Eosinophilic myocarditis is a rare form of myocardial inflammation characterized by interstitial infiltration by eosinophils. Clinical presentation may vary from complete absence of symptoms to fulminant myocarditis with cardiogenic shock, to chronic heart failure due to progression to restrictive cardiomyopathy. The main causes of eosinophilic myocarditis are hypersensitivity reactions secondary to drug exposure, eosinophilic granulomatosis with polyangiitis, hypereosinophilic syndrome and infections. Antibiotics and agents acting on the central nervous system are the most frequently reported drugs capable of causing hypersensitivity myocarditis. Infections are usually due to intestinal parasites. Imaging techniques together with clinical and laboratory data help rising the suspicion of eosinophilic myocarditis. However, the definite diagnosis is made by endomyocardial biopsy. The evidence of eosinophilic infiltrate among myocytes allows to start an immunosuppressive treatment, usually based on corticosteroids, that are the cardinal therapy for eosinophilic myocarditis. Anticoagulation should be undertaken in case of endoventricular thrombosis, which frequently complicates eosinophilic myocarditis, mainly those cases associated with hypereosinophilic syndrome and eosinophilic granulomatosis with polyangiitis. In this focused review, we will try to provide answers to the most common questions on the causes, presentation, diagnosis, treatment, and outcomes of eosinophilic myocarditis.
