An African American boy aged 7 years presented with right ankle pain, overlying soft tissue erythema, and swelling. He was diagnosed with cellulitis and prescribed 10 days of sulfamethoxazole and trimethoprim. Although his right ankle pain and swelling initially improved, he presented 1 week later with left ankle and right knee pain and swelling. He had a tender, nonerythematous, subcutaneous 1-cm nodule above the right olecranon. Laboratory results were notable for an elevated erythrocyte sedimentation rate of 44 mm/h, a C-reactive protein level of 0.84 mg/L (to convert to nanomoles per liter, multiply by 9.524), an antistreptolysin O titer of 1150 IU/mL, and an anti-DNase B titer of 961 U/mL. The results of the rapid strep test and throat culture were normal, but given his constellation of symptoms, he was diagnosed with acute rheumatic fever. Echocardiogram and electrocardiogram were normal, and he was treated with amoxicillin. Four days after discharge, he developed new painful skin lesions on his elbows, forearms, and legs. He remained afebrile but continued to complain of persistent left ankle and right knee pain.
Warren JT, Miller CP, White AJ. 7-Year-Old With a Painful Rash. JAMA Pediatr. 2016;170(8):801-802. doi:10.1001/jamapediatrics.2015.4563