IgG anti-cardiomyocyte antibodies in giant cell myocarditis.

Giant cell myocarditis, a rare, fatal, and poorly understood cause of myocarditis, requires pathological examination for diagnosis. It is considered to be an autoimmune disease and is frequently associated with other conditions, in particular thymoma and myasthenia gravis. The typical patient with giant cell myocarditis is young and has severe, progressive congestive cardiac failure that is unresponsive to standard medical therapy and ultimately requires cardiac transplantation. Hence giant cell myocarditis is the most dangerous form of myocarditis. Here we report an unusual presentation of giant cell myocarditis, which mimicked acute myocardial infarction in an elderly woman with myasthenia gravis and a previous diagnosis of thymoma. This patient had evidence of anti-myocyte antibodies, consistent with an autoimmune mechanism.