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It is known that rare but severe cutaneous adverse drug reactions (cADRs), such as Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN) and drug-induced hypersensitivity syndrome (DIHS), are induced by carbamazepine (CBZ). Recent studies have shown an association between HLA-A*31:01 and CBZ-induced severe cADRs in Japanese and Caucasian populations. In this study, we developed a simple method to detect the HLA-A*31:01 allele by nested allele-specific primer-polymerase chain reaction combined with restriction fragment length polymorphism analysis. Accuracy of the developed method was evaluated by direct sequencing analysis of PCR products amplified from DNA samples with known HLA-A genotypes and by consigning diagnosis of DNA samples with unknown HLA-A genotypes to a company providing clinical laboratory testing. The method developed in this study is simple, rapid, and of low cost compared to outsourcing tests and may be useful for in-house testing of the HLA-A*31:01 allele.

In some adverse drug reactions (ADRs), genetic predisposition plays a significant role in pathogenesis, and the skin is the most frequently reported target. These severe cutaneous ADRs include bullous fixed drug eruptions (FDE), acute generalized exanthematous pustulosis (AGEP), drug-induced hypersensitivity syndrome (HSS), Stevens-Johnson syndrome (SJS), and toxic epidermal necrolysis (TEN). The putative contribution of individual effector cells in drug hypersensitivity is briefly mentioned. To trigger these drug hypersensitivities, certain class I HLA alleles (e.g., HLA-A and HLA-B alleles) and certain class II HLA alleles (e.g., HLA-DR alleles) have been recently found to be the genetic determinants. One of the best characterized examples mentioned in this article is HLA-B*1502 to determine the incidence of carbamazepine-induced SJS. How drugs are processed and presented by these HLA alleles to activate immune responses has been explained by several hypotheses. Further implication of pharmagenomic findings to prevent drug-induced severe skin reactions can be achieved by pre-screening putative risk HLA alleles before using drugs.