HLA-DRB1 and Achalasia: We detected only a slight increase in the frequency of the Caucasian European haplotype HLA-A*29:02-B*44:03-C*16:01-DRB1*07:01-DQB1*02:02 in achalasia patients (pC = 0.02, OR = 9.32; 95% CI = 1.76–65.52).