Background: Crigler-Najjar syndrome (CNs) presents as unconjugated hyperbilirubinemia, as a result of UGT1A1 deficiency, and can be categorized in a severe (type I) and mild (type II) phenotype. CNs type II patients usually benefit from phenobarbital treatment that induces residual UGT1A1 activity.
Case Presentation: Here we present a CNs type II patient that is not responsive to phenobarbital treatment, which can be explained by two heterozygous mutations in the UGT1A1 gene.