Human leukocyte antigen genotyping of 272 Malawian HIV patients receiving nevirapine-containing regimens (of whom 117 had nevirapine hypersensitivity) has shown that HLA-C*04:01 increases the risk of Stevens-Johnson syndrome/toxic epidermal necrolysis, with an odds ratio of 5.17 (95% confidence interval, 2.39–11.18). This evidence concerns the gene HLA-C and toxic epidermal necrolysis.