Myocarditis Following Invasive Group A Streptococcus Infection: Important Differential Diagnostic Distinctions

Nonrheumatic streptococcal pharyngitis-associated myocarditis presents as acute myocarditis within days of Group A Streptococcus pharyngitis, typically resolving with antibiotics and minimal sequelae. It is thought to result from direct bacterial toxin injury rather than autoimmunity. Little epidemiologic data regarding its incidence and prevalence exist, and standardized diagnostic criteria are lacking. In contrast, acute rheumatic fever develops 2-4 weeks after a Group A Streptococcus pharyngitis and is autoimmune-mediated. Diagnosis is based on the revised Jones criteria, and only carditis leads to sequelae, including rheumatic heart disease. We report the case of a 21-year-old male, in a high-resource setting, with invasive Group A Streptococcus who developed carditis with mitral regurgitation and heart failure, for which nonrheumatic streptococcal pharyngitis-associated myocarditis and acute rheumatic fever with carditis were considered. This case highlights the need for clinical differentiation between, and further study of, both entities.