Epidemiology and Risk Factors for Severe Delayed Drug Hypersensitivity Reactions

Severe delayed drug hypersensitivity reactions comprise different clinical entities and can involve different immune-mediated mechanisms. Common examples are severe cutaneous adverse reactions and druginduced internal organ injuries. The incidence of such reactions is overall low but seems to be on the rise reaching numbers as high as 9 per million individuals-years in the case of SJS/TEN and DRESS. Such conditions carry an important associated morbidity, and mortality can attain 40% in SJS/TEN patients, making these hypersensitivity reactions important targets when implementing preventive measures. Several risk factors have been identified for reaction severity; some are transverse, such as older age and underlying chronic diseases. The recent advances in pharmacogenetics allowed the identification of specific populations with higher risk and permitted strategic avoidance of certain drugs being HLA-B*57:01 screening in patients initiating abacavir the best successful example. In this work, we reviewed the epidemiology of SCARs and liver/kidney/lung drug-induced immune-mediated reactions. We focus on particular aspects such as prevalence and incidence, drugs involved, mortality and risk factors.