Eosinophilic myocarditis associated with toxicodermia caused by phenobarbital

We report on a 37-year-old man with congestive heart failure caused by eosinophilic myocarditis associated with toxicodermia. He developed many annular skin eruptions and peripheral eosinophilia due to reactions against phenobarbital. Right ventricular endomyocardial biopsy revealed extensive infiltration of eosinophils in the myocardium. A drug lymphocyte-stimulating test (DLST) for phenobarbital was positive. His symptoms, cardiomegaly, and cardiac function were improved by discontinuing phenobarbital followed by oral administration of prednisolone. We conclude that this eosinophilic myocarditis must have been induced by an allergic reaction to phenobarbital and that long-term eosinophilia contributed to the myocardial injury.