Gene expression profiling of porokeratosis demonstrates similarities with psoriasis

Porokeratoses-A Comprehensive Review on the Genetics and Metabolomics, Imaging Methods and Management of Common Clinical Variants

Porokeratosis is a heterogeneous group of keratinising disorders characterised by the presence of particular microscopic structural changes, namely the presence of the cornoid lamella. This structure develops as a consequence of a defective isoprenoid pathway, critical for cholesterol synthesis. Commonly recognised variants include disseminated superficial actinic porokeratosis, disseminated superficial porokeratosis, porokeratosis of Mibelli, palmoplantar porokeratosis (including porokeratosis palmaris et plantaris disseminata and punctate porokeratosis), linear porokeratosis, verrucous porokeratosis (also known as genitogluteal porokeratosis), follicular porokeratosis and porokeratoma. Apart from the clinical presentation and epidemiology of each variant listed, this review aims at providing up-to-date information on the precise genetic background, introduces imaging methods facilitating the diagnosis (conventional and ultraviolet-induced fluorescence dermatoscopy, reflectance confocal microscopy and pathology), discusses their oncogenic potential and reviews the literature data on the efficacy of the treatment used, including the drugs directly targeting the isoprenoid-mevalonate pathway.

Red Flat Papules on the Abdomen and Lower Limbs of an Old Woman

Psoriasis and porokeratosis are two common skin diseases. Nevertheless, the occurrence of comorbidity is rare. To the best of our knowledge, these kinds of clinical histopathologic features of comorbidity were rarely reported previously. Here, we describe a case of a 75-year-old patient who presented with diffused porokeratosis in association with psoriasis.

Decreased Imiquimod-Induced Psoriasis-Like Skin Inflammation in a Novel MvdF250S/+ Knock-In Mouse Model

The mevalonate-diphosphate decarboxylase (MVD) gene, a member of the mevalonate pathway, plays a critical role in regulating the biosynthesis of cholesterol, steroid hormones, and non-steroid isoprenoids. Previous studies have suggested that the MVD c.746 T > C mutation is a major pathogenic gene of porokeratosis (PK), an autoinflammatory keratinization disease (AIKD) with unclear pathogenesis, few effective treatments, and no suitable animal model. To investigate the function of Mvd^F250S/+ mutation, we developed a novel Mvd^F250S/+ mouse model carrying an equivalent point mutation to the most common genetic variation among Chinese PK patients (MVD^F249S/+) using CRISPR/Cas9 technology, which exhibited reduced cutaneous expression of Mvd protein. In the absence of external stimulation, Mvd^F250S/+ mice did not display specific phenotypes. However, upon induction with imiquimod (IMQ), Mvd^F250S/+ mice exhibited decreased susceptibility to skin acute inflammation compared to wild-type (WT) mice, as evidenced by reduced cutaneous proliferation and lower protein levels of IL-17a and IL-1β. Additionally, after IMQ induction, the Mvd^F250S/+mice exhibited downregulated collagen generation and upregulated expression of Fabp3 compared to WT mice, whereas no significant changes in the key genes related to cholesterol regulation were found. Furthermore, the Mvd^F250S/+ mutation activated autophagy. Our findings provided insights into the biological function of MVD in the skin.

Crosstalk between cholesterol metabolism and psoriatic inflammation

Psoriasis is a chronic autoinflammatory skin disease associated with multiple comorbidities, with a prevalence ranging from 2 to 3% in the general population. Decades of preclinical and clinical studies have revealed that alterations in cholesterol and lipid metabolism are strongly associated with psoriasis. Cytokines (tumor necrosis factor-α (TNF-α), interleukin (IL)-17), which are important in the pathogenesis of psoriasis, have been shown to affect cholesterol and lipid metabolism. Cholesterol metabolites and metabolic enzymes, on the other hand, influence not only the biofunction of keratinocytes (a primary type of cell in the epidermis) in psoriasis, but also the immune response and inflammation. However, the relationship between cholesterol metabolism and psoriasis has not been thoroughly reviewed. This review mainly focuses on cholesterol metabolism disturbances in psoriasis and their crosstalk with psoriatic inflammation.

