ACUTE HEPATITIS

Acute hepatitis may be caused by a large number of different viruses, the most important of which are the hepatitis B virus (HBV), the hepatitis A virus (HAV) and the non-A, non-B (NANB) group. Clinical and morphological features of all three types of infection are similar. Hepatitis is the predominant manifestation of yellow fever, and is a common feature of cytomegalovirus infection and infectious mononucleosis, caused by the Epstein-Barr virus. Less commonly, the liver may be involved in disseminated herpes simplex infection and in varicella (chickenpox). Nonviral forms of acute hepatitis include Q fever, bacterial hepatitis, leptospirosis and Reye's syndrome.

Pathologically, viral hepatitis is characterized by spotty necrosis scattered throughout the liver lobule with varying degrees of degeneration of liver cells, including necrosis, infiltration of the liver by mononuclear cells and variable degrees of cholestasis . In HBV infections, `ground-glass' hepatocytes and specific staining of HBV surface antigen may be demonstrated and . Hepatic cell necrosis is usually focal and limited in extent, but occasionally, especially in HBV infection, massive hepatic necrosis (acute yellow atrophy) occurs with loss of nearly all liver cells and complete collapse of the hepatic architecture and . As discussed below, some types of viral hepatitis may persist and produce chronic lesions in the liver, including postnecrotic cirrhosis.