Drug-induced Stevens Johnson syndrome and toxic epidermal necrolysis: Interpreting the systematic reviews on immunomodulatory therapies

Drug-induced Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are non-immunoglobulin E-mediated severe cutaneous adverse reactions with a high risk of morbidity, mortality, and physical and mental health impact. These are associated with certain high-risk drugs, human leukocyte antigen (HLA)-specific genotypes and ethnicities. HLA class I-restricted oligoclonal CD8 cytotoxic T-cell responses occur at the tissue level in SJS/TEN. Cytotoxic T cells are the T effector cells that result in keratinocyte apoptosis (cell death) mediated by T effector molecules granzyme B, perforin, granulysin, gamma interferon, tumor necrosis factor-alpha, and lipocalin-2. The clinical hallmarks of SJS/TEN include fever, ≥2 mucosal involvements (ocular, oral, and genital), and positive Nikolsky sign with epidermal detachment. Systematic reviews on immunomodulatory treatments remain limited by the paucity of randomized controlled trials, heterogeneity of studies, and non-standardization of outcome measures. Preventive HLA genotype screening before the prescription of carbamazepine and allopurinol may further reduce the incidence of SJS/TEN. The role of immunomodulatory treatments in SJS/TEN is at present not supported by robust evidence from systematic reviews given the lack of randomized controlled trials. The evidence for improved survival with off-label use of corticosteroids plus intravenous immunoglobulins, ciclosporin plus intravenous immunoglobulins, and ciclosporin alone has not been demonstrated by network meta-analyses and meta-regression. In the real-world clinical setting, systemic corticosteroids (in SJS and overlap SJS/TEN), ciclosporin, and etanercept (in TEN) appear to be the off-label treatments currently most widely used.