Etiopathogenetic role of hepatitis C virus in mixed cryoglobulinemia, chronic liver diseases and lymphomas.

Hepatitis C virus (HCV) infection has been found in the majority of patients with mixed cryoglobulinemia (MC) in studies conducted in different countries. In our series of 110 MC patients the frequency of HCV markers was significantly high (91%) compared with other rheumatic diseases (6.4%) and with healthy Italian controls (1.2%). Moreover, HCV RNA was detected in 81% of the peripheral lymphocytes from MC patients. Comparable percentages of HCV infection were detectable in other disorders, i.e. porphyria cutanea tarda (77%) and autoimmune hepatitis type 1 (77%). The HCV infection of peripheral lymphocytes suggests that this virus could be the triggering factor for the lymphoproliferation underlying MC. In a number of patients with MC the evolution from a benign lymphoproliferation to frank B-cell lymphoma was observed. In these subjects HCV RNA in the sera and in fresh and cultured peripheral lymphocytes was constantly detected. The same phenomenon has been observed in patients with long-lasting type C chronic hepatitis. Interestingly, HCV infection has also been recorded in 32% of idiopathic B-cell non-Hodgkin's lymphomas. Taken together, the above findings suggest that HCV can cause benign B-cell proliferation with the consequent production of various autoantibodies, including rheumatoid factor and mixed cryoglobulins. These serological abnormalities characterise different clinical disorders, including the appearance of lymphoma in a not negligible number of individuals.