The pathogenesis of dilated cardiomyopathy (DCM) is still unknown; however, some factors that seem to play an important role in the development of the disease have recently been identified: they are enteroviral infections, immune mechanisms and genetic factors. Enteroviral infection (particularly due to Coxsackie virus B) has long been suspected to be the cause of myocarditis and subsequent DCM. However, only recent techniques of genetic engineering have been able to demonstrate the presence of enteroviral RNA in endomyocardial biopsy of patients with DCM. The role of the viral particles contained in the myocardium is still undetermined. Changes in the immune system concerning cell-mediated and humoral immunity have been recently detected. It has been suggested that an autoimmune process could be the actual cause of DCM in some patients, rather than the consequence. The immune system is strictly related to the major histocompatibility complex. As in some autoimmune diseases, a relationship between DCM and HLA class II phenotype has been found: particularly the DR4 antigen seems to be associated with a high risk of disease. Besides immunogenetic factors, other genetic factors seem to play a role in the pathogenesis of DCM. In 6-8\% of cases a familial history of cardiomyopathy has been observed. In clinical studies on familial DCM different phenotypes have been shown, suggesting that different genetic mechanisms are involved in the pathogenesis of the disease. At least two main mechanisms can be hypothesized: the transmission of "predisposing" factors or a defect in proteins essential for the cardiac muscle cell function. Viral agents, autoimmune reactions, immunogenetic and genetic factors seem to cause myocardial damage individually or with complex interactions: the research should be devoted to these topics in the future.
