HLA-DRB1 and mixed connective tissue disease: No deviation from the Hardy–Weinberg equilibrium was observed in the controls (HLA-DRB1: P = 0.4257; DQB1: P = 0.2162), but deviation was found in the MCTD patients (DRB1: P = 0.0130; DQB1: P = 0.2714).