Mimicking ST-segment elevation myocardial infarction upon presentation, acute nonrheumatic streptococcal myocarditis is a treatable etiology of myocarditis which has only been infrequently reported.

Patients were identified through a retrospective query of electronic medical records over a 17-year period (January 1994 to December 2010). We describe a case series of acute nonrheumatic streptococcal myocarditis complicating pharyngitis in young adults.

Nine patients were identified; 89% were male, patients had an average age of 28.6 years, and 56% and 22% had confirmed group A and group G streptococcus, respectively. Latency from pharyngitis to chest pain averaged 3.1±1.1 days. No patients met the revised Jones criteria for acute rheumatic fever. All 9 patients (100%) presented with ST-segment elevations on electrocardiography and elevated cardiac biomarkers. Average peak creatine kinase was 934 U/L (normal<400 U/L), creatine kinase-MB was 82 ng/mL (normal<6.9 ng/mL), and troponin T was 2.30 ng/mL (normal<0.03 ng/mL). Six patients underwent coronary angiography, which revealed no obstructive culprit lesions. Cardiac magnetic resonance imaging confirmed myocarditis in 3 patients and was used to document resolution in follow-up for 2 patients. All patients had a complete clinical recovery.

Acute nonrheumatic streptococcal myocarditis is an under-recognized and treatable cause of ST-segment elevation and chest pain in young adults with a history of recent pharyngitis. Etiopathology extends beyond Lancefield group A streptococcus and includes group G streptococcal infection. Cardiac magnetic resonance may be useful in confirming the diagnosis and documenting the resolution.