Diplotype frequencies of HLA-DRB1*04:01-DQB1*03:01/DRB1*15:01-DQB1*06:02, DRB1*15:02-DQB1*06:01 (P = 9.13 × 10–7, OR 73.08, 95% CI 4.22‒1265.70), DRB1*09:01-DQB1*03:03/DRB1*15:01-DQB1*06:02, DRB1*15:02-DQB1*06:01 (P = 0.0281, OR 2.60, 95% CI 1.17‒5.77) were also higher in MCTD patients than in controls. The gene discussed is HLA-DRB1; the disease is mixed connective tissue disease.