Porokeratosis: present concepts

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.

Spiny Keratoderma: Clinical and Histopathological Findings in a Series of 3 Cases

ABSTRACT

Spiny keratoderma is a rare entity presenting with minute keratotic spines on the palms and soles. Spiny keratoderma can be inherited or acquired, and the acquired form may be associated with underlying malignancy or systemic disease. Clinically, the differential diagnosis includes other digitate keratoses on acral sites, most notably arsenical keratosis, filiform verruca, and punctate porokeratosis. Biopsy findings typically include a column of parakeratosis overlying a diminished granular cell layer. In this article, we present 3 cases of acquired spiny keratoderma in patients with various systemic diseases, but no underlying malignancy.

Annular Pigmented Macules on the Upper Trunk: A Quiz

Abstract is missing (Quiz)

Challenges in the Diagnosis and Management of Giant Porokeratosis: A Case Report

Porokeratosis encompasses a diverse group of dermatoses, both acquired and genetic, marked by a keratinization disorder. Porokeratosis of Mibelli (PKM) presents as solitary plaques or multiple papules/macules with central atrophy and raised hyperkeratotic borders. Here, we present a case of giant porokeratosis (GPK), a rare form often considered a morphological variant of PKM, with unique clinical and histopathological aspects. Our case involves a 29-year-old patient with a 15 × 10 cm irregular plaque on the dorsal aspect of the right hand. The patient was previously prescribed various topical treatments (retinoids, calcineurin inhibitors, and combinations of corticosteroids with vitamin D3 analogs) and systemic retinoids without improvement before presenting to our department. Due to the high risk of neoplastic transformation and the unavailability of imiquimod, the patient was recommended topical 5-fluorouracil treatment. The trajectory of the lesion under treatment revealed a favorable evolution, and the patient was subjected to regular monitoring every three months to assess the ongoing progress. Recognizing GPK as a high-risk variant is crucial for dermatologists, and it requires a personalized approach. Regular monitoring is advised to detect potential malignant transformations promptly. Future research holds promise for diagnostic advancements, refined treatment modalities, and a deeper understanding of the molecular mechanisms underlying malignancy in porokeratosis.

Clinical-pathologic correlation: The impact of grossing at the bedside

The unenlightened clinician may submit a skin specimen to the lab and expect an "answer." The experienced clinician knows that in performing skin biopsies, it is critical to select the most appropriate: 1) anatomic location for the biopsy1,2; 2) type of biopsy1,2; 3) depth and breadth of the biopsy; and 4) medium for hematoxylin and eosin staining (formalin) or direct immunofluorescence (Michel's Transport Medium or normal saline).2 Demographic information, anatomic location, clinical context, and differential diagnosis are all critical components of a properly completed requisition form.3-5 Proper biopsy design and appropriate grossing of the tissue at the bedside should be added to this list. In this article, we review the basics of gross pathologic examination and then provide four examples to demonstrate that optimal clinical-pathologic correlation requires the clinician consider the needs of the pathologist when tissue is presented to the lab.

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.

Bilateral Linear Porokeratosis Treated With Topical Lovastatin 2% Monotherapy

Linear porokeratosis is a rare skin disorder that presents along dermatomal or Blashko lines. While the mechanism of linear porokeratosis formation is unknown, both disrupted cholesterol synthesis and mevalonate accumulation have been proposed as possible theories. There is a small chance of transforming into cutaneous malignancies, most commonly squamous cell carcinomas. The patient is a 61-year-old male with an unusual presentation of bilateral linear porokeratosis. His condition provided a unique opportunity to compare the efficacy of topical treatments in a single individual. A previous trial had successfully cleared the porokeratosis plaques with topical cholesterol 2%/lovastatin 2% on the patient's right arm. After a 12-week trial of topical lovastatin 2% monotherapy on the left arm, our current study demonstrated a comparable reduction of porokeratosis lesions. In our PubMed search, there has been a single reported case of disseminated superficial actinic porokeratosis successfully treated with topical lovastatin 2% monotherapy, but there have not been any reported cases of linear porokeratosis treated with this therapy. While topical lovastatin monotherapy for porokeratosis subvariants requires further studies, this case demonstrates similar efficacy of treating linear porokeratosis with topical lovastatin compared to cholesterol/lovastatin dual therapy. These findings support the theory of mevalonate accumulation as a more likely cause of linear porokeratosis compared to disruption of cholesterol synthesis.

