset below the age of 17, whereas none of the group with ankylosing spondylitis only did so, though the mean age of both