HLA-DQ2-negative celiac disease in Finland and Spain

Genetic susceptibility to celiac disease (CD) is strongly associated with DQA1*0501 and DQB1*02 (= DQ2). To study whether CD patients without DQ2 share other MHC class II or TNF alleles, we screened DQ2-negative patients in Finland and Spain. Twelve of 84 (14%) Finnish patients and 13 of 189 (6%) Spanish patients were negative for DQ2. We observed that all but two of altogether 25 DQ2-negative patients had the DR4 DQ8 haplotype, or either DQA1*0501 or DQB1*02 alone. Also, all but three were positive for DRB4*01. The only patients without any of these alleles were both positive for DR 13. There was a clear difference between Finland and Spain: Ten (83%) of the 12 Finnish DQ2-negative patients but only five (38%) of the 13 Spanish patients had DRB1*03, DQA1*03, DQB1*0302 (= DQ8) alleles. Of the Spanish patients, eight (62%) had DQB1*02 without DQA1*0501 and three (23%) had DQA1*0501 without DQB1*02. None of the TNF, TAP, or DPB1 alleles was found to be significantly associated with CD. Our results indicate that in addition to the DQ2 heterodimer, the other major risk alleles for CD are DR4 DQ8, and either DQA1*0501 or DQB1*02 alone. Patients without these alleles appear to be very rare, only two (0.7%) were identified in altogether 253 patients tested.