Carditis associated with Mycoplasma pneumoniae infection.

A 16-year-old boy with acute perimyocarditis had serological evidence of Mycoplasma pneumoniae infection. The endomyocardial biopsy specimen showed grade 2 active lymphocytic myocarditis. A T-cell study suggested a cell-mediated immune process in the pathogenesis of carditis. Mycoplasma pneumoniae needs to be considered as a possible cause of acute carditis, and histological findings may influence management.