Peeling Skin Disorders: A Paradigm for Skin Desquamation

Mature IL-36γ Induces Stratum Corneum Exfoliation in Generalized Pustular Psoriasis by Suppressing Corneodesmosin

Loss-of-function sequence variations in the IL36RN gene encoding IL-36 receptor antagonist cause familial generalized pustular psoriasis, which begins shortly after birth and is difficult to treat, and its effects on the epidermis are unclear. This study investigated the involvement of IL-36 receptor agonists in the epidermal formation of generalized pustular psoriasis. We found that the IL-36 receptor agonists, especially mature IL-36γ, stimulated IL-8 and pro-IL-36γ production in the epidermis while downregulating the genes encoding epidermal cornified envelope-related proteins, for example, corneodesmosin. IL-36 receptor antagonist and monoclonal anti-IL-36γ antibodies counteracted the effect of mature IL-36γ on corneodesmosin in keratinocytes in a dose-dependent manner. In the epidermis of patients with generalized pustular psoriasis with IL36RN loss-of-function sequence variations, pro-IL-36γ was overproduced in the epidermis, and corneodesmosin protein expression was markedly decreased in the region of giant subcorneal pustules (Kogoj's spongiform pustules), with high neutrophil infiltration. IL-8 induced by mature IL-36γ stimulated the infiltration of several neutrophils in the epidermis. The newly produced pro-IL-36γ is cleaved to the mature form by neutrophil proteases. This newly produced mature IL-36γ was predicted to further suppress the gene expression of corneodesmosin, leading to significant stratum corneum exfoliation and formation of the pustules. Overall, our results elucidate the mechanism underlying the formation of Kogoj's spongiform pustules in generalized pustular psoriasis.

Juvenile-onset Skin Fragility with Acral Blistering: A Quiz

Abstract is missing (Quiz)

Update on Chemical Peels

Chemical peeling is a procedure used for cosmetic improvement of the skin or treatment of some medical skin disorders, by the application of chemical exfoliant. In spite of a long history of clinical use of chemical peels, understanding of the science behind the procedure is still evolving. In this article, we review new concepts, understandings, and publications in the field of chemical peels.

Intrinsic Effects of Exposome in Atopic Dermatitis: Genomics, Epigenomics and Regulatory Layers

Atopic dermatitis (AD) or atopic eczema is an increasingly manifested inflammatory skin disorder of complex etiology which is modulated by both extrinsic and intrinsic factors. The exposome includes a person's lifetime exposures and their effects. We recently reviewed the extrinsic exposome's environmental risk factors that contribute to AD. The periods of pregnancy, infancy, and teenage years are recognized as crucial stages in the formation of AD, where the exposome leads to enduring impacts on the immune system. However, research is now focusing on the interactions between intrinsic pathways that are modulated by the extrinsic exposome, including genetic variation, epigenetic modifications, and signals, such as diet, stress, and microbiome interactions. As a result, immune dysregulation, barrier dysfunction, hormonal fluctuations, and skin microbiome dysbiosis are important factors contributing to AD development, and their in-depth understanding is crucial not only for AD treatment but also for similar inflammatory disorders.

The relationship of skin disorders, COVID-19, and the therapeutic potential of ginseng: a review

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has made significant impacts on global public health, including the development of several skin diseases that have arisen primarily as a result of the pandemic. Owing to the widespread expansion of coronavirus disease 19 (COVID-19), the development of effective treatments for these skin diseases is drawing attention as an important social issue. For many centuries, ginseng and its major active ingredients, ginsenosides and saponins, have been widely regarded as herbal medicines. Further, the anti-viral action of ginseng suggests its potential effectiveness as a therapeutic agent against COVID-19. Thus, the aim of this review was to examine the association of skin lesions with COVID-19 and the effect of ginseng as a therapeutic agent to treat skin diseases induced by COVID-19 infection. We classified COVID-19-related skin disorders into three categories: caused by inflammatory, immune, and complex (both inflammatory and immune) responses and evaluated the evidence for ginseng as a treatment for each category. This review offers comprehensive evidence on the improvement of skin disorders induced by SARS-CoV-2 infection using ginseng and its active constituents.

