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Background: Acute generalized exanthematous pustulosis (AGEP) is a potentially severe adverse cutaneous drug reaction, which typically occurs within 24-48 hours after the intake of the culprit drug. Summary: AGEP is characterized by numerous sterile subcorneal pustules on erythematous skin and in less than a third of cases it can be associated with organ manifestations possibly leading to life-threatening symptoms (e.g. cholestasis, nephritis, lung and bone marrow involvement). In contrast to generalized pustular psoriasis (GPP) it can involve mucosal regions and typically resolves rapidly if the culprit drug is removed and adequate therapy with topical or systemic steroids administered. Diagnosis based on patient history, clinical signs and characteristic cutaneous histology is rarely challenging. Identification of the culprit drug may be aided by patch testing or lymphocyte transformation tests that are of limited value. Key Messages: Recent experimental data reviewed herein are supportive of an early role of drug-induced innate immune activation and innate cytokines such as interleukin (IL)-1, IL-36 and IL-17 in the pathogenesis of AGEP. This explains the rapid onset and neutrophilic character of the cutaneous inflammation, but also provide new avenues for in vitro tests aimed at better identifying the culprit drug. Lymphocyte transformation tests for Identification of the culprit drug are from limitied value.

Calciphylaxis and the arteriolosclerotic ulcer of Martorell (ASUM) represent two entities of cutaneous calcific arteriolopathies. Their differential diagnosis can be challenging, given similarities in their clinical and histological presentation. Calcification patterns have been proposed as a possible discriminative histological criterion, however, a systematic microstructural comparative analysis is lacking.The study aimed at a systematic comparative microstructural analysis of the calcification patterns in calciphylaxis versus ASUM.Skin biopsies of patients with leg ulcers due to calciphylaxis (20) and ASUM (69) diagnosed at three European wound care centres (Vienna, Bern, Zurich) were included. The extent of calcification, arteriolar calcification pattern and presence of extra-arteriolar calcification were assessed.All calciphylaxis and most ASUM patients (77%) presented with arteriolar calcification. Although the mean number of calcified vessels and the proportion of calcified area were significantly higher in calciphylaxis specimens (p = 0.003 and p = 0.0171), there was no significant difference in the pattern of arteriolar calcification (p = 0.177). Interestingly, extra-arteriolar calcification was detected in the majority of both calciphylaxis (93.3%) and ASUM samples (85.2%, p = 0.639). Notably, Alizarin Red S staining was superior to HE for the detection of calcifications of both entities (p = 0.014 and p 0.0001), and to von Kossa staining for ASUM samples (p = 0.0001). However, no differences could be observed between cases with uraemic and non-uraemic calciphylaxis or ulcerations located on the upper and lower leg.Our results indicate that extra-arteriolar calcification is not only present in calciphylaxis, but can also be detected in ASUM suggesting a lack of specificity for this finding. However, more specific calcification stains, such as Alizarin Red S, should be used in suspected cases, as calcifications may be overlooked using conventional HE staining.

Epidermal growth factor receptor (EGFR) and MEK inhibitors (EGFRi/MEKi) are beneficial for the treatment of solid cancers but are frequently associated with severe therapy-limiting acneiform skin toxicities. The underlying molecular mechanisms are poorly understood. Using gene expression profiling we identified IL-36γ and IL-8 as candidate drivers of EGFRi/MEKi skin toxicity. We provide molecular and translational evidence that EGFRi/MEKi in concert with the skin commensal bacterium Cutibacterium acnes act synergistically to induce IL-36γ in keratinocytes and subsequently IL-8, leading to cutaneous neutrophilia. IL-36γ expression was the combined result of C. acnes-induced NF-κB activation and EGFRi/MEKi-mediated expression of the transcription factor Kruppel-like factor 4 (KLF4), due to the presence of both NF-κB and KLF4 binding sites in the human IL-36γ gene promoter. EGFRi/MEKi increased KLF4 expression by blockade of the EGFR/MEK/ERK pathway. These results provide an insight into understanding the pathological mechanism of the acneiform skin toxicities induced by EGFRi/MEKi and identify IL-36γ and the transcription factor KLF4 as potential therapeutic targets.

