Acute rheumatic fever and erythema marginatum in an adult patient.

A 41-year-old woman presented for evaluation of a pruritic eruption with an abrupt onset, starting on her flanks and then spreading to her arms and legs. She had 2 weeks of fever, chills, malaise, migratory joint pain, nausea, and mental confusion. An antistreptolysin O titer was positive. Upon hospital admission, bilateral lower-extremity chorea movements were observed, and her C-reactive protein level was elevated (3.7 mg/dL). Biopsy results supported erythema marginatum. Based on these clinical and laboratory findings, the diagnosis of acute rheumatic fever was established.