Significance of troponin I level as a marker of disease activity in the management of acute necrotizing eosinophilic myocarditis with normal peripheral eosinophil count: a case report

BACKGROUND: Eosinophilic myocarditis is characterized by myocardial eosinophilic infiltration and is largely associated with hypereosinophilia. However, eosinophilic myocarditis with a normal peripheral eosinophilic count has been previously reported. Since the absence of eosinophilia poses a challenge for therapeutic management, we evaluated whether troponin I (TnI) levels can be used in the management of eosinophilic myocarditis where peripheral eosinophilia is absent. CASE SUMMARY: We report the case of a 77-year-old woman who developed cardiogenic shock due to acute necrotizing eosinophilic myocarditis, which required mechanical circulatory support. She did not have hypereosinophilia, but endomyocardial biopsy confirmed massive infiltration of eosinophils into the myocardium. We administered high-dose corticosteroids for 3 days and she dramatically improved. Along with this, the TnI level, which was elevated at the time of patient presentation, also decreased after steroid therapy. Troponin I level did not increase again without taking any oral prednisolone, and the follow-up biopsy after 6 months showed complete recovery of eosinophilic myocarditis. DISCUSSION: Troponin I-guided treatment is a useful tool in the management of eosinophilic myocarditis because it helps with therapeutic decisions, especially in the absence of eosinophilia.