Viral myocarditis.

Evidence suggests that in susceptible individuals lymphocytic myocarditis is a virus-induced autoimmune disease which may progress to dilated cardiomyopathy. Its biopsy pathology, the application of the 'Dallas' criteria for diagnosis and the role of immunohistochemistry are discussed. The potential role for in situ hybridization in the detection of viral genomes is referred to. Pathogenesis may be related to persistence of viral RNA in tissues and may involve both cellular and humoral immune mechanisms. The effect may manifest itself at cellular level with myocytolysis or at sub-cellular level with interference in energy production, giving rise to considerable functional deficit with few morphological changes.