Porokeratosis is one of the most common genodermatoses and is associated with an increased risk of keratinocyte cancer and melanoma

BACKGROUND

Porokeratosis is a clinically heterogeneous group of keratinization disorders with a genetic background mainly affecting the mevalonate pathway, which is involved in the synthesis of cholesterol, an essential component for the formation of the extracellular lipid lamellae in the stratum corneum. Porokeratosis is reportedly associated with an increased risk of keratinocyte cancer, but to date, no large epidemiological studies have been conducted to further address this association.

OBJECTIVES

The first objective was to characterize a cohort of patients diagnosed with porokeratosis at the Department of Dermatology and Venereology, Sahlgrenska University Hospital (SU), Gothenburg, Sweden. The second objective was to conduct a nationwide registry-based cohort study to investigate the association, if any, between porokeratosis and the cutaneous malignancies squamous cell carcinoma (SCC), basal cell carcinoma (BCC) and melanoma.

METHODS

For the SU cohort, the hospital registry was searched for patients with a diagnosis of porokeratosis recorded between 2016 and 2020. Clinical data were extracted from the records of the identified patients. For the nationwide cohort, national registries were searched to identify patients with a diagnosis of porokeratosis between 2001 and 2020. A tenfold control cohort was formed by Statistics Sweden. The data was cross-referenced with the Swedish Cancer Register to study the associations between porokeratosis and SCC, BCC and melanoma.

RESULTS

Disseminated superficial actinic porokeratosis was the most common clinical type among the 108 patients in the SU cohort. In the nationwide search, 2277 patients with porokeratosis were identified (prevalence 1/4132). Porokeratosis was associated with an increased risk for SCC, BCC and melanoma with hazard ratios (95% CI) of 4.3 (3.4-5.4), 2.42 (1.97-2.98) and 1.83 (1.18-2.82), respectively, in the patient cohort, compared to the matched control group.

CONCLUSION

Porokeratosis is a common genodermatosis, and it is associated with an enhanced risk of skin cancer.

MicroRNA-874 targets phosphomevalonate kinase and inhibits cancer cell growth via the mevalonate pathway

The microRNA (miR) miR-874, a potential tumour suppressor, causes cell death via target gene suppression in various cancer types. Mevalonate pathway inhibition also causes cell death in breast cancer. However, the relationship between the mevalonate pathway and miR-874-induced apoptosis or its association with the tumour suppressor p53 has not been elucidated. We identified phosphomevalonate kinase (PMVK), a key mevalonate pathway enzyme, and sterol regulatory element-binding factor 2 (SREBF2), the master cholesterol biosynthesis regulator, as direct miR‑874 targets. Next-generation sequencing analysis revealed a significant miR-874-mediated downregulation of PMVK and SREBF2 gene expression and p53 pathway enrichment. Luciferase reporter assays showed that miR-874 directly regulated PMVK and SREBF2. miR-874-induced apoptosis was p53 dependent, and single-cell RNA sequencing analysis demonstrated that miR-874 transfection resulted in apoptosis and p53 pathway activation. Downregulation of PMVK expression also caused cell cycle arrest and p53 pathway activation, which was rescued by geranylgeranyl pyrophosphate (GGPP) supplementation. Analysis of The Cancer Genome Atlas (TCGA) database indicated a negative correlation between miR-874 and PMVK expression and between miR-874 and SREBF2 expression. These findings suggest that miR-874 suppresses the mevalonate pathway by targeting SREBF2 and PMVK, resulting in GGPP depletion, which activates the p53 pathway and promotes cycle arrest or apoptosis.

Annular lichenoid diseases

Annular lichenoid diseases encompass a diverse range of pathologies that present as circular, raised, or flat lesions that may vary in size and number. Examples include annular lichenoid dermatitis of youth, annular lichen planus, erythema dyschromicum perstans, erythema multiforme, fixed drug eruption, lichen sclerosus, neonatal lupus, porokeratosis, subacute cutaneous lupus erythematosus, and lichenoid syphilis. Clinical morphology and histopathology can differentiate these entities.

