This is a relatively uncommon disorder that is due to a partial deficiency of UDP-GT activity. This results in a lifelong persistent unconjugated hyperbilirubinemia. Plasma levels of unconjugated bilirubin range from 6 to 25 mg/dl. The only abnormal clinical presentation is jaundice, which will usually present itself within the first year of life. Kernicterus is infrequent, and thus, patients will develop normally without neurological impairment. As in Cigler-Najer type I, the problem is not excessive bilirubin production, but hepatic bilirubin clearance. In contrast to Crigler-Najer type I, type II will respond to phenobarbital administration within approximately 2 to 3 weeks. Phenobarbitol (30-60 mg PO TID) enhances bilirubin clearance in type II disease.