Abstract
Stevens–Johnson syndrome (SJS) and toxic epidermal necrolysis are severe cutaneous reactions that carry significant morbidity risks, and in more serious cases also mortality risks, for those affected. Overlap exists between SJS and toxic epidermal necrolysis, which most experts agree are part of the same disease spectrum. Both are most commonly precipitated by drugs and generally begin with a prodrome of high fever, sore throat and malaise, followed by the rapid onset of cutaneous blistering. Immune-mediated keratinocyte apoptosis or programmed cell death precedes the epidermal detachment that occurs in SJS and toxic epidermal necrolysis, although, by definition, it is more focal in SJS. Both conditions are also characterized by epidermal detachment in addition to mucosal involvement, although the development of large sheets of epidermal detachment in the absence of mucosal involvement is more characteristic of toxic epidermal necrolysis. However, the frequent presence of overlapping clinical features in a given patient often makes definitive classification difficult. According to the most recent consensus definition for the classification of SJS and toxic epidermal necrolysis, patients with total body surface area epidermal detachment of less than or equal to 10% are classified as SJS, more than 30% as toxic epidermal necrolysis and between 10 and 30% as SJS/toxic epidermal necrolysis overlap.