A 2-year-old boy presented with the complaint of swellings over the arms, patellar areas, and feet. A firm, immobile, nonerythematous swelling was first noticed on the left arm 2 months previously, and then similar lesions appeared on the other arm and knees. Arm motion was limited in the morning. Parents were unrelated and their three other children were healthy. There were no similar cases in the family.
Physical examination revealed a well-developed boy, 85 cm in height, and 13.4 kg in weight, with a firm, slightly movable nodule measuring 1.5×1.5 cm on the lateral side of the right forearm. Similar subcutaneous nodules were also found on the right arm, knees, left thigh, and ankle. The physical findings of the other systems were unremarkable.
Laboratory investigations showed the following: hemoglobin, 11 g/dL; white blood cells, 8.1×109/L; erythrocyte sedimentation rate, 4 mm/h. Tests for antistreptolysin O, C-reactive protein, and rheumatoid