Giant cell myocarditis of the left atrium.

Here we describe an unusual case of giant cell myocarditis (GCM) found in the left atrial appendage. Giant cell myocarditis is a rare entity in itself, while isolated left atrial GCM has only been reported on a few occasions. We describe a patient who underwent mitral valve replacement for rheumatic mitral stenosis and excision of a grossly abnormal, thickened, and enlarged left atrial appendage. Histological examination confirmed the presence of GCM.