In addition to the classic iDILI classification, which includes cases that do not present autoimmune features [1,2,4,5,6,7,8,9,10], the RUCAM helps characterize several iDILI subtypes, like those with genetic features of human leukocyte antigens (HLAs) [11,12,13,14], the immune system-related Stevens–Johnson syndrome, or toxic epidermal necrolysis (TEN) [15,16,17,18], as well as autoimmune findings related to cytochrome P450 (CYP) in the form of serum anti-CYP antibodies [19,20,21]. The gene discussed is HLA-S; the disease is toxic epidermal necrolysis.