Hepatitis - Introduction

Chronic Hepatitis. The chronic forms of hepatitis persist for prolonged periods. Experts usually categorize chronic hepatitis by indications of severity as one of the following:

Chronic persistent hepatitis. Chronic persistent hepatitis is usually mild and nonprogressive or slowly progressive, causing limited damage to the liver.
Chronic active hepatitis. Chronic active hepatitis involves extensive liver damage and cell injury beyond the portal tract.

Click the icon to see an image of aggressive hepatitis.

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Viral Hepatitis

Most cases of hepatitis are caused by viruses that infect liver cells and begin replicating. They are defined by the letters A through G:

Hepatitis A, B, and C are the most common viral forms of hepatitis. Investigators are still looking for additional viruses that may be implicated in hepatitis unexplained by the current known viruses.
Other hepatitis viruses include hepatitis E and hepatitis G. Like hepatitis A, hepatitis E is caused by contact with contaminated food or water. It is not serious except in pregnant women, when it can be life threatening. Hepatitis G is always chronic with probably the same modes of transmission as hepatitis C, but to date it does not appear to have serious effects.

Scientists don?t know exactly how these viruses actually cause hepatitis (inflammation in the liver). As the virus reproduces in the liver, a number of proteins and enzymes, including many that attach to the surface of the viral protein, are also produced. Some of these may be directly responsible for liver damage. Researchers are investigating elevated levels of specific immune factors, including T-cell sub-types in the liver of hepatitis C and B patients. T-cells are important infection fighters in the immune system, which is some cases can release powerful inflammatory agents (e.g., tumor necrosis factor and interferon gamma) that can cause considerable damage leading to hepatitis B or C.

Autoimmune Chronic Hepatitis

Autoimmune chronic hepatitis accounts for about 20% of all chronic hepatitis cases. Like other autoimmune disorders, this condition develops because a genetically defective immune system attacks the body's own cells and organs (in this case the liver) after being triggered by an environmental agent, probably a virus. Suspects include the measles virus, a hepatitis virus, or the Epstein-Barr virus, which causes mononucleosis. It is also possible that a reaction to a drug or other toxin that affects the liver also triggers an autoimmune response in susceptible individuals. In about 30% of cases, autoimmune hepatitis is associated with other disorders that involve autoimmune attacks on other parts of the body.