The role of Coxsackie B viruses in the pathogenesis of myocarditis, dilated cardiomyopathy and inflammatory muscle disease.

Coxsackie B viruses are members of the family Picornaviridae which have been associated by retrospective serology with a range of muscle diseases, particularly myocarditis, dilated cardiomyopathy and epidemic pleurodynia (epidemic myalgia or Bornholm disease). It has been proposed that virus-induced myocarditis disposes to the development of idiopathic dilated cardiomyopathy. However, despite many attempts, isolation of infectious virus or immunofluorescent detection of virus-specific antigens in the affected tissue is rare, although virus may be found in faeces early in infection. This discrepancy awaited the development of nucleic acid probes to resolve the problem of whether virus was present consistently in myocardium or other muscle tissues. We report here the synthesis of Coxsackie B virus-specific complementary DNA (cDNA) probes and their use in molecular hybridizations to quantitative slot-blots of RNA prepared from either endomyocardial or skeletal muscle biopsy specimens. Of 50 patients with histologically proven myocarditis or dilated cardiomyopathy, 28 (56%) had an endomyocardial biopsy specimen positive for the presence of Coxsackie B virus-specific RNA. Twenty-two patients with other cardiac diseases of known aetiology, unrelated to virus infection, were all negative. Multiple biopsies were obtained from 20 patients with myocarditis or dilated cardiomyopathy and 15 of these (75%) had at least one biopsy specimen positive, indicating the focal nature of the disease. In analogous investigations, Coxsackie B virus-specific RNA was detected in four out of seven single skeletal muscle biopsy specimens from patients suffering from juvenile dermatomyositis, and one out of two patients with adult polymyositis. Ten muscle controls, either normal or Duchenne muscular dystrophy, were negative for virus RNA.