Acral peeling in Nagashima type palmo-plantar keratosis patients reveals the role of serine protease inhibitor B 7 in keratinocyte adhesion

Acral peeling skin syndrome (APSS) is a heterogenous group of genodermatoses, manifested by peeling of palmo-plantar skin and occasionally associated with erythema and epidermal thickening. A subset of APSS is caused by mutations in protease inhibitor encoding genes, resulting in unopposed protease activity and desmosomal degradation and/or mis-localization, leading to enhanced epidermal desquamation. We investigated two Arab-Muslim siblings with mild keratoderma and prominent APSS since infancy. Genetic analysis disclosed a homozygous mutation in SERPINB7, c.796C > T, which is the founder mutation in Nagashima type palmo-plantar keratosis (NPPK). Although not previously formally reported, APSS was found in other patients with NPPK. We hypothesized that loss of SERPINB7 function might contribute to the peeling phenotype through impairment of keratinocyte adhesion, similar to other protease inhibitor mutations that cause APSS. Mis-localization of desmosomal components was observed in a patient plantar biopsy compared with a biopsy from an age- and gender-matched healthy control. Silencing of SERPINB7 in normal human epidermal keratinocytes led to increased cell sheet fragmentation upon mechanical stress. Immunostaining showed reduced expression of desmoglein 1 and desmocollin 1. This study shows that in addition to stratum corneum perturbation, loss of SERPINB7 disrupts desmosomal components, which could lead to desquamation, manifested by skin peeling.

Experimental Models for the Study of Hereditary Cornification Defects

Ichthyoses comprise a broad spectrum of keratinization disorders due to hereditary defects of cornification. Until now, mutations in more than 50 genes, mostly coding for structural proteins involved in epidermal barrier formation, have been identified as causes for different types of these keratinization disorders. However, due to the high heterogeneity and difficulties in the establishment of valid experimental models, research in this field remains challenging and translation of novel findings to clinical practice is difficult. In this review, we provide an overview of existing models to study hereditary cornification defects with focus on ichthyoses and palmoplantar keratodermas.

The Whey Acidic Protein WFDC12 Is Specifically Expressed in Terminally Differentiated Keratinocytes and Regulates Epidermal Serine Protease Activity

WFDC proteins such as peptidase inhibitor 3 and SLPI inhibit proteases in the epidermis and other tissues. In this study, we tested the hypothesis that further WFDC protein family members might contribute to epidermal homeostasis. We found that in addition to peptidase inhibitor 3 and SLPI, WFDC5 and WFDC12 were expressed in human epidermis. In contrast to WFDC5, the expression of WFDC12 was induced during the late differentiation of keratinocytes and was restricted to the outermost layer of live cells. Single-cell RNA sequencing demonstrated that WFDC12-positive keratinocytes were characterized by the upregulation of LCE mRNA expression and downregulated the expression of keratins and claudins. Immunogold-electron microscopy revealed the colocalization of WFDC12 with corneodesmosomes in the lower stratum corneum. WFDC12 was elevated in the affected skin of patients with psoriasis, atopic dermatitis, and Darier disease. By contrast, WFDC12 expression was strongly upregulated not only in the affected but even more so in clinically normal-appearing skin of patients with Netherton syndrome. Finally, functional analysis showed distinct inhibitory activity of WFDC12 on neutrophil elastase and epidermal kallikrein‒related peptidase. Altogether, our study identified WFDC12 as a marker of the last stage of epidermal keratinocyte differentiation and suggests that WFDC12 contributes to the control of protease activity in the stratum corneum.

