Positive serology for Lyme borreliosis in patients with juvenile rheumatoid arthritis in a Lyme borreliosis endemic area: analysis by immunoblot.

Juvenile rheumatoid arthritis (JRA) and the arthritis of Lyme borreliosis in children can mimic each other. As false positive reactions are frequent in ELISA for Lyme borreliosis, they cannot be used reliably to make the distinction. Ninety-nine children diagnosed as having JRA at a children's hospital in an endemic area were evaluated by ELISA and immunoblot for antibodies to Borrelia burgdorferi. Sera from 9% were positive by ELISA, 5 of which showed bands on immunoblot. None met criteria for positive immunoblot. The antigenic basis of false positive ELISA was most frequently a reactivity to both 21 and 41 kDa. Analysis by immunoblot can help to definitively exclude Lyme borreliosis in children presenting with JRA in an endemic area.