Immunoglobulin G4-Related Myocarditis with Eosinophilic Infiltration: A Case Report.

Immunoglobulin G4 (IgG4)-related disease (IgG4-RD) is a fibroinflammatory disorder that can involve any organ system; however, myocarditis is extremely rare. A 52-year-old male with dyspnea and chest discomfort underwent cardiac MRI that revealed edema and nodular, patchy, mesocardial and subendoardial delayed enhancement of left ventricle, suggesting myocarditis. Laboratory findings revealed elevated serum IgG4 and eosinophilia. Cardiac biopsy confirmed eosinophilic myocarditis with IgG4-positive cells. Here, we present an unusual case of IgG4-RD manifesting as eosinophilic myocarditis.