UGT1A1 and Hyperbilirubinemia: Serum TB is highly variant across GS patients and fluctuates within individuals across different time periods.[42] Although UGT1A1 polymorphism is associated with the pathogenesis of GS, UGT1A1 genotype does not fully explain the variability among patients nor the variability over time within patients.[1] Here, we observed only a weak positive correlation between UGT1A1 mutation load and bilirubin level (γ = 0.281), which suggests that there are other factors that contribute to GS unconjugated hyperbilirubinemia.