Crigler-Najjar syndromes (CN) are inborn disorders of the liver metabolism of bilirubin characterized by non-hemolytic unconjugated hyperbilirubinemia. CN are classified into two types based on the bilirubin levels, the presence of kernicterus and the reduction of the bilirubin levels upon administration of Phenobarbital or other enzyme-inducing agents.
Mutations in the UGT1A1 gene [OMIM #191740] have been identified in patients with CN. The UGT1A1 gene maps to 2q37.1. It has 4 coding exons, and to date missense, nonsense, frameshift and splice site mutations, and small insertions and deletions have been described.
Deletions and/or duplications involving UGT1A1 as causative of Crigler-Najjar syndrome have been reported.