The MYO9B gene is a strong risk factor for developing refractory celiac disease.

Background & Aims: Celiac disease (CD) is associated with HLA-DQ2and HLA-DQ8 and has been linked to genetic variants in the MYO9B gene on chromosome 19. HLA-DQ2homozygosity is associated with complications of CD such as refractory celiac disease type II (RCD II) and enteropathy-associated T-cell lymphoma(EATL). We investigated whether MYO9B also predisposes to RCD II and EATL. Methods: Genotyping of MYO9B and molecular HLA-DQ2typing were performed on 62 RCD II and EATL patients, 421 uncomplicated CD patients, and 1624 controls. Results: One single nucleotide polymorphismin MYO9B showed a significantly different allele distribution in RCD II and EATL patients compared with controls ( P = .00002). The rs7259292 T allele was significantly more frequent in RCD II and EATL patients compared with CD patients ( P = .0003; odds ratio [OR], 3.61; 95% confidence interval [CI], 1.78–7.31). The frequency of the haplotype carrying the T allele of this single nucleotide polymorphismwas significantly increased in RCD II and EATL patients (11%), compared with controls (2%) and CD patients (3%) (OR, 6.76; 95% CI, 3.40–13.46; P = 2.27E-09 and OR, 4.22; 95% CI, 1.95–9.11; P = .0001, respectively). Both MYO9B rs7259292 and HLA-DQ2homozygosity increase the risk for RCD II and EATL to a similar extent when compared with uncomplicated CD patients (OR, 4.3; 95% CI, 1.9–9.8 and OR, 5.4; 95% CI, 3.0–9.6, respectively), but there was no evidence for any interaction between these 2 risk factors. Conclusions: We show that both MYO9B and HLA-DQ2homozygosity might be involved in the prognosis of CD and the chance of developing RCD II and EATL.