HLA-DQB1 and Achalasia: Furthermore, it has been demonstrated in 1,068 cases of achalasia from central Europe, Spain, and Italy that an eight-residue insertion at position 227–234 in the cytoplasmic tail of HLA-DQβ1 (encoded by HLA-DQB1∗05:03 and HLA-DQB1∗06:01) confers the strongest risk for achalasia.