Genodermatoses with itch as a prominent feature

A number of inherited conditions cause chronic itch as a part of the recognized phenotype. Advances in the understanding of the genetic factors that cause these diseases elucidate the molecular underpinning of itch as a symptom. Our knowledge of the causes of chronic itch has also advanced, providing an opportunity to integrate the genetic pathophysiology with the molecular landscape of chronic itch mediators. This article reviews select genodermatoses that have itch as a predominant feature with a focus on the pathophysiology of the disease, how it may lead to itch and potential therapeutic targets.

Skin Barriers in Dermal Drug Delivery: Which Barriers Have to Be Overcome and How Can We Measure Them?

Although, drugs are required in the various skin compartments such as viable epidermis, dermis, or hair follicles, to efficiently treat skin diseases, drug delivery into and across the skin is still challenging. An improved understanding of skin barrier physiology is mandatory to optimize drug penetration and permeation. The various barriers of the skin have to be known in detail, which means methods are needed to measure their functionality and outside-in or inside-out passage of molecules through the various barriers. In this review, we summarize our current knowledge about mechanical barriers, i.e., stratum corneum and tight junctions, in interfollicular epidermis, hair follicles and glands. Furthermore, we discuss the barrier properties of the basement membrane and dermal blood vessels. Barrier alterations found in skin of patients with atopic dermatitis are described. Finally, we critically compare the up-to-date applicability of several physical, biochemical and microscopic methods such as transepidermal water loss, impedance spectroscopy, Raman spectroscopy, immunohistochemical stainings, optical coherence microscopy and multiphoton microscopy to distinctly address the different barriers and to measure permeation through these barriers in vitro and in vivo.

Serious analytical inconsistencies challenge the validity of the energy balance theory

Energy metabolism theory affirms that body weight stability is achieved as over time the average energy intake equals the average energy expenditure, a state known as energy balance. Here it is demonstrated, however, that weight stability coexists with a persistent energy imbalance. Such unexpected result emerges as a consequence of the answers to three fundamental problems: 1. Is it possible to model body weight fluctuations without the energy balance theory? And if so, what are the benefits over the energy balance strategy? 2. During energy balance, how the oxidized macronutrient distribution that underlies the average energy expenditure is related to the macronutrient distribution of the average energy intake? 3. Is energy balance possible under a low-fat diet that simultaneously satisfies the following conditions? (a) The fat fraction of the absorbed energy intake is always less than the oxidized fat fraction of the energy expenditure. (b) The carbohydrate fraction of the absorbed energy intake is always greater or equal to the oxidized carbohydrate fraction of the energy expenditure. The first of these issues is addressed with the axiomatic method while the rest are managed through analythical arguments. On the whole, this analysis identifies inconsistencies in the principle of energy balance. The axiomatic approach results also in a simple mass balance model that fits experimental data and explains body composition alterations. This model gives rise to a convincing argument that appears to elucidate the advantage of low-carbohydrate diets over isocaloric low-fat diets. It is concluded, according to the aforementioned model, that weight fluctuations are ultimately dependent on the difference between daily food mass intake and daily mass loss (e.g., excretion of macronutrient oxidation products) and not on energy imbalance. In effect, it is shown that assuming otherwise may caused unintended weight gain.

Loss-of-Function Variants in SERPINA12 Underlie Autosomal Recessive Palmoplantar Keratoderma

