Significant association of HLA-A26 with uveitis and gastrointestinal involvement in patients with Behçet's disease in a multicentre study

Objectives Specific human leukocyte antigen (HLA) haplotypes are associated with Behcet's disease. Because the effects of HLA-A26 and its combination with HLA-B51 on organ involvement in Behcet's disease have not been well demonstrated, we aimed to examine them.Methods This multicentre, cross-sectional, observational study enrolled patients with Behcet's disease who visited Kyoto University Hospital between 2018 and 2021 or Kurashiki Central Hospital between 2006 and 2016 (n = 200). Disease severity was evaluated using the Krause score.Results Uveitis and gastrointestinal involvement were observed in 95/196 and 57/167 patients, respectively. The HLA alleles identified were HLA-B51 (n = 52/106), HLA-A26 (n = 25/88), and HLA-B51 and HLA-A26 (n = 6/88). In patients harbouring HLA-B51, the presence of HLA-A26 was associated with higher frequencies of uveitis (P = .03) and coexistence of uveitis and gastrointestinal involvement (P = .002) and higher Krause scores (P = .02). Furthermore, the presence of HLA-A26 was associated with a higher frequency of uveitis in patients with gastrointestinal involvement (P = .001) and gastrointestinal involvement in patients with uveitis (P = .001).Conclusions Since specific HLA haplotypes and their combinations are associated with organ involvement, both HLA-A and HLA-B haplotypes should be confirmed when screening for affected organs.