CBAS1 is a progressive liver disorder caused by a defect in the synthesis of bile acid. This defect results in intrahepatic cholestasis, jaundice, hepatomegaly, splenomegaly, cirrhosis, diarrhea, steatorrhea, malabsorption of lipids and lipid-soluble vitamins and a failure to thrive. The condition has a neonatal onset and often presents as neonatal cholestasis. However, in some cases it may only be identified later in life, when the disease has progressed further, often resulting in liver failure or death. The disorder is rare, with 1-9 affected individuals per one million live births.
Diagnosis is made based on liver function tests, laboratory analysis revealing increased serum bilirubin with decreased serum cholesterol and liver biopsy studies identifying giant cell hepatitis, nonspecific inflammation and fibrosis. The condition is treated with oral bile acid therapy.