Porokeratosis: An enigma beginning to unravel

Porokeratoses: an update on pathogenesis and treatment

Porokeratoses (PK) are a group of uncommon dermatoses characterized by abnormal epidermal differentiation due to a disorder of the mevalonate metabolic pathway. Several clinical subtypes exist that can be associated with the same patient or affect different patients within a family and could, therefore, be different expressions of one disease. All PK subtypes share a common histopathologic finding, the cornoid lamella, a vertical stack of parakeratotic corneocytes embedded in an orthokeratotic horny layer. PK often affects immunosuppressed patients, in whom the course may parallel the level of immunosuppression. The pathogenesis of PK, which had long remained mysterious, has been recently unraveled after discovering pathogenic variants of genes involved in the mevalonate metabolic pathway. The disease is due to germline pathogenic variants of genes of this pathway but requires a second-hit event to manifest; therefore, PK is considered a dominantly inherited but recessively expressed condition. The prognosis of PK is usually favorable, even though the lesions progress to keratinocyte carcinomas in 7%-16% of patients. The treatment of PK was based on physical (ablative) procedures and various (topical or systemic) treatments, whose efficacy is nevertheless inconsistent and often temporary. The discovery of the metabolic pathway involved in the pathogenesis of PK paved the way for the elaboration of new topical treatments (combination of statins and cholesterol), which are more regularly efficacious compared with older treatments, even though the management of some patients with PK may still be challenging.

Extensive Spiculated Follicular Porokeratosis With Alopecia: A Case Report

Follicular porokeratosis (FPK) is a rare subtype of porokeratosis. Follicular porokeratosis mainly occurs in men and may be localized or diffuse. Involvement of the scalp is rarely reported, and we found only one case of alopecia due to scalp FPK. Diabetes mellitus has not been reported in association with FPK We report a 35-year-old diabetic woman that presented with brown follicular keratotic papules and spicules involving the scalp, face, trunk, and extremities, accompanied by scalp alopecia. The differential diagnoses were lichen planopilaris, papular eczema, and phrynoderma. Histopathologic examination of skin punch biopsies revealed the follicle-centered cornoid lamella as the feature of FPK. The patient was treated with oral isotretinoin, and the lesions improved partially within 6 weeks of follow-up. Follicular porokeratosis might be considered among the differential diagnoses of keratotic papules (with or without spicules) and in the cases of alopecia with keratotic papules. Diabetes mellitus may be associated with FPK.

Line-field confocal optical coherence tomography for the differential diagnosis of porokeratosis from clinical mimickers: a preliminary study

BACKGROUND

Porokeratosis variants are relatively rare and can be clinically misdiagnosed with several common papulokeratotic mimickers. Line-field confocal optical coherence tomography (LC-OCT) is a new technology able to explore the skin in vivo up to a depth of 500 µm.

OBJECTIVES

To investigate the role of LC-OCT in the diagnosis of many porokeratosis variants in a preliminary study.

METHOD

In total, 130 LC-OCT images were obtained from 98 patients, 45 affected by a porokeratosis variant (69 images) and 53 with a mimicker condition (61 images).

RESULTS

We found almost perfect interobserver agreement for LC-OCT image interpretation and perfect correspondence with the findings from histological slides. In addition, a series of morphological in vivo and three-dimensional features related to the cornoid lamella were detected by LC-OCT that were not visible from the histology.

CONCLUSIONS

This device can be proposed to assist with rapid bedside noninvasive differentiation of porokeratosis variants from their mimickers, possibly sparing incisional biopsy in patients where the diagnosis is uncertain.

Porokeratoses-A Rare Group of Dermatoses

Porokeratoses represent a rare group of skin diseases characterized by abnormal keratinization. The condition may have a genetic background and can be triggered by environmental factors, including UV exposure and infections. Several clinical variants of porokeratosis can be distinguished, including Mibelli's porokeratosis, disseminated superficial actinic porokeratosis, superficial disseminated porokeratosis, and porokeratosis palmaris plantaris et disseminata. Diagnosis is established based on clinical and histopathological examination, dermatoscopy, and reflectance confocal microscopy. Various treatment options are available, including topical combination therapy with cholesterol and statins, topical retinoids, cryotherapy, laser therapy, and surgical excision of lesions, but none are fully effective. The success of these treatments can vary significantly based on the specific type of porokeratosis and individual patient characteristics, with many outcomes falling short of expectations. Since the disease is considered a precancerous condition, patients with porokeratosis should remain under regular dermatological control.

