Crigler–Najjar syndrome type I is a recessively inherited disorder characterized by severe unconjugated hyperbilirubinemia beginning at birth. The syndrome results from an absence of hepatic uridine diphosphoglucuronate (UDP) glucuronosyltransferase activity, which is essential for the conjugation and excretion of bilirubin. Because of the accumulation of unconjugated bilirubin in plasma, patients are at risk for kernicterus.¹ Although phototherapy successfully reduces serum bilirubin levels, patients are again at risk for kernicterus around the time of puberty, when phototherapy becomes less effective.² The necessary daily duration of phototherapy often approaches 14 to 16 hours. At present, liver transplantation is the only definitive treatment. . . .