HLA-B*51:01 and CYP2C9*3 Are Risk Factors for Phenytoin-Induced Eruption in the Japanese Population: Analysis of Data from the Biobank Japan Project

CYP2C9*3 and HLA‐B alleles are reportedly associated with phenytoin‐induced eruption in some East Asian populations; however, this finding is not readily applicable to the Japanese population. Thus, we aimed to investigate the risk alleles using samples and data from BioBank Japan. A total of 747 patients (24 cases and 723 tolerant controls) were selected for analysis. Case‐control association studies were conducted, using CYP2C9*3, CYP2C9*27, CYP2C19*2, CYP2C19*3, and HLA‐B allele genotype data. CYP2C9*3 carrier status was significantly associated with phenytoin‐induced eruption (P = 0.0022, odds ratio 7.05, 95% confidence interval, 2.44–20.4). HLA‐B*51:01 showed the most prominent association (P = 0.010, odds ratio 3.19, 95% confidence interval, 1.37–7.48). Including both of these features improved predictive performance, measured as area under the receiver operating characteristic curve, by 10%. CYP2C9*3 and HLA‐B*51:01 allele carrier statuses are significantly associated with phenytoin‐induced eruption; thus, checking this carrier status before prescription would decrease the incidence of phenytoin‐induced eruption in clinical practice.