The purpose of this study was to investigate the association of genetic factors including variants in HLA-B and CYP2C genes and non-genetic factors with phenotype-specific phenytoin (PHT)-induced severe cutaneous adverse reactions (SCARs) in Thai patients.
Thirty-six PHT-induced SCAR cases (15 Stevens-Johnson syndrome (SJS) and 21 drug rash with eosinophilia and systemic symptoms (DRESS)/drug hypersensitivity syndrome (DHS)) and 100 PHT-tolerant controls were studied. Variants in HLA-B, CYP2C9, and CYP2C19 genes were genotyped. Fisher's exact test and multiple logistic regression analysis were performed to test the association of genetic and non-genetic factors with specific type of SCARs.
Multiple logistic regression models showed that genetic and non-genetic factors associated with PHT-induced SCARs were specified to its phenotype. HLA-B*13:01, HLA-B*56:02/04, CYP2C19*3, and omeprazole co-medication were strong risk factors of DRESS/DHS (adjusted OR = 13.29, p = 0.0001; adjusted OR = 56.23, p = 0.0007; adjusted OR = 6.75, p = 0.0414; and adjusted OR = 9.21, p = 0.0020, respectively). While CYP2C9*3 and having Chinese ancestry were significant risk factors of SJS (adjusted OR = 10.41, p = 0.0042 and adjusted OR = 5.40, p = 0.0097, respectively). Combined genetic and non-genetic risk factors optimized sensitivity and increased specificity for predicting PHT-induced SCARs.
This study showed that distinct genetic markers were associated with phenotype-specific PHT-induced SCARs. Non-genetic factor, omeprazole co-medication, was strongly associated with PHT-induced DRESS/DHS in addition to variants in HLA-B and CYP2C genes. Combined markers may be better predictors for PHT-induced SCARs.