Severe Cutaneous Adverse Reactions

Severe cutaneous adverse reactions (SCARs) are generally induced by drugs and encompass the conditions of Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN), drug induced eosinophilia and systemic syndrome (DRESS) also known as drug induced hypersensitivity syndrome (DIHS), and acute generalized exanthematous pustulosis (AGEP). These conditions, although rare, cause significant morbidity and are potentially fa‐ tal. It is therefore important for the treating physician to promptly recognize SCARs through the identification of their characteristic clinical features so that the offending drug is promptly withdrawn and supportive and adjunctive therapies are administered. SCARs are accompanied by particular abnormalities on routine laboratory investigations and skin biop‐ sy that enables confirmation of the diagnosis and provision of useful prognostic informa‐ tion. Data bases have been established, predominantly in Europe, since the 1980s to characterize the epidemiology of SCARs including the identification of drugs with the high‐ est relative risk and the latency between the commencement of drug intake and the onset of clinical manifestations. The pathogenesis of the various SCARs involves delayed T cellmediated inflammation in a genetically predisposed individual and in the case of DIHS, may involve viral factors. The emerging field of the genetic susceptibility to SCARs has raised the important issue of pharmacogenetic screening as a method of predicting an indi‐ vidual’s risk of developing SCAR to a certain drug. The treatment of SJS/TEN is dependent on supportive care in a suitable settling such as a Burns Unit and the role of immunomodu‐ latory agents is not well defined and is not robustly supported in the literature by prospec‐ tive studies. The evidence for the use of immunomodulatory agents and ganciclovir is emerging in the treatment of DIHS/DRESS. AGEP usually has favourable prognosis if the offending drug is withdrawn but a course of corticosteroids may hasten recovery.