A mild increase of serum bilirubin levels is also observed in the Gilbert syndrome, a benign condition caused by a TA-insertion in the TATA box of UGT1A1 promoter [A (TA)7TAA] (termed UGT1A1*28; instead of the normal TA6), leading to 50%–70% reduction in UGT1A1 gene expression (Strassburg, 2010). The gene discussed is UGT1A1; the disease is Gilbert syndrome.