[A patient of polymyositis with severe myocardial damage and conduction block]

A patient with polymyositis manifesting severe myocardial damage and conduction block is described. A 57-year-old man presented dysarthria, dysphagia, proximal-dominant muscle weakness and wasting of the extremities. Muscle biopsy revealed degeneration and regeneration of muscle fibers and infiltration of mononuclear cells. After admission, muscle weakness rapidly progressed and mechanical ventilation was needed for respiratory failure. Simultaneously, cardiac symptom developed and resulted in bradycardia and trifascicular conduction block, which required a pacemaker. Echocardiogram revealed diffuse hypokinesia, ventricular enlargement and thickened wall. Marked elevations of serum CK-MB, cardiac myosin light chain I and cardiac troponin T were observed. High dose administration of methylprednisolone resulted in improvement of muscular and cardiac symptoms, and prevented complete heart block. Immediate and high dose of steroid therapy was considered to be effective for severe myocarditis in polymyositis.