HLA-DRB1 and urticaria: The patient with an FDR presented here had HLA-A30 B13 Cw6, HLA-B*13, and HLA DRB1*13-DQB1*06 haplotypes, which make her susceptible to an FDR induced by trimethoprim/sulfamethoxazole and dapsone, as well as to aspirin-induced urticaria, respectively [18,19,20,21].