Twists and turns of the genetic story of mevalonate kinase-associated diseases: A review

Mevalonate kinase (MK)-associated diseases encompass a broad spectrum of rare auto-inflammatory conditions, all resulting from pathogenic variants in the mevalonate kinase gene (MVK). Their clinical manifestations are highly variable, ranging from more or less serious systemic disorders, such as hereditary recurrent fevers, to purely localized pathologies such as porokeratosis. The oldest condition identified as linked to this gene is a metabolic disease called mevalonic aciduria, and the most recent is disseminated superficial actinic porokeratosis, a disease limited to the skin. The modes of inheritance of MK-associated diseases also diverge among the different subtypes: recessive for the systemic subtypes and dominant with a post-zygotic somatic genetic alteration for MVK-associated porokeratosis. This review quickly retraces the historical steps that led to the description of the various MK-associated disease phenotypes and to a better understanding of their pathophysiology, then summarizes and compares the different genetic mechanisms involved in this group of disorders, and finally discusses the diverse causes that could underlie this phenotypic heterogeneity.

Mixed porokeratosis with a novel mevalonate kinase gene mutation: A case report

BACKGROUND

Porokeratosis is a rare, acquired, or inherited disorder of keratinization. There are numerous clinical types of porokeratosis and they can coexist in one patient and multiple members of an affected family. However, coexistence of disseminated superficial actinic porokeratosis (DSAP) and porokeratosis ptychotropica (Ppt) is rare.

CASE SUMMARY

A 45-year-old man presented with long-standing skin lesions. Physical examination identified numerous small, brown 2-mm to 4-mm patches on his face and several hyperkeratotic, verrucous plaques on his trunk and extremities. His father and one of his brothers also had similar lesions for years. Skin biopsies indicated a cornoid lamella in the epidermis. We identified c.155G>A mutation in the mevalonate kinase (MVK) gene, which converted a serine residue to asparagine (p.Ser52Asn) and was causative for porokeratosis in this family. A clinicopathologic diagnosis of DSAP and Ppt with a novel MVK gene mutation was made. The hyperkeratotic plaques on the patient’s scrotum were completely removed more than 10 times using a microwave knife.

CONCLUSION

An unusual case of DSAP coexisting with Ppt harbored a novel MVK gene mutation also present in the patient’s family.

Porokeratosis of gluteal region: A case report

Genitogluteal porokeratosis is a rare localized disorder of keratinization. Due to the rarity of the case and non-specific keratotic lesion, it is often misdiagnosed until a histological examination is performed. Treatment of this condition can be challenging, which comprises various topical and systemic drugs, lasers, cryotherapy, phototherapy, and also surgical intervention. Regular follow-up is necessary in the view of this disorder being a premalignant condition.

[CME Dermatology 24: Porokeratosis]

CME Dermatology 24: Porokeratosis Abstract. Porokeratoses are a heterogeneous group of cornification disorders with the characteristic histological feature of the cornoid lamellae in the area of the marginal ridge. It is a rare but characteristic disease that occurs primarily in adulthood. Men are slightly more likely to be affected. The etiopathogenesis that leads to the transformation of the keratinocytes remains unclear; associations with genetic mutations and trigger factors such as UV rays and immunosuppression were observed. Due to the risk of malignant degeneration, consistent sun protection and regular clinical controls should take place. Cryotherapy, ablative laser therapy, curettage, photodynamic therapy or topical application of fluorouracil (5-FU), imiquimod and retinoids can be used to treat itchy, painful or cosmetically disturbing porokeratoses, depending on the location and severity.

Topical simvastatin-cholesterol for disseminated superficial actinic porokeratosis: An open-label, split-body clinical trial

BACKGROUND/OBJECTIVES

Disseminated superficial actinic porokeratosis (DSAP) is a porokeratosis variant that is cosmetically disfiguring and may be associated with squamous cell carcinoma. It is an autosomal dominant condition caused by germline mutations in mevalonate pathway genes involved in cholesterol synthesis. Lesions are precipitated by ultraviolet radiation-induced second-hit mutations. Modulation of this pathway by topical simvastatin-cholesterol may lead to improvement.

METHODS

This open-label, split-body clinical trial was carried out in 2020 at a metropolitan dermatology clinic. Eight patients contributing 13 limb pairs were recruited. Limbs within each pair were randomly allocated to 2% simvastatin/2% cholesterol cream applied twice daily or bland emollients. Lesion number, erythema, scale and patient-reported disease activity were measured at baseline and 6 weeks. Data were analysed using Bayesian ordinal logistic regression. Odds ratios compare the odds of a higher score at 6 weeks in treated limbs with the odds in controls. Values less than one indicate improvement.