Inherited palmoplantar keratodermas refer to a large and heterogeneous group of conditions resulting from abnormal epidermal differentiation and featuring thickening of the skin of the palms and soles. Here, we aimed at delineating the genetic basis of an autosomal recessive form of palmoplantar keratodermas manifesting with erythematous hyperkeratotic plaques over the palms and soles, extending to non-palmoplantar areas. Whole-exome sequencing in affected individuals revealed homozygous nonsense variants in the SERPINA12 gene. SERPINA12 encodes the visceral adipose tissue-derived serpin A12, a serine protease inhibitor. The pathogenic variants were found to result in reduced visceral adipose tissue-derived serpin A12 expression in patients' skin biopsies in comparison to healthy controls. In addition, SERPINA12 downregulation in three-dimensional skin equivalents was associated with marked epidermal acanthosis and hyperkeratosis, replicating the human phenotype. Moreover, decreased SERPINA12 expression resulted in reduced visceral adipose tissue-derived serpin A12-mediated inhibition of kallikrein 7 activity as well as decreased levels of desmoglein-1 and corneodesmosin, two known kallikrein 7 substrates, which are required for normal epidermal differentiation. The present data, taken collectively, demarcate a unique type of autosomal recessive palmoplantar keratodermas, attribute to visceral adipose tissue-derived serpin A12 a role in skin biology, and emphasize the importance of mechanisms regulating proteolytic activity for normal epidermal differentiation.

Consensus reclassification of inherited epidermolysis bullosa and other disorders with skin fragility

BACKGROUND

Several new genes and clinical subtypes have been identified since the publication in 2014 of the report of the last International Consensus Meeting on Epidermolysis Bullosa (EB).

OBJECTIVES

We sought to reclassify disorders with skin fragility, with a focus on EB, based on new clinical and molecular data.

METHODS

This was a consensus expert review.

RESULTS

In this latest consensus report, we introduce the concept of genetic disorders with skin fragility, of which classical EB represents the prototype. Other disorders with skin fragility, where blisters are a minor part of the clinical picture or are not seen because skin cleavage is very superficial, are classified as separate categories. These include peeling skin disorders, erosive disorders, hyperkeratotic disorders, and connective tissue disorders with skin fragility. Because of the common manifestation of skin fragility, these 'EB-related' disorders should be considered under the EB umbrella in terms of medical and socioeconomic provision of care.

CONCLUSIONS

The proposed classification scheme should be of value both to clinicians and researchers, emphasizing both clinical and genetic features of EB. What is already known about this topic? Epidermolysis bullosa (EB) is a group of genetic disorders with skin blistering. The last updated recommendations on diagnosis and classification were published in 2014. What does this study add? We introduce the concept of genetic disorders with skin fragility, of which classical EB represents the prototype. Clinical and genetic aspects, genotype-phenotype correlations, disease-modifying factors and natural history of EB are reviewed. Other disorders with skin fragility, e.g. peeling skin disorders, erosive disorders, hyperkeratotic disorders, and connective tissue disorders with skin fragility are classified as separate categories; these 'EB-related' disorders should be considered under the EB umbrella in terms of medical and socioeconomic provision of care. Linked Comment: Pope. Br J Dermatol 2020; 183:603.

Molecular Mechanism of Epidermal Barrier Dysfunction as Primary Abnormalities

Epidermal barrier integrity could be influenced by various factors involved in epidermal cell differentiation and proliferation, cell–cell adhesion, and skin lipids. Dysfunction of this barrier can cause skin disorders, including eczema. Inversely, eczema can also damage the epidermal barrier. These interactions through vicious cycles make the mechanism complicated in connection with other mechanisms, particularly immunologic responses. In this article, the molecular mechanisms concerning epidermal barrier abnormalities are reviewed in terms of the following categories: epidermal calcium gradients, filaggrin, cornified envelopes, desquamation, and skin lipids. Mechanisms linked to ichthyoses, atopic dermatitis without exacerbation or lesion, and early time of experimental irritation were included. On the other hand, the mechanism associated with epidermal barrier abnormalities resulting from preceding skin disorders was excluded. The molecular mechanism involved in epidermal barrier dysfunction has been mostly episodic. Some mechanisms have been identified in cultured cells or animal models. Nonetheless, research into the relationship between the causative molecules has been gradually increasing. Further evidence-based systematic data of target molecules and their interactions would probably be helpful for a better understanding of the molecular mechanism underlying the dysfunction of the epidermal barrier.

