“Occult” HCV infection has been defined as detection of HCV RNA in liver tissue alone or in liver tissue as well as in peripheral blood mononuclear cells (PBMCs) despite constantly undetectable levels of HCV RNA in serum. 15 Two forms have been distinguished:(1) detection of HCV RNA in liver tissue of patients with liver disease of unknown origin (anti-HCV negative, serum HCV RNA negative) and (2) detection of HCV RNA in liver tissue in patients with spontaneous or treatment-induced HCV RNA clearance from serum (anti-HCV positive, serum HCV RNA negative). 8, 10