Review article: non-alcoholic fatty liver disease and hepatitis C--risk factors and clinical implications.

Hepatitis C and non-alcoholic fatty liver disease (NAFLD) are the two most common liver diseases in the Western hemisphere. It is therefore natural that these conditions often co-exist in the same individual. Hepatitis C, especially genotype 3, is often associated with hepatic steatosis. In subjects with genotype 3 infection, a sustained virologic response to treatment is associated with improvement in hepatic steatosis. The diagnosis of NAFLD in a subject with hepatitis C infection is based on the presence of hepatic steatosis. Most investigators require the presence of at least grade II steatosis to warrant a diagnosis of concomitant NAFLD because the significance of minimal steatosis is uncertain. The presence of steatohepatitis is surmised by the additional presence of Mallory bodies, cytologic ballooning and pericellular fibrosis. It is of paramount importance to exclude alcohol as a cause of these histologic findings in this population before a diagnosis of NAFLD is made. The presence of NAFLD in subjects with hepatitis C genotype 1 infection is most strongly associated with the presence of the metabolic syndrome and insulin resistance. The degree of hepatic steatosis correlates with the degree of hepatic fibrosis and the presence of concomitant steatosis is associated with more advanced fibrosis. The presence of cytologic ballooning confers an additional risk for increased fibrosis. Insulin resistance and hyperinsulinemia have been associated with increased collagen production by hepatic stellate cells. Subjects with hepatitis C and NAFLD are more likely to be virologic nonresponders following anti-HCV therapy. The value of treating insulin resistance and NAFLD prior to antiviral therapy remains to be experimentally verified.