Levofloxacin-induced Desquamation: A Possible and Rare Case Report

Introduction:

Levofloxacin is a fluoroquinolone active against both gram-negative and gram-positive bacteria with a well-defined margin of safety and efficacy. It has various labeled adverse effects like other fluoroquinolones but its adverse effect like desquamation is rarely reported.

Methods:

We present a case report of levofloxacin-induced desquamation in an Indian patient.

Case Report:

A-38-year old female patient presented to the outpatient department, with chief complaints of peeling off her epidermal skin. Initially, Desquamation started on her greater finger, which slowly spread to her hand, feet, lower limbs as well as upper limb and neck region. She was prescribed Levofloxacin for respiratory tract infection.

Results and Discussion:

Considering temporal relationship, upon causality assessment, (Adverse Drug Reaction) ADR was found to be likely, moderate and probable. The drug was withdrawn along with the initiation of supportive therapy and reaction subsided.

Discussion:

Although adverse drug reactions like desquamation are not fatal, this induces anxiety in the patients and reduces patient’s quality of life. This case report will help keep physicians vigilant about the current adverse drug reaction, helping in the early detection and management of ADR.

Membrane-associated mucins of the ocular surface: New genes, new protein functions and new biological roles in human and mouse

The mucosal glycocalyx of the ocular surface constitutes the point of interaction between the tear film and the apical epithelial cells. Membrane-associated mucins (MAMs) are the defining molecules of the glycocalyx in all mucosal epithelia. Long recognized for their biophysical properties of hydration, lubrication, anti-adhesion and repulsion, MAMs maintain the wet ocular surface, lubricate the blink, stabilize the tear film and create a physical barrier to the outside world. However, it is increasingly appreciated that MAMs also function as cell surface receptors that transduce information from the outside to the inside of the cell. A number of excellent review articles have provided perspective on the field as it has progressed since 1987, when molecular cloning of the first MAM was reported. The current article provides an update for the ocular surface, placing it into the broad context of findings made in other organ systems, and including new genes, new protein functions and new biological roles. We discuss the epithelial tissue-equivalent with mucosal differentiation, the key model system making these advances possible. In addition, we make the first systematic comparison of MAMs in human and mouse, establishing the basis for using knockout mice for investigations with the complexity of an in vivo system. Lastly, we discuss findings from human genetics/genomics, which are providing clues to new MAM roles previously unimagined. Taken together, this information allows us to generate hypotheses for the next stage of investigation to expand our knowledge of MAM function in intracellular signaling and roles unique to the ocular surface.

The Differentiation-Associated Keratinocyte Protein Cornifelin Contributes to Cell-Cell Adhesion of Epidermal and Mucosal Keratinocytes

Cornifelin (CNFN) has been identified as a protein component of epidermal corneocytes. Here, we investigated the tissue distribution of CNFN and potential consequences of CNFN deficiency on epithelial function in in vitro models of human skin and oral mucosa. Our detailed bioinformatics and immunostaining analysis revealed that CNFN is not only expressed in human epidermis but also in noncornifying oral mucosa. In normal epidermis, CNFN was confined to the upper granular layer and the stratum corneum. By contrast, in both partly cornifying and noncornifying oral mucosa, CNFN was expressed in a cell membrane-associated pattern over several suprabasal layers. Small interfering RNA-mediated knockdown of CNFN in epidermal keratinocytes (KCs) was associated with only subtle alterations of the overall epidermal architecture in skin models in vitro but led to altered morphology of corneodesmosomes, as detected by electron microscopy. Using dispase treatment followed by mechanical stress, epithelial sheets of CNFN-deficient epidermal KCs were easily disrupted, whereas their CNFN-competent counterparts remained intact. In contrast to the epidermal KCs, CNFN knockdown in oral KCs had a more severe effect and caused pronounced acantholysis in organotypic models of oral mucosa. Together, these findings indicate that CNFN is a structural component of the cell adhesion system of differentiated KCs in both epidermis and oral mucosa.