Disseminated Superficial Non-actinic Porokeratosis: A Consequence of Post-traumatic Immunosuppression

Disseminated superficial porokeratosis (DSP) is a very uncommon dermatologic condition of unknown etiology, characterized by the clonal proliferation of atypical keratinocytes associated with aberrant keratinocyte differentiation. These lead to the development of the specific cornoid lamella that separates atypical from normal keratinocytes. DSP is most frequently encountered in immunosuppressed patients. It has been described in patients receiving immunosuppressive treatments, organ transplantation and in patients diagnosed with human immunodeficiency virus, hepatitis B and hepatitis C virus infection. We present the case of a 78-year-old patient who developed disseminated non-actinic after multiple trauma and major orthopedic surgery. To our knowledge, this is the first case of DSP occurring as a consequence of post-traumatic immunosuppression reported in the medical literature. We discuss the pathogenic mechanisms, as well as the optimal diagnostic and therapeutic approach in such cases.

Malignant Transformation in Porokeratosis Ptychotropica: A Systematic Review

Porokeratosis ptychotropica (PP) is a rare and unusual variant of porokeratosis. There is a dearth of information on the natural history, epidemiology, and optimal treatment options. This study aimed to characterize the worldwide distribution, epidemiology, clinical features, and treatments attempted for all reported cases of porokeratosis ptychotropica. A total of 59 cases of porokeratosis ptychotropica have been reported, with most cases originating from the United States. The median age of patients affected with porokeratosis ptychotropica was 49 years. The most involved body locations are the buttocks and gluteal cleft. The risk of malignant transformation in porokeratosis ptychotropica is approximately 1.7% but there is significant bias in estimating rare occurrences in rare diseases. In conclusion, PP is an important but under-recognized variant of porokeratosis, with a likely low risk of malignant transformation. The best available treatment modality remains uncertain; however, the use of topical lovastatin/cholesterol cream appears promising. Long-term surveillance appears prudent for porokeratosis ptychotropica due to a risk of cancerization.

MVD Variants Identified in a Rare Clinical Variant of Porokeratosis: A Case Report of Disseminated Superficial Porokeratosis (DSP) in a Chinese Patient

Porokeratosis comprises a diverse range of both hereditary and acquired disorders characterized by clonal hyperproliferation of keratinocytes. These disorders manifest with a variety of clinical presentations but are histologically unified by the presence of the cornoid lamella. In this study, we report an unusual presentation of a rare clinical variant of porokeratosis, namely disseminated superficial porokeratosis, in which mutations in the Mevalonate decarboxylase (MVD) gene have been identified. This finding contributes to the growing understanding of the genetic underpinnings of this complex dermatological condition and may have implications for diagnosis and treatment.

Conventional and Novel Treatment Strategies for Porokeratoses: A Narrative Review

Porokeratoses are a heterogenous group of autoinflammatory keratinization disorders all characterized by the presence of a cornoid lamella. In addition to gene mutations affecting the mevalonate pathway, environmental factors such as UV radiation, immunosuppression, trauma, and infection are also thought to contribute to porokeratoses. To date, there are no management guidelines or levels of evidence for commonly used pharmacologic and non-pharmacologic treatment options for porokeratoses. Conventional treatment strategies encompass topical and systemic drugs (e.g., salicylic acid, topical glucocorticoids, and retinoids), phototherapy, laser, and surgical interventions. Better insights into the pathogenesis of porokeratoses have paved the way for the development of novel therapeutic approaches, such as topical statins or the use of monoclonal antibodies. This narrative review aims to summarize both conventional and novel treatment options, including their level of evidence, advantages, and disadvantages.

