Virus-induced myocarditis in suspected sudden infant death syndrome. New knowledge from immunohistochemical und molecular pathological investigations

Virus-induced myocarditis is a common cardiac disease even in infants and children, but diagnosis can be difficult according to the Dallas criteria, which have been criticized as being too unreliable. The diagnosis has been substantially improved due to immunohistochemical techniques for characterization and quantification of myocardial inflammatory reactions as well as molecular pathological methods for viral genome detection. These new immunohistochemical and molecular pathological methods have confirmed the presence of viral infections and chronic myocarditis in a considerable number of cases of suspected sudden infant death syndrome. The published studies report on postmortem samples from SIDS victims and controls which were prospectively investigated. Pediatric cases of unnatural death served as controls. Myocardial samples were studied for enteroviruses, adenoviruses, parvovirus B19, Epstein-Barr viruses and cytomegalovirus applying the polymerase chain reaction. Immunohistochemical investigations were performed for LCA(+) leucocytes, CD45R0(+) T-lymphocytes and CD68(+) macrophages as well as for the early necrosis marker C5b-9((m)) complement complex and the enteroviral capsid protein VP1. In addition, the expression of the inflammatory MHC class II molecules and the endothelial expression of E-selectin were detected. All the viruses tested were found in the myocardium in cases of suspected SIDS. Control group samples were completely virus negative. Compared to the controls, immunohistochemical investigations partially revealed an increase in the number of CD45R0(+) T-lymphocytes in myocardial samples in SIDS. Furthermore, cases with elevated numbers of LCA(+) leucocytes and CD68(+) macrophages, microfocal C5b-9((m))(+) necrosis and enteroviral VP1 capsid protein within the myocardium were detected. The results demonstrate a clearly higher prevalence of viral myocardial infections in cases of suspected SIDS. Preliminary criteria for cellular immunohistochemical diagnosis of viral myocardial affections derived from these findings are suggested.