In addition, unlike the cases of HLA-B*57:01 in abacavir HSRs [11] and HLA-B*58:01 in allopurinol-induced Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) [12], multiple class I and class II HLA alleles, which have variable distribution and risk across ethnic groups, have been associated with nevirapine HSRs [6,13,14]. This evidence concerns the gene HLA-B and toxic epidermal necrolysis.