Perhaps one of the most characteristic and noteworthy examples of success story in pharmacogenomics is the discovery of the association of the HLA-B*1502 allele with the devastating carbamazepine-induced Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis (SJS/TEN) [5] and of the HLA-B*5801 allele with allopurinol-induced severe cutaneous adverse reactions [6] in Southeast Asia and particularly in Taiwan. This evidence concerns the gene HLA-B and Stevens-Johnson syndrome.