Isolated unconjugated hyperbilirubinemia in adults: the Gilbert’s versus Criggler Najar Syndrome Type 2 conundrum.

Gilbert’s syndrome is a genetic disorder characterised by non-hemolytic unconjugated hyperbilirubinemia. It is caused by mutations in the UGT1A1 gene which codes for the enzyme uridine diphosphate glucoronosyl transferase-1, which conjugates bilirubin for excretion. Affected individuals are usually asymptomatic apart from a mild jaundice and investigations reveal a mild isolated indirect hyperbilirubinemia. This may be exacerbated in the face of environmental and physical stressors. It is very similar in presentation to Criggler-Najjar syndrome (CNS) type 2. There is a small risk of kernicterus in patients with CNS type 2 needing daily phenobarbitone therapy. This risk is miniscule in Gilbert’s syndrome. Genetic testing for polymorphisms of the UGT1A1 gene is the diagnostic clincher for Gilbert’s syndrome, but it can also be picked up by evaluating the response to phenobarbitone and fasting, particularly in resource poor settings. Due to limited availability, case reports documenting the genetic mutational analysis are sparse. We reported one such rare case with an unusually high indirect hyperbilirubinemia in Gilbert’s syndrome confirmed by both phenobarbitone response and genetic analysis.