Konventionelle und neue Behandlungsstrategien bei Porokeratosen: Eine narrative Übersicht

Porokeratosen sind eine heterogene Gruppe autoinflammatorischer Keratinisierungsstörungen, die durch kornoide Lamellen gekennzeichnet sind. Neben Genmutationen, die sich auf den Mevalonat‐Stoffwechselweg auswirken, werden auch Umweltfaktoren wie UV‐Strahlung, Immunsuppression, Traumata und Infektionen für die Entstehung von Porokeratosen verantwortlich gemacht. Bislang gibt es keine Behandlungsrichtlinien oder Evidenzgrade für die gängigen pharmakologischen und nicht‐pharmakologischen Behandlungsoptionen bei Porokeratosen. Zu den konventionellen Behandlungen zählen topische und systemische Medikamente wie Salicylsäure, topische Glucocorticoide und Retinoide, Phototherapie, Laser und chirurgische Verfahren. Bessere Erkenntnisse über die Pathogenese von Porokeratosen haben die Entwicklung neuartiger therapeutischer Ansätze ermöglicht, etwa topische Statine oder monoklonale Antikörper. In dieser narrativen Übersichtsarbeit werden sowohl die herkömmlichen als auch neuen Behandlungsmöglichkeiten einschließlich ihres Evidenzgrads sowie ihrer Vor‐ und Nachteile zusammengefasst.

A Clinico-Epidemiological Study on Porokeratosis

Porokeratosis (PK) is a chronic progressive disorder of keratinization characterized clinically by hyperkeratotic papules or plaques surrounded by a threadlike, elevated border that expands centrifugally. Pathogenesis involves heterozygous mutations in mevalonate kinase enzyme. The most common variants are disseminated superficial actinic porokeratosis (DSAP) and PK of Mibelli. All forms show a thin column of parakeratosis, the cornoid lamella, representing the active border. Dermoscopy reveals central brownish discoloration surrounded by a single hypopigmented band and a peripheral 'white track'. Long-standing cases of PK may undergo malignant transformation. UV-protection and topical agents, such as 5-fluorouracil, imiquimod, calcipotriol, tretinoin and oral retinoids are helpful. To study the clinical and epidemiological pattern of PK and the clinico-dermoscopic and histopathological correlation of PK. A prospective cross-sectional study was conducted on the patients attending the dermatology outpatient department (OPD) over 9 months with suspected features of PK. These patients were evaluated clinically and subjected to dermoscopy and histopathology. Statistical Package for the Social Sciences (SPSS) Of 11 patients, there were four (36.36%) males and seven (63.66%) females. The youngest was 18-year-old boy, and the eldest was 63-year-old man. The clinically most common type was PK of Mibelli with five (45.45%) cases. The most common dermoscopic feature observed was double-marginated, white peripheral border. The most common histopathological feature noted was cornoid lamella. PK is a rare skin disorder with a wide spectrum of clinical variants. Dermoscopy and histopathology aid in diagnosis, whereas dermoscopy plays a pivotal role in early and non-invasive diagnosis. Regular follow-up is mandatory to watch for the development of malignancies in a few variants.

A Case of Squamous Cell Carcinoma Arising in Disseminated Superficial Porokeratosis

Porokeratosis (PK), characterized by keratotic lesions with an atrophic center and a prominent peripheral ridge, with a typical histological hallmark, namely, the cornoid lamella, has two forms: disseminated and localized. While PK often converts into squamous cell carcinoma (SCC), conversion from disseminated superficial porokeratosis (DSP) alone is rarely reported except for one case in which DSP and LP coexisted and converted to SCC. Here, we report the case of a patient with SCC converted from DSP alone, presenting with coin-sized macules on the bottom right of his waist that developed into an ulcer at the center. The patient underwent radiation therapy, which effectively treated the SCC but did not resolve the PK. This article highlights regular follow-up and undergo comprehensive diagnosis, both of which are beneficial to enable early detection and management of DSP that has converted to into SCC; in addition, standardized medical treatment may help improve the treatment therapeutic effect of in similar diseases.

Gene-specific somatic epigenetic mosaicism of FDFT1 underlies a non-hereditary localized form of porokeratosis

