There are hundreds of polymorphisms of HLA-DRB1 which have been associated with different autoimmune disorders as well as with immune response to infection and vaccines The association between HLA-DRB1*11 and autoimmune, infectious and cancer diseases has been previously reported for: systemic sclerosis, Henoch-Schönlein purpura, systemic juvenile idiopathic arthritis, Helicobacter pylori-positive idiopathic thrombocytopenic purpura, hairy cell leukaemia, cervical cancer, among others [44–49]. This evidence concerns the gene HLA-DRB1 and thrombocytopenic purpura.