expressing the NAT2*6A and NAT2*7 variants have an increased risk for developing DRESS syndrome-like reactions to this anti-inflammatory drug. None-genetic ADME factors are also associated with increased risks of developing the DRESS syndrome. Allopurinol is metabolized to oxipurinol, a product with a far slower renal excretion rate than its parent compound. Renal impairment is associated with abnormally high blood levels of oxipurinol and an increased risk of developing the DRESS syndrome, particularly the more severe forms of this disorder. Dysfunction of the kidney and liver are also suggested to promote this disorder in response to other drugs due to the accumulation of SCARs-inducing drugs or metabolites in blood and tissues. Currently, it is suspected that the expression of particular HLA proteins and T-cell receptors interact with ADME factors to promote SCARs particularly in their more serious forms. Viral reactivation During the progression of the DRESS syndrome certain viruses that previously infected an individual and then became latent are reactivated and proliferate. Viruses known to do so include certain members of the Herpesviridae family of Herpes viruses viz., Epstein–Barr virus, human herpesvirus 6, human herpesvirus 7, and cytomegalovirus. Individuals with DRESS syndrome may exhibit sequential reactivation of these four viruses, typically in the order just given. Reactivation of these viruses is associated with a flare-up in symptoms, a prolonged course, and increased disease severity which includes significant organ involvement and the development of certain autoimmune diseases viz., systemic lupus erythematosus, autoimmune thyroiditis, and type 1 diabetes mellitus. While these viral reactivations, particularly of human herpes virus 6, have been suggested to be an important factor in the pathogenesis of the DRESS syndrome, studies to date have not clearly determined if they are a cause or merely a consequence of T cell-mediated tissue injury. Preventative Currently, screening individuals for the expression of certain HLA alleles before initiating treatment of patients with DRESS-inducing drugs is recommended. These recommendations typically apply only to specific populations that have a significant chance of expressing the indicated allele since screening of populations with extremely low incidences of expressing an allele is considered cost-ineffective. Individuals expressing the HLA allele associated with sensitivity to an indicated drug should not be treated with the drug. These recommendations include: Allopurinol: The American College of Rheumatology guidelines for the management of gout recommend HLA-B*58:01 screening before allopurinol treatment. This is provided in many medical centers in Taiwan, Hong Kong, Thailand, and Mainland