Allele and haplotype frequencies for HLA class II (DQA1 and DQB1) loci in patients with celiac disease from Spain.

Celiac disease (CD) is a complex and multifactorial disease, defined as a malabsorptive disorder of the small intestine resulting from ingestion of gluten. Genetic susceptibility to CD has been associated with human leukocyte antigen (HLA)-DQ2 heterodimer, encoded by the DQA1*0501 and DQB1*02 genes. However, HLA risk factors do not explain the whole genetic predisposition: not all DQ2-encoding haplotypes confer equal susceptibility to CD. The aim of the present work was to confirm the aforementioned findings in a southern European population. With this purpose, 136 unrelated children diagnosed with CD were typed at the DNA level for HLA-DQA1 and -DQB1 loci. Patients are currently attended at the Donostia Hospital (province of Guipúzcoa, Spain). HLA class II typing was performed by polymerase chain reaction-sequence specific primer procedures. Conspicuous frequencies of the alleles associated with susceptibility to CD were observed (DQA1*0501: 0.592, DQB1*0201: 0.471). Accordingly, the haplotypes DQA1*0501-DQB1*0201 and DQA1*0201-DQB1*0202 revealed a strong linkage disequilibrium (18.84% and 18.75%, respectively) when compared with the Spanish general population. Of the total sample, 93.4% (127 individuals) were carriers of DQ2 heterodimer, either in homozygosis or in heterozygosis. This percentage coincides with figures reported in previous studies, implying the effect of other genes in the development of CD.