A rare disorder in which there are defects in the small tubes that carry bile (fluid that helps digest fat) out of the liver. These small tubes may be narrow or have an abnormal shape, or there may be fewer of them than normal. This can cause bile to build up in the liver, which may lead to cirrhosis (scarring of the liver) and liver damage. Alagille syndrome can also affect other parts of the body, including the heart, kidneys, blood vessels, eyes, face, and spine. It usually occurs in infants and children and may be inherited.