HLA-DQA1*05 Associates with Extensive Ulcerative Colitis at Diagnosis: An Observational Study in Children.

The human leukocyte antigen (HLA) allele group HLA-DQA105 predisposes to ulcerative colitis (UC) and is associated with the development of antibodies against infliximab in patients with inflammatory bowel disease (IBD). Therefore, we hypothesized that the presence of HLA-DQA105 correlates with characteristics of pediatric IBD. Within a multi-center cohort in Poland, the phenotype at diagnosis and worst flare was established and HLA-DQA105 status was assessed enabling genotype-phenotype analyses. HLA-DQA105 was present in 221 (55.1%) out of 401 children with IBD (UC = 188, Crohn's disease = 213). In UC, the presence of HLA-DQA105 was moderately associated with a large extent of colonic inflammation at diagnosis (E4 55% more frequent in HLA-DQA105-positive patients, = 0.012). PUCAI at diagnosis ( = 0.078) and the time from UC diagnosis to the first administration of biologic treatment ( = 0.054) did not differ depending on HLA-DQA105 status. The number of days of hospitalization for exacerbation was analyzed in 98 patients for whom sufficient follow-up was available and did not differ depending on HLA-DQA105 carriership ( = 0.066). HLA-DQA1*05 carriers with CD were less likely to present with both stenosing and penetrating disease (B2B3, = 0.048) and to have active disease proximal to the ligament of Treitz (L4a) at the worst flare ( = 0.046). Future research focusing on explaining and preventing anti-TNF immunogenicity should take into account that ADA may develop not only as an isolated reaction to anti-TNF exposure but also as a consequence of intrinsic differences in the early course of UC.