OBJECTIVE: Crigler-Najjar Syndrome (CNS) is a rare genetic disorder due to a deficiency of the bilirubin-uridine diphosphate (UDT) glucuronosyltransferase enzyme activity resulting in pathological elevation of unconjugated bilirubin which can have devastating neurological sequelae. There are two type of CNS: CN type I and type II that may distinguish clinically. CN type I is characterized by complete or almost complete absence of UDT glucuronosyltransferase enzyme activity while CNS type II has reduced UDT glucuronosyltransferase enzyme activity. The incidence of CNS is 0.6 to 1 per million livebirth and to our limited knowledge this is the first case reported in Indonesia. 

CASE: A 12-year-old boy was admitted to our hospital due to depressed level of consciousness. He was found to be icteric and had history of recurrent seizures. Based on anamnesis this patient had persistent high-level bilirubin since 6-month-old. Total bilirubin level was 45.5 mg/dL and unconjugated bilirubin was 44.6 mg/dL. We performed emergency plasmapheresis due to crisis hyperbilirubinemia and reduced half of unconjugated bilirubinemia. His albumin and hemoglobin level were normal and from blood smear analysis revealed no hemolytic process. Those two conditions: severe unconjugated hyperbilirubinemia without hemolytic process suggest CNS. The patient was given phenobarbital but there is no significant response of therapy. We add phototherapy and bilirubin level can be decreased to 8-13 mg/dL. Definitive therapy, liver transplantation, is still being discussed to be performed in this patient. Gene analysis was performed in Centogene® showing homozygous variant of uncertain significance in the UGT1A1 gene (UGT1A1 variant c.1120G>A p.(gly374Ser). This type of missense mutation has never been reported before. 

CONCLUSION: Elevation of unconjugated bilirubin without hemolytic process should lead us to CNS. Phototherapy or phenobarbital may maintain safe level of unconjugated bilirubinemia in CNS. Plasmapheresis is useful in crisis hyperbilirubinemia