Exploring the genetic role of the HLA-DPB1 locus in Chileans with intrahepatic cholestasis of pregnancy.

BACKGROUND/AIMS: Intrahepatic cholestasis of pregnancy is a rare disease of unknown etiology, with a strikingly higher prevalence in Chile than in most other countries. Although several studies suggest that a genetic predisposition is involved in the pathogenesis, no genetic disease-marker has so far been identified. Using a recently developed HLA-genotyping technique, we performed an association study with a highly polymorphic HLA class II gene in patients with recurrent intrahepatic cholestasis of pregnancy and normal control patients.

METHODS

Genomic DNA was extracted from 26 unrelated patients with recurrent ICP and 30 unrelated multiparous women without a personal or family history of this disease among a Chilean population. The polymorphic second exon of the HLA-DPB1 gene was amplified by the polymerase chain reaction and hybridized with 25 sequence-specific oligonucleotide probes to assign the HLA-DPB1 alleles on the basis of known sequence variations.

RESULTS

Out of more than 50 HLA-DPB1 alleles presently known, 13 were represented in the analyzed groups. Patients with ICP had a higher frequency of the allele DPB*0402 when compared to controls (69% vs 43%). This difference failed to reach statistical significance (x2 = 2.81, corrected p > 0.5). No significant differences were observed between the frequencies of other detected HLA-DPB1 alleles in the analyzed groups.

CONCLUSION

In this study, we observed a high frequency of the allele HLA-DPB1*0402 among Chilean patients with recurrent ICP, but no association of the disease with HLA-DPB1 alleles. Therefore, HLA-DPB1 alleles do not play a major role in determining susceptibility or resistance to intrahepatic cholestasis of pregnancy.