Epidermal necrolysis (EN) encompasses Stevens-Johnson syndrome (SJS, < 10% of the skin affected), Lyell syndrome (toxic epidermal necrolysis, TEN, with ≥30% of the skin affected) and an overlap syndrome (10 to 29% of the skin affected). These rare diseases are caused, in 85% of cases, by pharmacological treatments, with symptoms occurring 4 to 28 days after treatment initiation. Mortality is 20 to 25% during the acute phase, and almost all patients display disabling sequelae (mostly ocular impairment and psychological distress).The objective of this French national diagnosis and care protocol (protocole national de diagnostic et de soins; PNDS), based on a critical literature review and on a multidisciplinary expert consensus, is to provide health professionals with an explanation of the optimal management and care of patients with EN. This PNDS, written by the French National Reference Center for Toxic Bullous Dermatoses was updated in 2017 (https://www.has-sante.fr/portail/jcms/c_1012735/fr/necrolyse-epidermique-syndromes-de-stevens-johnson-et-de-lyell). The cornerstone of the management of these patients during the acute phase is an immediate withdrawal of the responsible drug, patient management in a dermatology department, intensive care or burn units used to dealing with this disease, supportive care and close monitoring, the prevention and treatment of infections, and a multidisciplinary approach to sequelae. Based on published data, it is not currently possible to recommend any specific immunomodulatory treatment. Only the culprit drug and chemically similar molecules must be lifelong contraindicated.

AIMSLinear immunoglobin A (IgA) bullous dermatosis is a rare autoimmune dermatosis considered spontaneous or drug-induced (DILAD). We assessed all DILAD cases, determined the imputability score of drugs and highlighted suspected drugs. METHODSData for patients with DILAD were collected retrospectively from the French Pharmacovigilance network (from 1985 to 2017) and from physicians involved in the Bullous Diseases French Study Group and the French Investigators for Skin Adverse Reactions to Drugs. Drug causality was systematically determined by the French imputability method. RESULTSOf the 69 patients, 42% had mucous membrane involvement, 20% lesions mimicking toxic epidermal necrolysis (TEN), 21% eosinophil infiltrates and 10% keratinocytes necrosis. Direct immunofluorescence, in 80%, showed isolated linear IgA deposits. Vancomycin (VCM) was suspected in 39 cases (57%), 11 had TEN-like lesions, as compared with three without VCM suspected. Among the 33 patients with a single suspected drug, 85% had an intrinsic imputability score of I4. Among them, enoxaparin, minocycline and vibramycin were previously unpublished. For all patients, the suspect drug was withdrawn; 15 did not receive any treatment. First-line therapy for 31 patients was topical steroids. Among the 60 patients with British Journal of Clinical Pharmacology Br J Clin Pharmacol (2019) 85 570-579 570 available follow-up, 52 achieved remission, 10 without treatment. Four patients experienced relapse, four died and five had positive accidental rechallenges. CONCLUSIONSThere is no major clinical difference between DILAD and idiopathic linear IgA bullous dermatosis, but the former features a higher prevalence of patients mimicking TEN. VCM, suspected in more than half of the cases, might be responsible for more severe clinical presentations. We report three new putative drugs. WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT• Linear IgA bullous dermatosis (LABD) is a rare autoimmune dermatosis that may be spontaneous or drug induced.• Vancomycin (VCM) is the most frequent putative drug.• Drug-induced LABD (DILAD) may be more severe than idiopathic LABD, mimicking toxic epidermal necrolysis with Nikolsky sign and large erosions WHAT THIS STUDY ADDS• In this large series of DILAD, we systematically assessed the imputability of suspect drugs. Most of them are antibiotics with VCM as the most frequent. Eighty percent of suspect drugs had a high causality score. Three drugs had never been reported to induce DILAD before (enoxaparin, minocyclin, vibramycin). • Twenty percent of cases (especially those induced by VCM) mimicked toxic epidermal necrolysis. Data collectionFor each case, data collected from pharmacovigilance or medical files included epidemiological and clinical characteristics Drug-induced linear immunoglobulin A bullous dermatosis Br J Clin Pharmacol (2019) 85 570-579 571 Drug-induced linear immunoglobulin A bullous dermatosis Br J Clin Pharmacol (2019) 85 570-579 579

Epidermal changes are indicative for the severity of DRESS.

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Toxic epidermal necrolysis (TEN) is a life-threatening cutaneous adverse drug reaction. To better understand why skin symptoms are so severe, we conducted a prospective immunophenotyping study on skin and blood. Mass cytometry results confirmed that effector memory polycytotoxic CD8+ T cells (CTLs) are the main leucocytes in TEN blisters at the acute phase. Deep T cell receptor (TCR) repertoire sequencing identified massive expansion of unique CDR3 clonotypes in blister cells. The same clones were highly expanded in patient’s blood, and the degree of their expansion showed significant correlation with disease severity. By transducing α and β chains of the expanded clonotypes into a TCR-defective cell line, we confirmed that those cells were drug specific. Collectively, these results suggest that the relative clonal expansion and phenotype of skin-recruited CTLs condition the clinical presentation of cutaneous adverse drug reactions.