Apremilast (Otezla®) is an oral small molecule phosphodiesterase 4 (PDE4) inhibitor approved for the treatment of psoriasis, psoriatic arthritis, and oral ulcers associated with Behçet’s disease. While PDE4 inhibition overall is mechanistically understood, the effect of apremilast on the innate immune response, particularly inflammasome activation, remains unknown. Here, we assessed the effect of apremilast in a psoriasis mouse model and primary human cells. Psoriatic lesion development in vivo was studied in K5.Stat3C transgenic mice treated with apremilast for 2 weeks, resulting in a moderate (2 mg/kg/day) to significant (6 mg/kg/day) resolution of inflamed plaques after 2-week treatment. Concomitantly, epidermal thickness dramatically decreased, the cutaneous immune cell infiltrate was reduced, and proinflammatory cytokines were significantly downregulated. Additionally, apremilast significantly inhibited lipopolysaccharide- or anti-CD3-induced expression of proinflammatory cytokines in peripheral mononuclear cells (PBMCs). Notably, inflammasome activation and secretion of IL-1β were not inhibited by apremilast in PBMCs and in human primary keratinocytes. Collectively, apremilast effectively alleviated the psoriatic phenotype of K5.Stat3 transgenic mice, further substantiating PDE4 inhibitor-efficiency in targeting key clinical, histopathological and inflammatory features of psoriasis. Despite lacking direct effect on inflammasome activation, reduced priming of inflammasome components upon apremilast treatment reflected the indirect benefit of PDE4 inhibition in reducing inflammation.

Acute generalized exanthematous pustulosis (AGEP) is a severe adverse cutaneous drug reaction. Although an involvement of drug-specific T cells has been reported, the physiopathology of AGEP and mechanism of neutrophilic skin inflammation remains incompletely understood. Recently, mutations in IL-36RN, the gene encoding the IL-36 receptor antagonist, have been reported to be more frequent in AGEP patients and pustular psoriasis. Here, we show that IL-36 cytokines, in particular IL-36γ, is highly expressed in lesional skin of AGEP patients, keratinocytes and macrophages being a major source of IL-36γ. Such an IL-36γ overexpression could not be observed in patients with drug-induced maculo-papular rash (MPR). In vitro, the causative drug specifically induced IL-36γ release either directly by peripheral blood monocytes from AGEP patients, or indirectly by keratinocytes in presence of autologous peripheral blood mononuclear cells. Such culprit drug induction of IL-36γ secretion in vitro was specific for AGEP and involved the sensing of drug/albumin complex as danger signal by Toll-like receptor 4. Our results suggest that IL-36γ secretion by monocytes/macrophages and keratinocytes in response to culprit drug exposure likely plays a key role in the pathogenesis of AGEP.

Autoinflammatory syndromes are a steadily growing group of inflammatory diseases caused by abnormal regulations of the innate immune system. The clinical presentation is multifaceted, but recurrent fever, skin involvement, joint inflammation and other systemic symptoms of inflammation are characteristic. In contrast to classic autoimmune diseases, autoantibodies or specific T cells are not involved in the pathogenesis. In fact, innate immunity plays the most important role in autoinflammation. While activation of the innate immune system is usually self-limiting in healthy individuals, mutations and dysregulation can lead to chronic and excessive activation of innate immune responses and to the development of autoinflammatory diseases.

