Mild unconjugated hyperbilirubinemia, known as “Gilbert’s syndrome”, has a prevalence of 5–10% in Caucasians and is associated with a polymorphism of the 5′ end of the UGT1A1 gene promoter, a homozygous insertion of thymine–adenine (TA) pairs (genotype UGT1A1*28/*28) [18]. Here, UGT1A1 is linked to Gilbert syndrome.