ERAP1 and ankylosing spondylitis: The genetic model implemented in our study along with the odds ratios effect sizes for disease risk and the genotype penetrance table were inspired from the suspected pure biological epistatic effect between ERAP1 and HLA-B*27 in Ankylosing Spondylitis affecting the general population with British ancestry with a prevalence of ∼ 1% [33, 36].