RESULTS

Patients had a median age of 65 years (interquartile range [IQR] 58 to 69 years). The median baseline DLQI was 5 (range 2-21). Odds ratios were 0.12 (95% credible interval [CI] 0.01 to 0.72) for lesion number, 0.25 (95% CI 0.05 to 0.79) for erythema score, 0.18 (95% CI 0.03 to 0.64) for scale score and 0.33 (95% CI 0.09 to 0.89) for patient-reported disease activity.

CONCLUSIONS

Topical simvastatin-cholesterol cream improved lesion number, erythema and scale on treated limbs compared with controls. Patient-reported disease activity also improved. These findings warrant confirmation in blinded, vehicle-controlled trials.

Mevalonate Kinase-Associated Diseases: Hunting for Phenotype-Genotype Correlation

Mevalonate kinase-associated diseases (MKAD) are caused by pathogenic mutations in the mevalonate kinase gene (MVK) and encompass several phenotypically different rare and hereditary autoinflammatory conditions. The most serious is a recessive systemic metabolic disease called mevalonic aciduria, and the most recently recognized is disseminated superficial actinic porokeratosis, a dominant disease limited to the skin. To evaluate a possible correlation between genotypes and (1) the different MKAD clinical subtypes or (2) the occurrence of severe manifestations, data were reviewed for all patients with MVK variants described in the literature (N = 346), as well as those referred to our center (N = 51). The genotypes including p.(Val377Ile) (homozygous or compound heterozygous) were more frequent in mild systemic forms but were also sometimes encountered with severe disease. We confirmed that amyloidosis was more prevalent in patients compound heterozygous for p.(Ile268Thr) and p.(Val377Ile) than in others and revealed new associations. Patients homozygous for p.(Leu264Phe), p.(Ala334Thr) or compound heterozygous for p.(His20Pro) and p.(Ala334Thr) had increased risk of severe neurological or ocular symptoms. All patients homozygous for p.(Leu264Phe) had a cataract. The variants associated with porokeratosis were relatively specific and more frequently caused a frameshift than in patients with other clinical forms (26% vs. 6%). We provide practical recommendations focusing on phenotype-genotype correlation in MKAD that could be helpful for prophylactic management.

The Malignancy Potential of Porokeratosis: A Single-Center Retrospective Study

Background Porokeratosis (PK) is a rare group of keratinization disorders. While the overall prognosis of PK is favorable, malignant transformation of PK to skin cancer has been reported in 6.9% to 11.6% of the cases. Prior estimates of malignant transformation of PK have been based on reviews of published cases, which introduces possible publication bias. We aim to eliminate this potential bias and quantify the characteristics, risk factors, and malignancy potential of PK. Methodology A single-center retrospective chart review of patients with a diagnosis of PK was conducted. Results In this study, 6.4% to 16.4% of histologically confirmed PK lesions demonstrated malignant transformation. A higher proportion of disseminated superficial actinic porokeratosis (DSAP) cases (as high as 29.3%) showed malignant transformation compared to PK of Mibelli (as high as 6.0%). Out of the two cases of linear PK, both demonstrated malignant transformation. Conclusions In summary, PKs are at risk for malignant transformation, and patients with DSAP and linear PK, in particular, should receive more long-term surveillance. Limitations of this study include the inability to control for confounding factors due to the retrospective nature and the small size of our cohort.

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.