Porokeratosis is a clonal keratinization disorder characterized by solitary, linearly arranged, or generally distributed multiple skin lesions. Previous studies showed that genetic alterations in MVK, PMVK, MVD, or FDPS-genes in the mevalonate pathway-cause hereditary porokeratosis, with skin lesions harboring germline and lesion-specific somatic variants on opposite alleles. Here, we identified non-hereditary porokeratosis associated with epigenetic silencing of FDFT1, another gene in the mevalonate pathway. Skin lesions of the generalized form had germline and lesion-specific somatic variants on opposite alleles in FDFT1, representing FDFT1-associated hereditary porokeratosis identified in this study. Conversely, lesions of the solitary or linearly arranged localized form had somatic bi-allelic promoter hypermethylation or mono-allelic promoter hypermethylation with somatic genetic alterations on opposite alleles in FDFT1, indicating non-hereditary porokeratosis. FDFT1 localization was uniformly diminished within the lesions, and lesion-derived keratinocytes showed cholesterol dependence for cell growth and altered expression of genes related to cell-cycle and epidermal development, confirming that lesions form by clonal expansion of FDFT1-deficient keratinocytes. In some individuals with the localized form, gene-specific promoter hypermethylation of FDFT1 was detected in morphologically normal epidermis adjacent to methylation-related lesions but not distal to these lesions, suggesting that asymptomatic somatic epigenetic mosaicism of FDFT1 predisposes certain skin areas to the disease. Finally, consistent with its genetic etiology, topical statin treatment ameliorated lesions in FDFT1-deficient porokeratosis. In conclusion, we identified bi-allelic genetic and/or epigenetic alterations of FDFT1 as a cause of porokeratosis and shed light on the pathogenesis of skin mosaicism involving clonal expansion of epigenetically altered cells.

Autoinflammatory Keratinization Diseases-The Concept, Pathophysiology, and Clinical Implications

Recent advances in medical genetics elucidated the background of diseases characterized by superficial dermal and epidermal inflammation with resultant aberrant keratosis. This led to introducing the term autoinflammatory keratinization diseases encompassing entities in which monogenic mutations cause spontaneous activation of the innate immunity and subsequent disruption of the keratinization process. Originally, autoinflammatory keratinization diseases were attributed to pathogenic variants of CARD14 (generalized pustular psoriasis with concomitant psoriasis vulgaris, palmoplantar pustulosis, type V pityriasis rubra pilaris), IL36RN (generalized pustular psoriasis without concomitant psoriasis vulgaris, impetigo herpetiformis, acrodermatitis continua of Hallopeau), NLRP1 (familial forms of keratosis lichenoides chronica), and genes of the mevalonate pathway, i.e., MVK, PMVK, MVD, and FDPS (porokeratosis). Since then, endotypes underlying novel entities matching the concept of autoinflammatory keratinization diseases have been discovered (mutations of JAK1, POMP, and EGFR). This review describes the concept and pathophysiology of autoinflammatory keratinization diseases and outlines the characteristic clinical features of the associated entities. Furthermore, a novel term for NLRP1-associated autoinflammatory disease with epithelial dyskeratosis (NADED) describing the spectrum of autoinflammatory keratinization diseases secondary to NLRP1 mutations is proposed.

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.

Successful Treatment of Eruptive Pruritic Papular Porokeratosis in the Elderly with Tofacitinib: A Case Report

Eruptive pruritic papular porokeratosis (EPPP) is a rare subtype of porokeratosis that presents as an acute exacerbation of an annular papule with a distinct peripheral hyperkeratotic ridge border and severe pruritus. EPPP is mainly reported in elderly East Asian men. Its etiology and pathogenesis are unknown. We hereby present a case report of EPPP in a 68-year-old Chinese male with persistent circumscribed papules on the extremities, accompanied by severe pruritus for one year. After the patient was given conventional medication, a new rash appeared on the patient's extremities and he felt intense itching in the area of the rash. The patient was switched to oral tofacitinib treatment. The patient felt that the pruritus had largely disappeared after one month of oral dosing, leaving only brown pigmentation on the erythema of the extremities. The patient has been off the drug for 2 months. There was no pruritus or new rash during the follow-up period.

Disseminated Superficial Actinic Porokeratosis (DSAP): A Case Report Highlighting the Clinical, Dermatoscopic, and Pathology Features of the Condition

Porokeratosis describes a heterogenic group of keratinization disorders in which lesions are papules and plaques that demonstrate central atrophy surrounded by a hyperkeratotic margin. Clinical variants include not only porokeratosis of Mibelli, but also disseminated superficial, disseminated actinic superficial, linear, punctate, and palmaris et plantaris disseminata. Porokeratosis has a risk of malignant transformation. A woman with disseminated superficial actinic porokeratosis (DSAP) whose lesions presented as pruritic plaques and papules is described. The diagnosis was suspected clinically, supported by dermoscopy findings, and confirmed histologically. The condition-associated pruritus was managed symptomatically; her skin lesions will be monitored clinically. Clinical manifestations, dermatoscopic features, pathology findings, and treatment options for DSAP are summarized.