Porokeratotic eccrine ostial and dermal duct nevus associated with an 11 megabase 3p deletion

Porokeratotic eccrine ostial and dermal duct nevus (PEODDN) is a rare eccrine hamartoma; the etiology is incompletely understood. A patient presented with congenital, widespread PEODDN. Clinical assessment, histopathologic, cytogenetic, and molecular genetic investigations on affected cells were pursued. Histopathology confirmed PEODDN, and chromosomal microarray on affected tissues identified a mosaic 3p26.3p25.3 deletion in affected tissues. This 11Mb deletion encompasses 47 OMIM genes. We propose that this and other chromosomal deletions may be implicated in some cases of PEODDN, suggesting locus heterogeneity and underscoring the importance of incorporating cytogenetic and molecular investigations into the multidisciplinary care of individuals with suspected mosaic genetic skin disorders.

Drugs associated with development of porokeratosis: A systematic review

Porokeratosis is a rare disorder characterized by atrophic macules or patches, with a well-defined ridge-like hyperkeratotic border called cornoid lamella. Although the exact pathogenesis is unknown, drug associated cases have recently been reported in the literature. As such, we systematically reviewed and identified drugs associated with drug-induced porokeratosis, their resultant effects, and whether there was a casual relationship between the use of a drug and the development of porokeratosis. We searched for articles which reported drug-induced porokeratosis in MEDLINE and Embase in June 2020. After full-text review, 25 studies were included for analysis. We identified 26 patients with drug-induced porokeratosis. The most common therapies associated with development of porokeratosis is biologic use, phototherapy, and radiotherapy. The most common clinical variants were the disseminated superficial or actinic types (60%), which occurred in psoriasis patients undergoing phototherapy, and eruptive disseminated type (24%) which occurred in the context of biologic therapies. The Naranjo score ranged from possible to probable for the identified treatments. Clinicians should consider drug reactions as possible triggering events for porokeratosis, especially for patients taking biologics, phototherapy, and radiotherapy. Large-scale studies are required to confirm our findings and further explore the pathogenesis for drug-induced porokeratosis.

Linear porokeratosis associated with Bardet-Biedl syndrome: A case report

This case report presents a 17-year-old boy with Bardet-Biedl syndrome (BBS) and a long-standing hyperpigmented eruption on the left trunk and upper extremity, clinically and histologically consistent with linear porokeratosis (LP). BBS patients frequently require solid organ transplant, and subsequent immunosuppression places them at especially high risk for malignant transformation of premalignant skin lesions such as LP. Although BBS affects multiple organ systems, there are only a handful of case reports detailing associated cutaneous involvement, and, to our knowledge, this is the first reported case of linear porokeratosis occurring in patient with BBS.

Connexin Communication Compartments and Wound Repair in Epithelial Tissue

Epithelial tissues line the lumen of tracts and ducts connecting to the external environment. They are critical in forming an interface between the internal and external environment and, following assault from environmental factors and pathogens, they must rapidly repair to maintain cellular homeostasis. These tissue networks, that range from a single cell layer, such as in airway epithelium, to highly stratified and differentiated epithelial surfaces, such as the epidermis, are held together by a junctional nexus of proteins including adherens, tight and gap junctions, often forming unique and localised communication compartments activated for localised tissue repair. This review focuses on the dynamic changes that occur in connexins, the constituent proteins of the intercellular gap junction channel, during wound-healing processes and in localised inflammation, with an emphasis on the lung and skin. Current developments in targeting connexins as corrective therapies to improve wound closure and resolve localised inflammation are also discussed. Finally, we consider the emergence of the zebrafish as a concerted whole-animal model to study, visualise and track the events of wound repair and regeneration in real-time living model systems.

Keratins K2 and K10 are essential for the epidermal integrity of plantar skin

BACKGROUND

K1 and K2 are the main type II keratins in the suprabasal epidermis where each of them heterodimerizes with the type I keratin K10 to form intermediate filaments. In regions of the ears, tail, and soles of the mouse, only K2 is co-expressed with K10, suggesting that these keratins suffice to form a mechanically resilient cytoskeleton.

OBJECTIVE

To determine the effects of the suppression of both main keratins, K2 and K10, in the suprabasal plantar epidermis of the mouse.

METHODS

Krt2(-/-) Krt10(-/-) mice were generated by crossing Krt2(-/-) and Krt10(-/-) mice. Epidermal morphology of soles of hind-paws was examined macroscopically and histologically. Immunofluorescence analysis and quantitative PCR analysis were performed to analyze the expression of keratins in sole skin of wildtype and Krt2(-/-) Krt10(-/-) mice. Highly abundant proteins of the sole stratum corneum were determined by electrophoretic and chromatographic separation and subsequent mass spectrometry.

