Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis

Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are severe cutaneous adverse drug reactions (SCARs). The most common causative drugs of SJS/TEN are allopurinol, carbamazepine, abacavir, phenytoin, and lamotrigine. SJS/TEN are categorized based on the percentage of epidermal detachment area: (i) SJS: less than 10%, (ii) TEN: greater than 30%, (iii) and overlapping SJS/TEN: 10–30%. The pathogenesis of SJS/TEN is not fully understood, but some immunological and genetic factors are believed to be involved. There is a strong association between some specific HLA haplotypes and drug-induced SJS/TEN, for example, HLA-B*15:02 and carbamazepine-, HLA-B*58:01 and allopurinol. CD8+ cytotoxic T cells and natural killer (NK) cells play an important role in the pathogenesis of SJS/TEN, and upon the activation, they produce cytokines, chemokines, and cytotoxic proteins, that cause extensive keratinocytes apoptosis. Systemic corticosteroid and cyclosporine are still used as the first line in the treatment of SJS/TEN, in combination with care support.