Follicular porokeratosis: four new cases.

Porokeratosis, a disorder of keratinisation, is clinically characterized by the presence of annular plaques with a surrounding keratotic ridge. Clinical variants include linear, disseminated superficial actinic, verrucous/hypertrophic, disseminated eruptive, palmoplantar and porokeratosis of Mibelli (one or two typical plaques with atrophic centre and guttered keratotic rim). All of these subtypes share the histological feature of a cornoid lamella, characterized by a column of 'stacked' parakeratosis with focal absence of the granular layer, and dysmaturation (prematurely keratinised cells in the upper spinous layer). In recent years, a proposed new subtype, follicular porokeratosis (FP_, has been described, in which the cornoid lamella are exclusively located in the follicular ostia. We present four new cases that showed typical histological features of FP.

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.

Porokeratosis ptychotropica: a rare and evolving variant of porokeratosis.

Porokeratosis ptychotropica represents a rare and under-recognized variant of porokeratosis. There are also alternative descriptions for this disorder in the literature. Since its original description in 1995, additional characteristic features have been showed in case reports published in the literature. These cumulative reports, although still limited in numbers, have helped to further shape and define this entity. A case report and review of published literature on this unusual entity are presented. The specific combination of clinical, morphological and histopathological characteristics that can facilitate recognition of the disorder is discussed. There has been a call for uniformity in terminology and a suggestion for alternative terminology has been made. However, we discuss why the earlier term, porokeratosis ptychotropica, is still preferred.

Mibelli revisited: a case of type 2 segmental porokeratosis from 1893.

In autosomal dominant skin disorders, a pronounced mosaic involvement may sometimes be found to be superimposed on the ordinary nonsegmental lesions. Such "type 2 segmental manifestation" reflects loss of heterozygosity occurring at an early developmental stage, giving rise to a cell clone that lacks the corresponding wild-type allele. Here, this genetic concept is applied to an unusual case of plaque-type porokeratosis of Mibelli (PM) as published in 1893 by Vittorio Mibelli in the International Atlas of Rare Skin Diseases. The right forearm and hand of the 21-year-old patient showed a pronounced linear porokeratosis that had developed since the age of 2 years. Moreover, nonsegmental lesions of PM involved both hands and forearms as well as the face and the neck, having first been noticed at the age of 7 years. Two siblings and the father were likewise affected with PM. Hence, Mibelli's case from 1893 meets all of the criteria of a type 2 segmental manifestation of an autosomal dominant skin disorder. Recognizing such cases of superimposed segmental involvement may help elucidate the molecular basis of PM.

Disseminated superficial actinic porokeratosis co-existing with linear and verrucous porokeratosis in an elderly woman: Update on the genetics and clinical expression of porokeratosis.

Disseminated superficial actinic porokeratosis (DSAP) is the most common form of porokeratosis, occurring mainly in women on the extremities as atrophic patches rimmed by a ridge of keratin (the cornoid lamella that is diagnostic of porokeratosis histologically and is thought to be a clonal keratinocyte proliferation). DSAP can sometimes coexist with other forms of porokeratosis (Mibelli, linear porokeratosis, porokeratosis palmaris et plantaris disseminata, and punctate porokeratosis). Rare variants of linear porokeratosis are the hyperkeratotic and verrucous forms which usually occur on the buttocks or perianal area. We present clinical and histopathologic findings from biopsy specimens of a 73-year-old woman with DSAP on the distal extremities, linear/segmental porokeratosis on thighs, and verrucous porokeratosis on buttocks and mons pubis. The verrucous lesions had been present for 30+ years, the DSAP and linear lesions for 10+ years. Biopsy specimens from distal extremity showed classic features of DSAP with infrequent cornoid lamellae separated by atrophic epidermis. Biopsy specimens from the mons pubis and thigh showed epidermal hyperplasia with multiple, almost contiguous, broad cornoid lamellae. Coexisting variants of porokeratosis are rare and our conclusions are drawn from a few cases in the literature. The rare variants of porokeratosis are of interest because the clinical morphology correlates with the histopathology.

Generalized type 2 segmental disseminated superficial actinic porokeratosis coexisted with multiple cutaneous squamous cell carcinomas: Analysis of two cases.

Porokeratosis (PK) is defined as hyperpigmented macules or patches with a distinctive, ridge-like hyperkeratotic border which is histologically characterized by a cornoid lamella. Here, we report two cases of linear porokeratosis which converted to multiple cutaneous squamous cell carcinoma after long history progression. In addition, patient 2 was accompanied by secondary dermal amyloid deposits, which was rare reported.

Porokeratosis ptychotropica: a clinically distinct variant of porokeratosis.

Porokeratosis represents a spectrum of clinical disease. Multiple variants have been described including porokeratosis ptychotropica, a rare subtype. The clinical presentation of porokeratosis ptychotropica frequently resembles an inflammatory perianal disease. We report a patient with porokeratosis ptychotropica with coexistent disseminated superficial actinic porokeratosis. We review the current literature on porokeratosis ptychotropica including the clinical presentation, histopathology, cause, and pathogenesis of this rare variant of porokeratosis.

Widespread porokeratotic adnexal ostial nevus: clinical features and proposal of a new name unifying porokeratotic eccrine ostial and dermal duct nevus and porokeratotic eccrine and hair follicle nevus.

