A case of eosinophilic myocarditis

A 83-year-old female presented with shortness of breath and was found to be in acute decompensated heart failure with a reduced ejection fraction. Bloodwork revealed significant eosinophilia and endomyocardial biopsy confirmed eosinophilic myocarditis. One month prior, she had been hospitalized for a new diagnosis of heart failure while on vacation in Colorado. During that hospitalization, work-up included a heart catheterization showing non-obstructive coronary disease leading to a new diagnosis of non-ischemic cardiomyopathy. Bloodwork at that time showed a normal eosinophil count. She had been given prednisone for a suspected asthma exacerbation a few days prior to presentation likely normalizing the eosinophil count. We report a case of eosinophilic myocarditis and the difficult diagnostic dilemma it presents due to low incidence, broad clinical symptoms, and past medical history that can confound the diagnosis. A thorough work-up was completed, and in this patient’s case, the etiology was likely drug-induced from the home medication hydrochlorothiazide.