Hepatitis is an inflammation of the liver characterized by diffuse or patchy necrosis.
Common causes of hepatitis include
At least 5 specific viruses appear to be responsible for hepatitis (see table Characteristics of Hepatitis Viruses). Other unidentified viruses probably also cause acute viral hepatitis.
Less common causes of hepatitis include autoimmune disorders, genetic liver disorders, and other viral infections (eg, infectious mononucleosis, yellow fever, cytomegalovirus infection) and leptospirosis.
Parasitic infections (eg, schistosomiasis, malaria, amebiasis), pyogenic infections, and abscesses that affect the liver are not considered hepatitis. Liver involvement with tuberculosis (TB) and other granulomatous infiltrations is sometimes called granulomatous hepatitis, but the clinical, biochemical, and histologic features differ from those of the diffuse liver involvement in hepatitis caused by hepatitis viruses, alcohol, and drugs.
Various systemic infections and other illnesses may produce small focal areas of hepatic inflammation or necrosis. This nonspecific reactive hepatitis can cause minor liver function abnormalities but is usually asymptomatic.
Some types of infectious and noninfectious liver inflammation are summarized in table Selected Infections With Liver Involvement.