A 10-year-old boy with fever arthritis and a painful rash

摘要

A 10-year-old previously healthy, fully immunized boy presented to hospital with a 10-day history of daily fevers, multiple painful, swollen joints, and a painful, purple rash. He had no sick contacts or recent travel and there was no family history of autoimmune disease. A week prior to symptom onset, he had an episode of sore throat which was treated with a course of cefprozil, but no throat culture was performed. He was not on any other medications. On physical exam, he was febrile at 39C, but vital signs were otherwise normal. He had polyarthritis involving bilateral elbows, wrists, ankles, and knees, a tender violaceous, nodular rash on his right lower leg (Figure 1), and, two smaller nodular lesions on his forearms bilaterally (Figure 2). His exam was otherwise normal. Laboratory investigations revealed an elevated white blood cell of 16.5 × 109/L, anemia with hemoglobin 104 g/L and normal platelets of 352 × 109/L. Inflammatory markers were elevated with C-reactive protein 107.9 mg/L and erythrocyte sedimentation rate (ESR) 80 mm/h. Urinalysis, liver function, renal function, creatine phosphokinase, viral serologies, C3/C4, immunoglobulins, and autoantibodies (antinuclear antibodies [ANA] and antineutrophil cytoplasmic antibody [ANCA]) were normal. Throat culture was negative, but anti-streptolysin O titer (ASOT) was elevated at 1,600 IU/mL. A full thickness biopsy of his rash was consistent with the suspected diagnosis.