Immunoglobulin G4-related disease of the heart causing aortic regurgitation and heart block.

Immunoglobulin (Ig) G4-related disease is a novel disease entity characterized by diffuse lymphoplasmacytic infiltrates and the presence of abundant IgG4-positive plasma cells in extensive fibrosis, frequently associated with tumorous swelling lesion and elevated serum IgG4 concentrations. Immunoglobulin G4-related disease has been described in almost every organ system but rarely affects the heart. We describe a rare case of IgG4-related disease of the heart causing aortic regurgitation and heart block in a 59-year-old woman. The excised lesion revealed a high ratio of IgG4-positive to IgG-positive plasma cells, providing a definite diagnosis of IgG4-related disease. The aortic valve was replaced using Manouguian technique, resulting in a favorable outcome.