RESULTS

K2 and K10 are the most prominent suprabasal keratins in normal mouse soles with the exception of the footpads where K1, K9 and K10 predominate. Mice lacking both K2 and K10 were viable and developed epidermal acanthosis and hyperkeratosis in inter-footpad epidermis of the soles. The expression of keratins K1, K9 and K16 was massively increased at the RNA and protein levels in the soles of Krt2(-/-) Krt10(-/-) mice.

CONCLUSIONS

This study demonstrates that the loss of the main cytoskeletal components of plantar epidermis, i.e. K2 and K10, can be only partly compensated by the upregulation of other keratins. The thickening of the epidermis in the soles of Krt2(-/-) Krt10(-/-) mice may serve as a model for pathomechanistic aspects of palmoplantar keratoderma.

Connexin hemichannels influence genetically determined inflammatory and hyperproliferative skin diseases

Connexin mutations underlie numerous human genetic diseases. Several connexin genes have been linked to skin diseases, and mechanistic studies have indicated that a gain of abnormal channel function may be responsible for pathology. The topical accessibility of the epidermal connexins, the existence of several mouse models of human skin disease, and the ongoing identification of pharmacological inhibitors targeting connexins provide an opportunity to test new therapeutic approaches.

Cornoid lamellation revisited: apropos of porokeratosis with emphasis on unusual clinicopathological variants

Porokeratosis is a family of several disorders characterized histologically by the presence of cornoid lamellae. The presence of cornoid lamellae represents an abnormal form of keratinization, which unifies all types of porokeratosis. A significant variation in lesional morphology can result from peculiarities involving the cornoid lamellae and changes related to epidermal hyperplasia and dermal inflammation. This diversity has led to the recognition of several unusual clinicopathological variants of porokeratosis in recent years. Cornoid lamellation, however, is not pathognomonic of porokeratosis and can be seen in some inflammatory and inherited cutaneous disorders and also as an incidental finding. Some of these conditions can be confused with an atypical presentation of porokeratosis and vice versa. An awareness of the broad morphological spectrum of porokeratosis is crucial to avoid missing the diagnosis when appearances are far from typical. This issue is critical in patient management given the potential premalignant nature of porokeratosis.

Connexins: sensors of epidermal integrity that are therapeutic targets

Gap junction proteins (connexins) are differentially expressed throughout the multiple layers of the epidermis. A variety of skin conditions arise with aberrant connexin expression or function and suggest that maintaining the epidermal gap junction network has many important roles in preserving epidermal integrity and homeostasis. Mutations in a number of connexins lead to epidermal dysplasias giving rise to a range of dermatological disorders of differing severity. 'Gain of function' mutations reveal connexin-mediated roles in calcium signalling within the epidermis. Connexins are involved in epidermal innate immunity, inflammation control and in wound repair. The therapeutic potential of targeting connexins to improve wound healing responses is now clear. This review discusses the role of connexins in epidermal integrity, and examines the emerging evidence that connexins act as epidermal sensors to a variety of mechanical, temperature, pathogen-induced and chemical stimuli. Connexins thus act as an integral component of the skin's protective barrier.

Connexin dynamics in the privileged wound healing of the buccal mucosa

Wound closure is fundamental to maintaining tissue homeostasis; a plethora of processes and signals must be coordinated, and gap junctions play a critical role. Some tissues exhibit privileged healing, such as buccal mucosa, repairing more rapidly, but gap junction connexin dynamics during wound healing in such tissues have not been investigated. To determine connexin changes during this rapid healing process, incisional wounds were made in the cheeks of mice and microscopically observed. We discovered that buccal mucosa wound edge keratinocytes do not form a thin tongue of migratory cells like epidermis; instead, a wedge of cells rapidly moves into the wound. The dorsal surfaces of opposing sides of the wounds then touch and join in a "V," which subsequently fills up with cells to form a "delta" that remodels into a flat sheet. Immunostaining showed that connexin26, connexin30, and connexin43 are expressed at significantly higher levels in the buccal mucosa than the epidermis and that, unlike the skin, all three are rapidly down-regulated at the wound edge within 6 hours of wounding. This rapid down-regulation of all three connexins may in part underlie the rapid healing of the buccal mucosa.

