A case of biopsy-proven eosinophilic myocarditis related to tetanus toxoid immunization.

Vaccine-associated myocarditis is an extremely rare, yet potentially lethal disease, which requires early diagnosis and prompt treatment. However, its pathogenesis remains elusive. We report the first case of biopsy-proven eosinophilic myocarditis related to tetanus toxoid immunization, with unique histopathologic findings, characterized by perivascular eosinophilic infiltrates with myocyte necrosis and abundant interstitial lymphocytic infiltrates with myocyte necrosis, separately. A systemic high-dose corticosteroid treatment had a dramatic beneficial effect on hemodynamic instability and resulted in complete recovery. This case highlights the value of endomyocardial biopsy in establishing a definite diagnosis and understanding the pathogenesis of vaccine-associated myocarditis.