Alagille syndrome (AGS) is a complex multisystem disorder involving primarily the liver, heart, eyes, face, and skeleton. The major signs of AGS are cholestasis, heart defects, eye defects; typical facial features; and "butterfly" vertebrae. These features are highly variable, even within families. JAG1 is the only gene known to be associated with Alagille syndrome. It is inherited in an autosomal dominant manner with about 30-50% of individuals inheriting the disease and about 50-70% have a de novo mutation.