Wichittra TassaneeyakulNapat PrabmeechaiChonlaphat SukasemThachanan KongpanParinya KonyoungPansu ChumworathayiSomsak TiamkaoUsanee KhunarkornsiriKongkiat KulkantrakornNiwat SaksitNontaya NakkamPatompong SatapornpongSuda VannaprasahtAlisara SangviroonSurakameth MahasirimongkolNuanjun WichukchindaTicha RerkpattanapipatWongwiwat TassaneeyakulKhon Kaen UniversityFaculty of MedicineIntegrated Epilepsy Research GroupDivision of Pharmacogenomics and Personalized MedicineSomdech Phra Debaratana Medical Center (SDMC)Mahidol UniversityPolice General HospitalUdonthani HospitalFaculty of Medicine, Thammasat UniversityThailand Ministry of Public Health2018-12-112019-03-142018-12-112019-03-142016-01-01Pharmacogenetics and Genomics. Vol.26, No.5 (2016), 225-23417446880174468722-s2.0-84959257971https://repository.li.mahidol.ac.th/handle/20.500.14594/43229© 2016 Wolters Kluwer Health, Inc. All rights reserved. Background Phenytoin is one of the most common causative drugs of several types of severe cutaneous adverse reactions (SCAR) such as Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and drug reactions with eosinophilia and systemic symptoms (DRESS). Genetic polymorphisms of the human leukocyte antigens (HLA) and cytochromes P450 (CYP) have been proposed as key elements for the susceptibility to phenytoin-related SCAR in certain ethnicities. This study investigated the associations between the genetic polymorphisms of HLA class I and CYP2C9 and phenytoin-related SCAR in a Thai population. Materials and methods Sixty phenytoin-related SCAR (i.e. 39 SJS/TEN and 21 DRESS) and 92 phenytoin-tolerant patients were enrolled in the study. The genotypes of HLA class I and CYP2C9 were determined. Results Six HLA alleles including HLA-A∗33:03, HLAB∗c 38:02, HLA-B∗51:01, HLA-B∗56:02, HLA-B∗c58:01, and HLA-C∗14:02 were significantly associated with phenytoinrelated SJS/TEN, whereas only the HLA-B∗51:01 was significantly associated with phenytoin-related DRESS. The odds ratios of phenytoin-related SJS/TEN in the patients who carried one of these alleles ranged from 4-to 10-fold. The frequencies of patients who carried the HLA-B∗15:02 in the SJS/TEN (12.82%) or the DRESS (9.52%) groups were not significantly different from that of the controls (14.13%). The higher risk of phenytoin-related SJS/TEN was observed in the patients with CYP2C9∗3 (odds ratio=4.30, 95% confidence interval=1.41-13.09, P<0.05). Conclusion Neither SJS/TEN nor DRESS caused by phenytoin was significantly associated with the HLAB∗ 15:02. The CYP2C9∗3 variant was significantly associated with phenytoin-related SJS/TEN, but not DRESS. Certain alleles of HLA, particularly HLA-B∗56:02, were significantly associated with phenytoin-related SCAR in the study population.Mahidol UniversityBiochemistry, Genetics and Molecular BiologyArticleSCOPUS10.1097/FPC.0000000000000211