Autoimmune hepatitis is a condition in which a person's own immune system attacks the liver, causing swelling and liver cell death. The swelling continues and gets worse over time. If not treated, this can lead to permanent cirrhosis (a disease of the liver caused by liver cells that do not work properly), and eventually liver failure.

Autoimmune hepatitis is classified as either type I or II.

Type I is the most common form in North America. It occurs at any age and is more common in females.

Type II is less common overall, but more common in children. It often affects girls ages 2 to 14.