IgA deficiency in juvenile chronic polyarthritis.

Immunoglobulins measured sequentially in 582 juvenile chronic polyarthritis patients revealed 12 with persistently absent IgA and 15 consistently below 20 mg/dl. There was an increased presentation with pauciarticular onset but systemic disease was the same as in the whole group. Follow-up showed that 9 of the 12 without IgA developed polyarthritis as have 11 of the 15 with low IgA; in contrast to previous studies, the disease has been severe in at least half of the patients.