Homozygosity for HLA-DRB1*09:01 was found to confer a higher risk of MCTD than heterozygosity (*09:01/not *09:01: P = 0.0666, OR 1.55, 95% CI 0.98‒2.44; *09:01/*09:01: P = 0.1523, OR 2.15, 95% CI 0.83‒5.58). Here, HLA-DRB1 is linked to mixed connective tissue disease.