Severe mitral valve dysfunction due to unsuspected granulomatous myocarditis: successful cardiac transplantation following attempted mitral valve repair.

Granulomatous involvement of the myocardium is a rapidly fatal disease of uncertain aetiology rarely diagnosed premorbidly. We report a patient who presented with mitral valve incompetence and congestive cardiac failure who underwent a successful mitral valve repair but could not be weaned from cardiopulmonary bypass. Urgent heart transplantation was successfully performed and histological studies of the explanted heart revealed granulomatous myocarditis involving the mitral subvalvular apparatus. Endomyocardial biopsy may be necessary in young patients presenting with mitral valve disease of unknown aetiology.