A causal relationship between UDP-glucuronosyltransferase 1A1 promoter polymorphism and idiopathic hyperbilirubinemia in Turkish newborns.

The etiology of pathological jaundice can not be identified in almost half of the cases. The effect of promoter polymorphism in the UDP-glucuronosyltransferase 1A1 (UGT1A1) gene was investigated in healthy breast-fed Turkish neonates with unexplained and direct Coombs'-negative ABO incompatible hyperbilirubinemia. Newborns whose peak serum bilirubin levels were > or = 17 mg/dl and < or = 12.9 mg/dl within the first week of life formed the idiopathic hyperbilirubinemia (n: 50) and control (n: 54) groups, respectively. Thymine-adenine (TA) repeats in the promoter region of the UGT1A1 gene were investigated by polymerase chain reaction (PCR)-based non-radioactive DNA sequencing. In the idiopathic hyperbilirubinemia group, higher peak bilirubin levels, higher heterozygous and variant homozygous genotypes, higher TA7 allele frequencies, and shorter peak time were observed (p < 0.001, p < 0.001, p < 0.001, p < 0.05, respectively). In conclusion, healthy breast-fed Turkish neonates who carry heterozygous and variant homozygous genotypes in the UGT1A1 gene are at high risk of developing significant hyperbilirubinemia without additional icterogenic factors.