Disseminated Superficial Actinic Porokeratosis in the Elderly: A Case Report

Currently, most authors believe that disseminated superficial actinic porokeratosis (DSAP) is an inherited or acquired dermatologic disorder of keratinization that occurs in genetically predisposed individuals after adequate exposure to ultraviolet (UV) rays, or immunosuppression. Lesions in DSAP start in sun-exposed areas most commonly in the third or fourth decade of life. The lesions are pink to brownish papules and plaques with a raised scaling ridge, histologically seen as a column of parakeratotic keratinocytes, the cornoid lamella. DSAP is not only the most common, but also the most often overlooked form of porokeratosis (P). Here we present a 77-year-old male with DSAP, who sporadically developed initial skin lesions at the age of 67, at the time when his personal and medical history were significantly long for chronic intensive sun exposure and type 1 insulin dependent diabetes mellitus. We established the diagnosis of DSAP based on personal and medical history, clinical presentation, auxiliary methods such as dermoscopy, and confirmed with pathohistological findings. We advised the patient to avoid sun exposure and to apply photo-protective sunscreens, emollients and keratolytics. After five years of monitoring his changes, we continue to control his lesions for any possible alteration. Although mutations in several genes and data on sun exposure may be responsible for the onset of the disease, most cases of DSPA occur sporadically and without involving the facial skin, as in our case. Lesions usually begin in the third or fourth decade of life. In the elderly, an additional trigger may be present, such as e.g. age-related decreased immune competence. Diabetes mellitus may also be associated with immunodeficiency in the elderly. Recently, DSPA has been a special subtype of DSPA in the elderly. Malignant alteration can occur in DSPA, most commonly in lesions that are long lasting, large, in the elderly, or in lesions in immunocompromised individuals. In conclusion, this is the case of a 77-year-old male person, who sporadically developed the so-called subtype DSPA in the elderly. In addition to UV radiation, the relevant suggestive trigger factors were the immunosuppressive effects of diabetes mellitus and chronological aging.

Porokeratosis: A Review of Its Pathophysiology, Clinical Manifestations, Diagnosis, and Treatment

Porokeratosis comprises a group of heterogeneous and uncommon acquired or congenital skin diseases of unknown origin characterized by a keratinization disorder resulting from abnormal clonal expansion of keratinocytes. Numerous genetic mutations are thought to be involved. These conditions are characterized histologically by the presence of a cornoid lamella. Clinical manifestations are variable, with localized, disseminated, and even eruptive forms. Porokeratosis has been associated with immunosuppression, ultraviolet radiation, and systemic, infectious, and neoplastic diseases. Many authors consider it to be a premalignant condition because of the potential for malignant transformation to squamous cell or basal cell carcinoma. Therefore, long-term follow-up is a key component of treatment, which is usually complex and often unsatisfactory. We review the latest advances in our understanding of the pathogenesis, diagnosis, and treatment and propose a treatment algorithm.

Second-Hit, Postzygotic PMVK and MVD Mutations in Linear Porokeratosis

Importance

Linear porokeratosis features linear and whorled configurations of keratotic papules and plaques, with coronoid lamellae present on histologic examination. Because linear porokeratosis manifests in the lines of Blaschko representing the dorsoventral migration patterns of keratinocyte precursors, it has been suggested that postzygotic somatic mutation underlies the disease. However, no genetic evidence has supported this hypothesis to date.

Objective

To identify genetic mutations associated with linear porokeratosis.

Design, Setting, and Participants

Paired whole-exome sequencing of affected skin and blood/saliva samples from 3 participants from 3 academic medical centers with clinical and histologic diagnoses of linear porokeratosis.

Interventions or Exposures

Whole-exome sequencing of paired blood/saliva and affected tissue samples isolated from linear porokeratosis lesions.

Main Outcomes and Measures

Germline and somatic genomic characteristics of participants with linear porokeratosis.

Results

Of the 3 participants, 2 were male. Participant ages ranged from 5 to 20 years old. We found a combination of a novel germline mutation and a novel somatic mutation within affected tissue in all cases. One participant had a germline heterozygous PMVK c.329G>A mutation and a somatic copy-neutral loss of heterozygosity confined to the lesional skin, while a second had a germline heterozygous PMVK c.79G>T mutation and an additional PMVK c.379C>T mutation in the lesional skin. In a third participant, there was a germline splice-site mutation in MVD (c.70 + 5G>A) and a somatic deletion in MVD causing frameshift and premature codon termination within the lesional skin (c.811_815del, p.F271Afs*33 frameshift).

Conclusions and Relevance

Our findings suggest that linear porokeratosis is associated with the presence of second-hit postzygotic mutations in the genes that encode enzymes within the mevalonate biosynthesis pathway, and provide further evidence that the mevalonate pathway may be a potential target for therapeutic intervention in porokeratosis.

Squamous cell carcinoma arising from giant porokeratosis and rare postoperative recurrence and metastasis: A case report

RATIONALE

Giant porokeratosis is considered to be a variant of porokeratosis of Mibelli (PM) by some medical scholars. Porokeratosis can develop into several epidermal malignant tumors, such as Bowen disease and basal cell carcinoma, among which squamous cell carcinoma (SCC) is the most common.

PATIENT CONCERNS

The patient was a 53-year-old man who was admitted to our hospital due to postoperative recurrence and metastasis as SCC arising from giant PM in his left leg and foot.

