Erythema Marginatum In A Case Of Post-Streptococcal Arthralgia: A Rash Mimicking Urticaria

Erythema marginatum secondary to streptococcal infection is classically associated with acute rheumatic fever and fulfills one of the Jones criteria for this diagnosis. We describe a case of streptococcal associated erythema marginatum without rheumatic heart disease in a 12 year old male with post streptococcal arthralgia and myalgia. The rash was originally suggestive of urticaria. He was initially seen with a five week history of fever. Examination and laboratory evaluation did not yield an acute infectious etiology for his fever. However anti-streptolysin O and anti-deoxyribonuclease B were very elevated. Historically, he had a sore throat 3 weeks prior to his presentation and had been treated by his PCP with amoxicillin; no cultures were done. Based on this history and his elevated anti-streptococcal antibody titers, he was started on cefadroxil and non-steroidal antiinflammatory drugs. Several days after antibiotics were started and several weeks after his fever and arthralgia symptoms had begun, he developed a trunk and upper arm rash with raised, erythematous borders. Dermatology diagnosed it as urticaria and cetirizine was recommended. The antibiotic was switched to azithromycin but the rash persisted. He was referred to rheumatology who diagnosed a post-streptococcal syndrome. He was started on penicillin under close observation and no changes in the rash were noted. His aches improved in a matter of days. Dermatology biopsied his rash and the histopathology was consistent with both urticaria and published reports of erythema marginatum. Electrocardiogram and serial echocardiographs were normal. His anti-streptococcal titers returned to near normal in 12 months. His elevated inflammatory markers normalized. This case demonstrates a post-streptococcal syndrome with a rash suggestive of urticaria, but was later confirmed to be erythema marginatum in the absence of carditis. Confirming the diagnosis of erythema marginatum was critical, since it enabled a diagnosis of rheumatic fever which had direct implications for prophylactic treatment.