Disseminated superficial actinic porokeratosis with both typical and prurigo nodularis-like lesions

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.

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.

Porokeratosis: An enigma beginning to unravel

Porokeratosis is a keratinization disorder with unclear etiopathogenesis, varied clinical presentation and characteristic histopathology, and is usually unresponsive to current therapeutic options. Until now, it was considered to be a clonal disorder with immunity, ultra violet radiation and other factors playing important roles in etiopathogenesis. It is now known that abnormalities in the mevalonate pathway are responsible for this clonal keratinization abnormality. New variants of porokeratosis like eruptive bullous, pruriginous, lichen planus like, follicular variants and porokeratoma have been described. While the cornoid lamella is the classical histopathologic feature, dermoscopy and reflectance confocal microscopy make the diagnosis clearer. Development of malignancy in a few variants is a concern. Linear, disseminated superficial actinic and giant lesions are most prone to developing malignancies. Bowen's disease, squamous cell carcinoma, basal cell carcinoma and even melanoma have been reported in cases of long-standing porokeratosis. Newer modalities of therapy such as photodynamic therapy, ingenol mebutate and HMGCoA inhibitors may play a role in the future.

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.

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.

Eruptive pruritic papular porokeratosis: A pruritic variant of porokeratosis

Porokeratosis is a chronic skin disorder characterized clinically by the presence of crater-like patches with an elevated thick keratotic border and central atrophy. Histology reveals cornoid lamellae. While porokeratosis is practically asymptomatic, a pruritic variant has been reported. We recently encountered an 82-year-old man with pruritic porokeratosis. He presented with erythematous papules and intensively itchy patches on his lower limbs that had been present for 6 months. Histopathological examination revealed the characteristic cornoid lamellae. We describe this case in detail and provide a review of the published work.

A novel locus (DSAP2) for disseminated superficial actinic porokeratosis maps to chromosome 15q25.1-26.1

BACKGROUND

Disseminated superficial actinic porokeratosis (DSAP) is a chronic cutaneous disorder characterized by multiple superficial keratotic lesions surrounded by a slightly raised keratotic border. It develops in teenagers in sun-exposed areas of skin and usually follows an autosomal dominant inheritance pattern. The first locus for DSAP was localized to chromosome 12q23.2-24.1, but no gene responsible for porokeratosis has been identified to date.

OBJECTIVES

To determine whether DSAP is a genetically heterogeneous disorder and to identify the disease gene locus in a three-generation Chinese family with DSAP.

METHODS

Genetic linkage analysis was carried out in this family using 15 microsatellite markers between D12S1671 and D12S369 on chromosome 12q, followed by a genome-wide scan with 382 microsatellite markers from the autosomes.

RESULTS

Genetic linkage analysis with chromosome 12q markers suggested that the locus in this family is not linked to chromosome 12q. A genome-wide scan and fine mapping finally localized the locus for DSAP in this family to a 6.4-cM region between markers D15S1023 and D15S1030 at chromosome 15q25.1-26.1. This DSAP locus was named DSAP2.

CONCLUSIONS

The previous results and this study have shown that DSAP is a genetically heterogeneous disorder; a novel locus for DSAP, termed DSAP2, was mapped to a 6.4-cM region between markers D15S1023 and D15S1030.