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

: 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 DPB1*0402 when compared to controls (69% vs 43%). This difference failed to reach statistical significance (χ2=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.