Backgrounds Folate Hydrolase‐1 (FOLH1; PSMA) is a type II transmembrane protein, luminally expressed by solid tumour neo‐vasculature. Monoclonal antibody (mAb), J591, is a vehicle for mAb‐based brachytherapy in FOLH1+ cancers. Brachytherapy is a form of radiotherapy that involves placing a radioactive material a short distance from the target tissue (e.g., on the skin or internally); brachytherapy is commonly accomplished with the use of catheters, needles, metal seeds and antibody or small peptide conjugates. Herein, FOLH1 expression in primary (p) and metastatic (m) Merkel cell carcinoma (MCC) is characterized to determine its targeting potential for J591‐brachytherapy. Materials & Methods Paraffin sections from pMCC and mMCC were evaluated by immunohistochemistry for FOLH1. Monte Carlo simulation was performed using the physical properties of conjugated radioisotope lutetium‐177. Kaplan–Meier survival curves were calculated based on patient outcome data and FOLH1 expression. Results Eighty‐one MCC tumours were evaluated. 67% (54/81) of all cases, 77% (24/31) pMCC and 60% (30/50) mMCC tumours were FOLH1+. Monte Carlo simulation showed highly localized ionizing tracks of electrons emitted from the targeted neo‐vessel. 42% (34/81) of patients with FOLH1+/− MCC had available survival data for analysis. No significant differences in our limited data set were detected based on FOLH1 status (p = 0.4718; p = 0.6470), staining intensity score (p = 0.6966; p = 0.9841) or by grouping staining intensity scores (− and + vs. ++, +++, +++) (p = 0.8022; p = 0.8496) for MCC‐specific survival or recurrence free survival, respectively. Conclusions We report the first evidence of prevalent FOLH1 expression within MCC‐associated neo‐vessels, in 60‐77% of patients in a large MCC cohort. Given this data, and the need for alternatives to immune therapies it is appropriate to explore the safety and efficacy of FOLH1‐targeted brachytherapy for MCC. What's already known about this topic? We report the first evidence of prevalent folate hydrolase‐1 (FOLH1; also known as prostate‐specific membrane antigen) expression within MCC‐associated neovessels. What does this study add? Herein, FOLH1 expression in Merkel cell carcinoma neovasculature is validated, and the therapeutic mechanism of specific, systemic targeting of disseminated disease with antibody‐based brachytherapy, is defined.

Dermatofibrosarcoma protuberans (DFSP) is a rare, infiltrative, soft tissue tumor. It has a propensity for deep invasion but a low risk for distant metastasis. The classic presentation is a slowly progressive, painless, and erythematous to purpuric patch on the trunk or arms. A deep, subcutaneous punch biopsy or incisional biopsy should be performed for diagnosis in all suspected cases; wide undermining of the skin is to be avoided for minimizing the risk of tumor seeding and for retaining the feasibility of histopathologic examination of re-excisions. Histopathologic distinction of DFSP from dermatofibroma requires immunohistochemical assessment for CD34, factor XIIIa, nestin, apolipoprotein D, and cathepsin K. Management of this cutaneous sarcoma involves a multidisciplinary oncologic approach. Surgical excision is usually the first step in management. DFSP has a high propensity for local recurrence, even when surgical margins are negative; therefore, radiation therapy or rarely systemic therapy is recommended, especially for locally advanced or metastatic cases. The indolent nature of DFSP requires lifelong surveillance for recurrence; however, most recurrences occur within 3 years of the primary excision. The median time for the development of a local recurrence is estimated to be 32 months. An emerging theragnostic transmembrane receptor target, folate hydrolase-1 (FOLH1; prostate-specific membrane antigen), has been expressed in benign dermatofibromas and in high-grade sarcomatous phenotypes. These findings suggest that DFSP may also express FOLH1, which could allow for surveillance with FOLH1 PET/CT and antibody-mediated brachytherapy.

International audience; ImportanceNetherton syndrome (NS) is a rare, severe genetic disorder of cornification with high morbidity. Treatment for NS has been notoriously difficult. Recent studies showed an upregulated helper T cell (TH) 17/interleukin 23 (IL-23) pathway in NS, suggesting the possibility of treatment strategies that target IL-17.ObjectiveTo evaluate the clinical response of NS to treatment with the IL-17 antagonist secukinumab.Design, Setting, and ParticipantsThis case series study reports the experience of compassionate use therapy with secukinumab in 4 patients with severe NS, including 2 children, from December 1, 2018, to December 1, 2019, with 3 patients still undergoing treatment at the time of final analysis. Data were analyzed from December 1, 2018, to December 1, 2019.Main Outcomes and MeasuresExpression of IL-17 in the skin was evaluated by immunohistochemical analysis, and serum cytokine concentrations were measured using a commercially available assay. Treatment response was assessed using the Ichthyosis Area and Severity Index (IASI) total score, including measures of erythema and scaling, the Dermatology Life Quality Index (DLQI), and the 5-D itch scale.ResultsIn all 4 patients (age range, 9-27 years; 3 male and 1 female), immunostaining with an IL-17A antibody showed an increased number of positive cells in lesional skin. Cytokine assessment in serum samples revealed increased levels of CCL20. Treatment duration with secukinumab was 3 to 12 months at the time of this report. After 3 months of therapy, IASI scores were reduced by 44% to 88%, DLQI scores were reduced by 40% to 76%, and 5-D itch scale scores were reduced by 27% to 62%. This outcome was sustained at the 6-month follow-up. Two patients with an erythrodermic phenotype showed marked improvement of all parameters. A refractory palmoplantar eczematous eruption occurred in 2 patients, and a candidal nail infection developed in 2 patients. No severe adverse events were reported.Conclusions and RelevanceThis initial case series reporting the use of anti–IL-17 therapy in NS demonstrated marked cutaneous improvement, particularly in 2 pediatric patients with erythrodermic phenotypes. Further studies are needed to evaluate the long-term benefit of this potential treatment modality.

