Clinical aspects of non-A, non-B hepatitis infection.

Although non-A, non-B hepatitis is usually a mild subclinical illness, 40% of cases of fulminant viral hepatitis are attributed to infection by this agent. The administration of coagulation factor IX concentrates before liver biopsy in 17 patients with chronic liver disease was followed by the development of hepatitis in four, which proved fatal in three cases. The diagnosis was confirmed by transmission in chimpanzees, and further studies demonstrated the existence of two types of non-A, non-B hepatitis with different incubation periods and specific ultrastructural changes in the hepatocytes. The progression of 40% of cases of acute viral hepatitis to chronic liver disease and the development of chronic liver disease in renal and hepatic transplant recipients is very disturbing. It is likely that this type of hepatitis is an aetiological factor in some cases of hepatitis B surface antigen-negative chronic active hepatitis.