Aetiopathogenesis of severe cutaneous adverse reactions (SCARs) in children: A 9-year experience in a tertiary care paediatric hospital setting.

BACKGROUND: Severe cutaneous adverse reactions (SCARs) are delayed-type hypersensitivity reactions to drugs including as follows: Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS), Stevens-Johnson syndrome (SJS), Toxic Epidermal Necrolysis (TEN) and Acute Generalized Exanthematous Pustulosis (AGEP). Incidence, triggers and management of SCARs have not been investigated in large-scale epidemiological studies on children. OBJECTIVE: The aim of our study was to collect epidemiological, clinical and aetiological data from children with SCARs referred to our tertiary care paediatric hospital of Florence. METHODS: From 2010 to 2018 charts of children with diagnosis of SCAR were reviewed, and data collected during the acute phase and/or the subsequent allergy evaluation. Patients underwent patch tests, intradermal tests and lymphocyte transformation tests. All children were investigated for infectious diseases. RESULTS: Incidence of SCARs in hospitalized children was 0.32% over a 9-year period. Fifty-four children were enrolled (31 M; 23 F; median age 6.5 years): 17 cases of DRESS, 30 SJS, 3 TEN, 2 AGEP, 1 linear immunoglobulin A bullous disease (LABD) and 1 pemphigus. Twenty-eight out of 54 patients underwent drug allergy investigations, and 50% of them resulted positive. Combining clinical history and results of allergy work-up, 74% SCARs seem to be caused by drugs, 18.6% by both drugs and infections, 3.7% by infections, and 3.7% remained idiopathic. No deaths occurred. CONCLUSIONS: In this study, SCARs incidence is in line with literature data. Drugs were most commonly the leading cause. Management of SCARs requires cooperation among professional figures for an early diagnosis and a prompt treatment. Mortality rate seems to be lower in children.

Linear IgA bullous dermatosis associated with ulcerative colitis: A case report and literature review.

We report the case of a 59-year-old Japanese woman who developed linear IgA bullous dermatosis during treatment for ulcerative colitis that manifested as pruritic vesicles with erythema on the trunk and scalp. Histopathological examination revealed subepidermal bulla with neutrophil and eosinophil infiltration in the upper dermis. Direct immunofluorescence revealed linear IgA deposits at the basement membrane zone, and indirect immunofluorescence using split skin revealed IgA reaction to the epidermal side (lamina lucida type). We reviewed 33 reported cases of linear IgA bullous dermatosis associated with ulcerative colitis and found that ulcerative colitis preceded the onset of linear IgA bullous dermatosis in 94% of the patients and that IgA-positive patients in split skin indirect immunofluorescence all showed the lamina lucida type, indicating that target antigens for serum IgA antibodies may reside in the lamina lucida. Regarding the pathogenetic association of ulcerative colitis and linear IgA bullous dermatosis, intestinal inflammation may induce the exposure and presentation of intestinal antigens that are cross-reactive to cutaneous antigens, stimulating autoimmune response to antigens of cutaneous basement membrane zones.

C-Terminal Processing of Collagen XVII Induces Neoepitopes for Linear IgA Dermatosis Autoantibodies.

Transmembrane collagen XVII (COL17) is a hemidesmosomal component of basal keratinocytes that can be targeted by autoantibodies in autoimmune blistering disorders, including linear IgA dermatosis (LAD). COL17 can be physiologically cleaved within the juxtamembranous extracellular NC16A domain, and LAD autoantibodies preferentially react with the processed ectodomains, indicating that the processing induces neoepitopes. However, the details of how neoepitopes develop have not been elucidated. In this study, we show that C-terminal processing of COL17 also plays a role in inducing neoepitopes for LAD autoantibodies. First, the mAb hC17-ect15 targeting the 15th collagenous domain of COL17 was produced, which showed characteristics similar to LAD autoantibodies. The mAbs preferentially reacted with C-terminally deleted (up to 682 amino acids) recombinant COL17, suggesting that C-terminal processing shows neoepitopes on the 15th collagenous domain. The LAD autoantibodies also react with C-terminal deleted COL17. Therefore, neoepitopes for LAD autoantibodies also develop after C-terminal processing. Finally, the passive transfer of the mAb hC17-ect15 into human COL17-expressing transgenic mice failed to induce blistering disease, suggesting that neoepitope-targeting antibodies are not always pathogenic. In summary, this study shows that C-terminal processing induces dynamic structural changes and neoepitopes for LAD autoantibodies on COL17.