Autoimmune hepatitis

Autoimmune hepatitis is a liver disease. "Hepatitis" means inflammation of the liver, and in this case that inflammation is chronic, meaning it lasts, and progressive, meaning it keeps getting worse. No one knows yet what causes it, and it shows up more often in women than in men.

Here is how it's currently thought to happen. Your immune system, the body's defense force, normally recognizes your own cells and leaves them alone. That's called immune tolerance. Picture the security guards in an apartment building who carry a list of everyone who lives there and don't bother anyone on it. In a person with a certain genetic tendency, that tolerance breaks down, as if the guards lost the list, and something in the environment, like an infection, a medication, or a toxin, sets things off. From then on, T cells, a type of white blood cell, drive ongoing inflammation aimed at the person's own liver.

That inflammation settles mostly in the portal tracts, small areas of the liver where blood vessels and bile ducts run through. From there it destroys hepatocytes, the cells that make up the liver, right along the edge where those areas meet the rest of the organ. That damage along the edge is called interface hepatitis. Over time it can get worse: fibrosis, which is scar tissue, forms in bands that link one area to another (bridging fibrosis); regenerating nodules, small clumps of new cells, take shape; and in the end it can reach cirrhosis, the most advanced stage of that scarring.