Introduction In approximately half of the cases there are no identified risk factors associated with pathological neonatal hyperbilirubinaemia. We studied whether unexplained newborn hyperbilirubinaemia is associated with genetic factors and aimed to determine the prevalence of UGT1A1, G6PDH gene polymorphisms and OATP-2 gene mutation.

Materials and Methods Newborns whose serum bilirubin levels were ⩾256 mmol (15 mg/dl) were enrolled. Sixty-five newborns, 37 neonates and 53 healthy neonates were included in the jaundice with unknown aetiologies group, with known aetiologies group and control group, respectively. Genomic DNA was isolated from blood samples with the use of a DNA isolation kit (Maxim Biotech Inc, San Fransisco, California, USA). PCR restriction fragment length polymorphism was applied to detect the polymorphisms in the genes for UGT1A1, G6PDH and OATP 2. The obtained DNA sequences were investigated manually in Vector NTI Suite (İnvitrogen, USA) and confirmed at the web server of NCBI (National Center for Biotechnology Information) from www.ncbi.nih.gov.

Results and Conclusion UGT1A1 gene polymorphism with a G→A mutation in heterozygous form at nucleotide 211 was detected in 4.6% of the hyperbilirubinaemic group with unknown aetiologies, 2.7% of the hyperbilirubinaemic group with known aetiologies and 5.6% of the control group (p>0.05). 1376 G→T and 563 C→T mutations in the gene of G6PDH did not exist in any of the 155 neonates enrolled in the study. Male gender (odds ratio (OR) 3.08), variations at the nucleotide 388/411–411 (OR 3.6) and 388–411 (OR 2.4) of OATP2 gene were found to be risk factors for the jaundice group with unknown aetiologies.