The DRB1*03∶01 allele, and consequently, DRB1*03∶01 haplotypes, have been associated to numerous immune-mediated disorders, as type 1 diabetes, multiple sclerosis or selective IgA deficiency, among many others; in some cases with the different DRB1*03∶01 haplotypes showing a differential contribution to disease risk [2], [3]. Here, HLA-DRB1 is linked to selective IgA deficiency disease.