DIAGNOSES

The pathological results are porokeratosis and well-differentiated squamous cell carcinoma. Positron emission tomography and computed tomography results show the local recurrence of the tumor with multiple lymph node metastasis.

INTERVENTIONS

This patient was transferred to orthopedic surgery for amputation of the middle and lower left thigh.

OUTCOMES

Follow-up for 3 months has shown no recurrence after the surgery.

LESSONS

This report reminds us to pay close attention to the likelihood of giant porokeratosis. The physicians should explore all clinical possibilities to avoid misdiagnosis of this rare disease.Although the recurrence rate of SCC arising from giant PM is very low, the surgical resection region should be expanded appropriately such as the en-block resection.

p63 Is a Promising Marker in the Diagnosis of Unusual Skin Cancer

Skin cancer is the most common type of cancer worldwide. Ozone depletion and climate changes might cause a further increase in the incidence rate in the future. Although the early detection of skin cancer enables it to be treated successfully, some tumours can evolve and become more aggressive, especially in the case of melanoma. Therefore, good diagnostic and prognostic markers are needed to ensure correct detection and treatment. Transcription factor p63, a member of the p53 family of proteins, plays an essential role in the development of stratified epithelia such as skin. In this paper, we conduct a comprehensive review of p63 expression in different types of skin cancer and discuss its possible use in the diagnosis and prognosis of cutaneous tumours.

Clonal Expansion of Second-Hit Cells with Somatic Recombinations or C>T Transitions Form Porokeratosis in MVD or MVK Mutant Heterozygotes

Patients with disseminated superficial actinic porokeratosis (DSAP) and linear porokeratosis (LP) exhibit monoallelic germline mutations in genes encoding mevalonate pathway enzymes, such as MVD or MVK. Here, we showed that each skin lesion of DSAP exhibited an individual second hit genetic change in the wild-type allele of the corresponding gene specifically in the epidermis, indicating that a postnatal second hit triggering biallelic deficiency of the gene is required for porokeratosis to develop. Most skin lesions exhibited one of two principal second hits, either somatic homologous recombinations rendering the monoallelic mutation biallelic or C>T transition mutations in the wild-type allele. The second hits differed among DSAP lesions but were identical in those of congenital LP, suggesting that DSAP is attributable to sporadic postnatal second hits and congenital LP to a single second hit in the embryonic period. In the characteristic annular skin lesions of DSAP, the central epidermis featured mostly second hit keratinocytes, and that of the annular ring featured a mixture of such cells and naïve keratinocytes, implying that each lesion reflects the clonal expansion of single second hit keratinocytes. DSAP is therefore a benign intraepidermal neoplasia, which can be included in the genetic tumor disorders explicable by Knudson's two-hit hypothesis.

Squamous Cell Carcinoma Arising from Linear Porokeratosis - a case report and review of the literature

Porokeratosis belongs to a group of disorders of keratinization that are characterized by the histopathological feature of the cornoid lamella, a column of tightly fitted parakeratotic cells. The etiology of porokeratosis is still unclear. Different variants of porokeratosis (PK) have been subsequently recognized, each with its own specific properties in terms of morphology, distribution and clinical course. Linear porokeratosis is one of the variants of porokeratosis, a rare disorder of keratinization that may develop into several epidermal malignancies, squamous cell carcinoma being the most frequent among all of them. Thus, a clinical surveillance for malignancy is an imperative. We present a case of a 54-year-old man with non-healing ulcer of the lower leg caused by squamous cell carcinoma arising on long-standing linear porokeratosis. The treatment included wide excision of tumor with the reconstruction of the area. Acitretin was prescribed for linear porokeratosis treatment. The follow-up of our patient so far has shown that he does not have new malignant lesions after surgical excision.

Pediatric penile porokeratosis: A case report

We present what we believe to be the second case of pediatric penile porokeratosis and the youngest case reported. A 6-year-old boy presented with a pruritic, verrucous growth at the urethral meatus that recurred after two meatotomies. The diagnosis of porokeratosis was confirmed by biopsy. Porokeratosis should be added to the differential diagnosis of chronic hyperkeratotic penile lesions in children.

