Inborn errors of bile acid metabolism have been established as a well recognized cause of neonatal cholestasis and fat-soluble vitamin malabsorption. Although there is extensive experience with metabolic defects in the biosynthetic pathway, few patients have identified with defects in conjugation with taurine or glycine that allows bile acids to become effective detergents. This protocol is designed to study the effect of defects of conjugation of bile acids on growth and fat-soluble vitamin malabsorption. Study subjects will have liver function studies performed, serum and urinary bile acid measurements, vitamin levels, growth measurements, bile acid pool size measurements made by stable isotope dilution mass-spectrometry, and measurements of absorption of two fat-soluble vitamins, tocopherol and vitamin D. Subjects will be treated orally with conjugates of cholic acid with follow-up laboratories performed as an outpatient and then subjects will have all of the initial studies repeated during an inpatient stay 3-12 months after starting treatment. Subjects with previous liver biopsies indicating the presence of significant liver disease will have a repeat liver biopsy after 3-12 months treatment to assess the histologic response to treatment.
