[Extrahepatic manifestations of HCV infection].
It is well known that hepatitis C virus (HCV) can replicate outside the liver, particularly in the blood mononuclear cells. This fact may account for the systemic involvement, primarily due to immune-mediated mechanisms, which is commonly observed in patients affected with chronic hepatitis C. In this review the main extra-hepatic manifestations of the HCV infection are described and classified, according to the clinical involvement, namely dermatological, haematological, rheumatological, endocrinological, ophthalmological ad respiratory syndromes. In particular, the well-established causative role of HCV in determining certain clinical disorders, i.e., mixed cryoglobulinaemia and porphyria cutanea tarda, where the anti-HCV seroprevalence is higher than 70%, is emphasized. Moreover, some problems relevant to the diagnosis of the HCV infection in a proportion of autoimmune diseases (for example, primary Sjogren's syndrome), are discussed. Indeed, in these clinical disorders, hypergammaglobulinaemia, which represents an interfering factor with the results obtained by the screening anti-HCV tests, is a typical serologic feature.