Giant cell myocarditis is a disease of relatively young, predominantly healthy adults. The patients usually die of heart failure and ventricular arrhythmia unless a cardiac transplantation is performed. The term myocarditis refers to an autoimmune inflammatory response within the myocardium that is not secondary to ischemic events or cardiac rejection in the setting of transplantation. The incidence of giant cell myocarditis is low and it varies with the population which is being studied and the method of diagnosis which is used. In a Japanese autopsy registry, the incidence of giant cell myocarditis was 0.007%. There is no proven cure because of the unknown nature of the disorder.