HLA-DRB1 and systemic sclerosis: This finding is interesting because this is a very uncommon antibody in Mexican admixed SSc patients (2% of Mexican SSc patients) [13], hence, the rarity of this allele (DRB1*04:04) and this antibody (anti-RNA polymerase III) in our dcSSc population support the theory of the influence of the immunogenetic background in the different clinical expression of the disease in populations from different ethnic groups.