A case–control study was performed at the Laboratory for Pharmacogenomics, Somdech Phra Debaratana Medical Center (SDMC), Ramathibodi Hospital, Thailand. Fifteen LTG-induced CADR (4 cases of SJS, 1 case of DRESS, and 10 cases of MPE) were recruited from the Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Manarom Hospital, and Srinagarind Hospital between 2011 and 2015. All patients who developed CADR, as SJS, MPE, or DRESS, within 2 months after initiating LTG treatment were recruited for the study. The dermatological diagnosis was made by a dermatologist or allergist who reviewed photographs, pathological slides, clinical morphology, and medical records. MPE was defined as the presence of erythematous macules and papules without mucosal involvement, and in which the skin rash resolved after the drug was discontinued. The RegiSCAR criteria were used to establish SJS and DRESS. SJS was defined as skin detachment of BSA <10%, and TEN as skin detachment of BSA >30%. DRESS was defined as presenting with fever, maculopapular rash with internal organ involvement, and hematologic abnormalities. Patients who had been taking LTG for more than 6 months without evidence of cutaneous adverse effects were recruited as LTG-tolerant controls. In addition, the general population who had not taken LTG and had no history of drug-induced CADR were included in this study. Both case and control subjects were independently recruited with no family relationship. Data for this general control group were obtained from 369 and 986 subjects undergoing HLA-A and -B genotyping, respectively.