Variants in human leukocyte antigen (HLA) genes have been associated with IM-ADRs [25], and some actionable HLA gene–drug interaction guidelines have been issued, including HLA-B*57:01 associated with hypersensitivity to abacavir, HLA-B*15:02 associated with carbamazepine-induced Steven-Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN), and HLA-B*58:01 associated with allopurinol-induced SJS/TEN [26]. This evidence concerns the gene HLA-B and Stevens-Johnson syndrome.