Prolonged unconjugated hyperbilirubinaemia associated with the haem oxygenase-1 gene promoter polymorphism

To elucidate the genetic factors causing hyperbilirubinaemia in prolonged jaundice of the newborns, we investigated whether the HO-1 gene promoter polymorphism is a cause in unexplained pathological or prolonged jaundice.

Three groups were defined: healthy newborns with no clinical jaundice, newborns hospitalized for jaundice without any identifiable pathological cause and newborns with prolonged jaundice associated with breast milk. Genomic DNA was extracted from the white blood cells and the promoter region of the HO-1 gene was amplified using PCR and their allelic repeats were determined.

We did not detect any significant difference in the allele frequencies between the healthy newborns and the newborns whose serum total bilirubin levels were >12.9 mg/dL. However, the patients with short (<24 GT) dinucleotide repeat in the HO-1 gene promoter on either allele had significantly higher prolonged unconjugated hyperbilirubinaemia than the healthy newborns. There was no significant difference between the groups 2 and 3.

The results indicate that polymorphism of HO-1 gene promoter region can be an underlying cause of the prolonged unconjugated hyperbilirubinaemia associated with breast milk. In this patient population, short repeat alleles of the HO-1 gene promoter polymorphism were associated with prolonged jaundice.