Extrahepatic manifestations of hepatitis C infection.

Hepatitis C virus (HCV) affects 1.8% of the American population, and approximately 38% of patients with HCV will manifest symptoms of at least 1 extrahepatic manifestation during the illness. Renal disease, neuropathy, lymphoma, and Sjögren syndrome with or without mixed cryoglobulinemia are all strongly associated with HCV infection. Porphyria cutanea tarda and diabetes have also been linked to HCV. Most extrahepatic manifestations of chronic HCV infection are immunological, and the chronic infection seems to be necessary for their development. The molecular study of the unique way in which the HCV virus interacts with the human immune system is beginning to provide plausible explanations of the pathogenic role of HCV in some of these syndromes, but many pathogenetic links remain completely obscure.