Crigler–Najjar syndrome is an autosomal recessive disorder marked with unconjugated hyperbilirubinemia, potentially leading to brain damage (Kernicterus). The incidence of this disease is estimated to be 0.6–1 per million live births, making it an extremely rare disorder. Crigler and Najjar were the first to describe this disease in a consanguineous American family in 1952. Crigler–Najjar syndrome causes severe jaundice in the first few days of life. Neonates with Crigler Najjar type I, the severe form of disease, may develop Kernicterus within weeks if left untreated. Crigler Najjar type II is less severe and responds dramatically to treatment with phenobarbital.