Amelanotic melanoma arising within a lesion of disseminated superficial actinic porokeratosis: An unusual presentation leading to a novel therapeutic approach

Disseminated superficial actinic porokeratosis (DSAP) is the most common variant of porokeratosis with a potential for malignant transformation. Its association with malignant melanoma, however, is exceedingly rare. Treatment of DSAP is often ineffective. We report a unique case of amelanotic melanoma arising within a lesion of DSAP. The melanoma was managed surgically, and her DSAP were treated successfully with a novel approach utilizing 5-fluorouracil chemowraps.

Treatment of Porokeratosis: A Systematic Review

BACKGROUND

Porokeratosis (PK) is a rare skin disease of unknown etiology. It consists of a keratinization disorder, which may appear in several clinical forms and can undergo malignant transformation. The histopathological hallmark of PK is the cornoid lamella. While many topical, systemic, and surgical treatment modalities for PK have been described, no randomized controlled trials have been performed yet. Because of a lack of treatment standards for PK, European and international guidelines cannot be created.

OBJECTIVE

The aim of this systematic review is to outline options for treating PK.

METHODS

We performed a systematic literature search in an electronic database for published literature. A total of 88 articles fulfilling our inclusion criteria were found.

RESULTS

There were no randomized controlled trials on the treatment of PK, but mainly case reports and case series. Porokeratosis of Mibelli showed the best outcomes after treatment with imiquimod cream and linear PK responded well to topical or systemic retinoids. Topical vitamin D acid derivatives may be the best therapeutic option for disseminated PK. Surgical interventions and cryotherapy may be preferred in areas where the use of topical agents is difficult or contraindicated.

CONCLUSION

To offer patients with PK an evidence-based high-quality standardized therapy, randomized controlled trials are needed.

Porokeratosis of Mibelli in an HIV-positive patient

Porokeratosis represents a group of disorders of epidermal keratinization that are characterized by one or more annular plaques surrounded by a histologically distinctive hyperkeratotic ridge-like border called the cornoid lamella. Many studies showed that organ transplantation and immunosuppression were associated in a significant number of cases. Furthermore, an association with squamous cell carcinoma and basal cell carcinoma has been noted in all variants of porokeratosis. The rarity of this disorder and its atypical clinical presentation – a single lesion on the thumb of an HIV-positive male patient – motivated this report.

'Hints' in the horn: diagnostic clues in the stratum corneum

The stratum corneum or horny layer is the uppermost layer of the epidermis, and is mainly responsible for the skin's barrier function. In spite of its complexity at the ultrastructural and molecular level, the features accessible to visualization on conventional histology are relatively limited. Nevertheless, knowledge of subtle clues that one may observe in the stratum corneum can prove useful in a wide range of situations in dermatopathology. We herein review a selection of common and rare entities in which the horny layer may reveal significantly important hints for the diagnosis. These clues include parakeratosis and its different patterns (focal, confluent, alternating, associated with spongiosis, epidermal hyperplasia or lichenoid changes), subcorneal acantholysis, infectious organisms in the stratum corneum (including fungal, bacterial and parasitic), thickening or thinning of the stratum corneum and the presence of different kinds of pigment. Even when normal, the horny layer may prove to be useful when seen in association with severe epidermal damage, a combination of features testifying to the acute nature of the underlying pathological process.

Loss-of-function Mutation in PMVK Causes Autosomal Dominant Disseminated Superficial Porokeratosis

Disseminated superficial porokeratosis (DSP) is a rare keratinization disorder of the epidermis. It is characterized by keratotic lesions with an atrophic center encircled by a prominent peripheral ridge. We investigated the genetic basis of DSP in two five-generation Chinese families with members diagnosed with DSP. By whole-exome sequencing, we sequencing identified a nonsense variation c.412C > T (p.Arg138*) in the phosphomevalonate kinase gene (PMVK), which encodes a cytoplasmic enzyme catalyzing the conversion of mevalonate 5-phosphate to mevalonate 5-diphosphate in the mevalonate pathway. By co-segregation and haplotype analyses as well as exclusion testing of 500 normal control subjects, we demonstrated that this genetic variant was involved in the development of DSP in both families. We obtained further evidence from studies using HaCaT cells as models that this variant disturbed subcellular localization, expression and solubility of PMVK. We also observed apparent apoptosis in and under the cornoid lamella of PMVK-deficient lesional tissues, with incomplete differentiation of keratinocytes. Our findings suggest that PMVK is a potential novel gene involved in the pathogenesis of DSP and PMVK deficiency or abnormal keratinocyte apoptosis could lead to porokeratosis.