Identification of an interstitial 18p11.32-p11.31 duplication including the EMILIN2 gene in a family with porokeratosis of Mibelli

Porokeratosis is a rare disease of epidermal keratinization characterized by the histopathological feature of the cornoid lamella, a column of tightly fitted parakeratocytic cells, whose etiology is still unclear. Porokeratosis of Mibelli is a subtype of porokeratosis presenting a single plaque or a small number of plaques of variable size located unilaterally on limbs. It frequently appears in childhood and occurs with a higher incidence in males. Cytogenetic analyses were performed in all members of the family on lesioned and uninvolved skin. An array-CGH analysis was also performed utilizing the Human Genome CGH Microarray Kit G3 400 with 5.3 KB overall median probe spacing. Gene expression was performed on skin fibroblasts. In this study, we describe a Caucasian healthy 4-year-old child and his father showing features of porokeratosis of Mibelli. Array-CGH analysis revealed an interstitial 429.5 Kb duplication of chromosome 18p11.32-p11.3 containing four genes, namely: SMCHD1, EMILIN2, LPIN2, and MYOM1 both in patient and his father. EMILIN2 resulted overexpressed on skin fibroblasts. Also other members of this family, without evident signs of porokeratosis, carried the same duplication. Among these genes, we focused our attention on elastin microfibril interfacer 2 (EMILIN2) gene. Apoptosis plays a fundamental role in maintaining epidermal homeostasis, balancing keratinocytes proliferation, and forming the stratum corneum. EMILIN2 is known to trigger the apoptosis of different cell lines negatively affecting cell survival. It is expressed in the skin. We could speculate that the duplication and overexpression of EMILIN2 cause an abnormal apoptosis of epidermal keratinocytes and alter the process of keratinization, even if other epigenetic and genetic factors could also be involved. Our results could contribute to a better understanding of the pathogenesis of porokeratosis of Mibelli.

Giant verrucous porokeratosis of Mibelli mimicking psoriasis in a patient with psoriasis

Porokeratosis of Mibelli is a disorder of epidermal keratinization characterized by annular plaques with an atrophic center surrounded by a keratotic wall. We report a case of a giant verrucous porokeratosis of Mibelli mimicking psoriasis that developed in a patient with psoriasis and therefore went unrecognized for a long time. Histologically the lesion combined features of porokeratosis at the periphery and of psoriasis at its center, a picture recently described as "psoriasis encircled by porokeratosis." The possible pathogenetic relationship between psoriasis and the development of porokeratosis is also discussed.

Porokeratosis of Mibelli induced by topical corticosteroid

BACKGROUND

[corrected] Prorokeratosis of Mibelli is a chronic disorder characterised by slightly atrophic plaques surrounded by keratotic border.

METHODS AND RESULTS

A 45-year-old with clobetazole propionate ointment for psoriasis over 15 years developed characteristic lesions of porokeratosis Mibelli on the elbows. Histopathological examination revealed the cornoid lamellae located on the edges of the specimen and psoriasiform acanthosis and a spongiotic pustule formation in the center of the specimen; thus, it was suggested as 'psoriasis encircled by porokeratosis'.

CONCLUSIONS

Development of porokeratosis may be explained by the local immunosuppressive effect of the prolonged application of the topical steroid.

Characterization of a new syndrome that associates craniosynostosis, delayed fontanel closure, parietal foramina, imperforate anus, and skin eruption: CDAGS

We describe the clinical characterization, molecular analyses, and genetic mapping of a distinct genetic condition characterized by craniosynostosis, delayed closure of the fontanel, cranial defects, clavicular hypoplasia, anal and genitourinary malformations, and skin eruption. We have identified seven patients with this phenotype in four families from different geographic regions and ethnic backgrounds. This is an autosomal recessive condition that brings together apparently opposing pathophysiologic and developmental processes, including accelerated suture closure and delayed ossification. Selected candidate genes--including RUNX2, CBFB, MSX2, ALX4, TWIST1, and RECQL4--were screened for mutations, by direct sequencing of their coding regions, and for microdeletions, by fluorescent in situ hybridization. No mutations or microdeletions were detected in any of the genes analyzed. A genomewide screen yielded the maximum estimated LOD score of +2.38 for markers D22S283 and D22S274 on chromosome 22q12-q13. We hypothesize that the gene defect in this condition causes novel context-dependent dysregulation of multiple signaling pathways, including RUNX2, during osteoblast differentiation and craniofacial morphogenesis.