Background Acne vulgaris is a common dermatologic disease that causes significant social and psychological morbidity. Isotretinoin, as a vitamin A derivative, is the most effective agent in the treatment of acne. Evidence suggests that isotretinoin’s therapeutic function is independent of hormonal mediation; however, the effect of isotretinoin on serum androgens and precursor androgen levels in humans remains unclear. Objective Herein, we aim to investigate the effect of low-dose isotretinoin on androgen levels in women and postulate the role of concomitant anti-androgen therapy (e.g., spironolactone). Methods A total of 36 women, age 18 to 30 years, with moderate-to-severe nodulocystic acne were treated with 20 mg isotretinoin (Roaccutane) daily for 3 months. A hormone panel was obtained at baseline and after completion of the treatment course. The panel included dehydroepiandrosterone (DHEA), 17-hydroxyprogestrone, testosterone, free testosterone, dihydrotestosterone (DHT), luteinizing hormone, follicle stimulating hormone, and prolactin. Results Serum levels of testosterone (p = .015), prolactin (p = .001), and DHT (p = .001) were significantly decreased, while serum levels of DHEA (p = .001) significantly increased after isotretinoin treatment. No significant change was found in the other hormones evaluated. Limitations The distribution of acne was not assessed in our patient population. We did not directly evaluate for associations between elevated DHEA levels and clinical response rates. Conclusion Isotretinoin alone can decrease androgen levels, but increase an important driver of acne pathogenesis (i.e., DHEA). The co-administration of an anti-androgenic agent (e.g., spironolactone) may optimize the therapeutic efficacy of isotretinoin by limiting iatrogenic increases in DHEA and perhaps allow for more widespread use of low-dose isotretinoin.

Clinical differential diagnosis of arteriolosclerotic ulcers of Martorell is challenging due to the lack of clearly affirmative instrument-based diagnostic criteria. The aim of this study was to develop vascular histomorphological diagnostic criteria differentiating Martorell ulcers from other types of leg ulcers. The histomorphology of patients diagnosed with arteriolosclerotic ulcers of Martorell (n���=���67) was compared with that of patients with venous leg ulcers, necrotizing leukocytoclastic vasculitis, pyoderma gangrenosum, and non-ulcerative controls (n���=���15 each). In a multivariable logistic regression model, the rates of arteriolar calcification (odds ratio (OR) 42.71, 95% confidence interval (CI) 7.43-443.96, p���

In this study, we report the beneficial effects of a newly identified dermal cell subpopulation expressing the ATP-binding cassette subfamily B member 5 (ABCB5) for the therapy of nonhealing wounds. Local administration of dermal ABCB5+-derived mesenchymal stem cells (MSCs) attenuated macrophage-dominated inflammation and thereby accelerated healing of full-thickness excisional wounds in the iron-overload mouse model mimicking the nonhealing state of human venous leg ulcers. The observed beneficial effects were due to interleukin-1 receptor antagonist (IL-1RA) secreted by ABCB5+-derived MSCs, which dampened inflammation and shifted the prevalence of unrestrained proinflammatory M1 macrophages toward repair promoting anti-inflammatory M2 macrophages at the wound site. The beneficial anti-inflammatory effect of IL-1RA released from ABCB5+-derived MSCs on human wound macrophages was conserved in humanized NOD-scid IL2rγnull mice. In conclusion, human dermal ABCB5+ cells represent a novel, easily accessible, and marker-enriched source of MSCs, which holds substantial promise to successfully treat chronic nonhealing wounds in humans. Stem Cells 2019;37:1057–1074