Usefulness of eosinophilic cationic protein as a marker of eosinophilic myocarditis in a child

Eosinophilic myocarditis is characterized by an acute inflammatory infiltration of eosinophils in the myocardium. Diagnosis is confirmed by a heart muscle biopsy. Immunopathological studies suggest that several toxic proteins, such as eosinophilic cationic protein (ECP) derived from the degranulation of eosinophils, may play an important role in the patho- genesis of this cardiac disorder. Serum levels of ECP, which are related to the inflammatory activity of the disease are used to monitor and determine the effects of treatment in adult patients. Herein, we present the case of a 12-year-old, previously healthy, junior high school girl with eosinophilic myocarditis. The diagnosis was confirmed by a myocardial biopsy and the patient was treated successfully with prednisolone. On admission, her peripheral blood eosinophil count (3342 /μL) and serum ECP level (124 μg/L) were extremely high, but both decreased significantly during corticosteroid therapy. In the present case, corticosteroid treatment was successful and early diagnosis by endomyocardial biopsy is recommended. Furthermore, serum ECP is useful to monitor the efficacy of treatment in pediatric patients.