Porokeratotic eccrine ostial and dermal duct nevus and a similar condition, porokeratotic eccrine and hair follicle nevus, are rare disorders of keratinization with eccrine and hair follicle involvement. We describe the clinical features in 5 patients, all of whom had widespread skin involvement following the lines of Blaschko. Two patients presented with erosions in the newborn period as the initial manifestation of their disease; one had an associated structural anomaly, unilateral breast hypoplasia; and one adult had malignant transformation in the nevus with development of multifocal squamous cell carcinomas. Three patients had histologic involvement of both acrosyringia and acrotrichia. Based on the observation of overlapping histologic features, we propose the name "porokeratotic adnexal ostial nevus" to incorporate the previously described entities porokeratotic eccrine ostial and dermal duct nevus and porokeratotic eccrine and hair follicle nevus.

Porokeratosis ptychotropica: a lesser-known variant.

We report a case of the rare porokeratosis variant porokeratosis ptychotropica (PP). A circumferential perianal plaque and the characteristic histology of multiple cornoid lamellae with underlying dermal amyloid deposition were seen. Amyloid deposition was seen in the biopsied intertriginous area of the plaque only, which, in concordance with other cutaneous amyloid deposition disorders, may suggest a role for friction in the pathogenesis of this histological finding. We review the literature on PP and summarize the poor response seen to treatments.

Type 2 segmental manifestation of disseminated superficial porokeratosis showing a systematized pattern of involvement and pronounced cancer proneness.

Nine tumors of squamous cell carcinoma developed in a 61-year-old Japanese woman with linear porokeratosis. She had disseminated superficial porokeratosis, but a linear arrangement of pronounced lesions was found only on the left side of the body, and all of the tumors arose on the linear lesions on the left side of the body. Some of her family members had disseminated superficial porokeratosis. This case may represent a type 2 segmental manifestation of disseminated superficial porokeratosis showing a systematized pattern of involvement and pronounced cancer proneness.

Cornoid lamellae associated with follicular infundibulum and acrosyringium in porokeratosis.

Skin lesions of porokeratosis consist of an atrophic center bordered by a peripheral grooved keratotic ridge that corresponds histopathologically to the cornoid lamella. Originally porokeratosis was named based on the assumption that the columns of parakeratosis emerge from the ostia of eccrine ducts. Despite this, it is generally accepted that the cornoid lamellae are rarely related to the acrosyringium. We recently encountered two cases of porokeratosis, where the cornoid lamellae were related to the follicular infundibulums. Therefore, we analyzed the location of the cornoid lamellae in 86 lesions of porokeratosis from 73 patients from our archives. We found that many cornoid lamellae are also detected at follicular infundibulum and acrosyringium. The existence of so many cornoid lamellae at follicular infundibulum and acrosyringium inside the plaques cannot be explained by pure coincidence and may be more than fortuitous.

Porokeratosis in the elderly: a new subtype of disseminated superficial actinic porokeratosis.

In a review of all cases of porokeratosis histologically diagnosed in our Department during the period 1991-98 we found that 12 patients (22%) were in their seventh to ninth decade. In all 12 (2 males and 10 females) the age of onset of the disease varied between 58 and 89 years (mean age 68.6 years). The clinical picture was similar in all the patients, with the number of lesions varying from a few to 20-50 annular plaques 10-15 mm in diameter, localized mainly on the lower limbs. We suggest that our patients had a very mild form of disseminated superficial actinic porokeratosis confined to the extremities with an unusually late onset. This peculiar variety of late-onset disseminated superficial actinic porokeratosis may represent a type of immunosuppression-induced porokeratosis where the pathologic clone for porokeratosis is present but remains latent until the amount of sun exposure, together with the physiological age-related lowering of immunocompetence, bring about its proliferation.

The hyperkeratotic variant of porokeratosis Mibelli is a distinct entity: clinical and ultrastructural evidence.

An isolated case with the hyperkeratotic variant of porokeratosis Mibelli (PM) is reported. The 62-year-old woman developed multiple brown macules with well demarcated large keratotic nodules on both legs. Histopathological studies revealed the presence of a cornoid lamella characteristic of porokeratosis. Ultrastructural investigations revealed dyskeratotic as well as edematous, swollen keratinocytes; autophagocytotic vacuoles were visible. The clinical and ultrastructural peculiarities of the hyperkeratotic variant of PM suggest the possibility of a separate entity.

Cancer proneness of linear porokeratosis may be explained by allelic loss.

BACKGROUND: It is well known that porokeratosis, a genetically heterogeneous disorder characterized by the histopathological feature of the cornoid lamella, shows an increased proneness to develop carcinoma. On the other hand, a significant mechanism in the origin of many forms of cancer is loss of heterozygosity or allelic loss. OBJECTIVE: Because it has recently been proposed that linear porokeratosis may result from allelic loss, one might expect that linear porokeratosis is especially prone to malignant degeneration. In order to test this hypothesis, a review of case reports was performed. METHOD: Cases of cancer-associated porokeratosis were collected from the European language literature and assigned to one of 5 different types [plaque type of Mibelli (PM); disseminated actinic superficial porokeratosis (DSAP); porokeratosis palmaris, plantaris et disseminata (PPPD); porokeratosis punctata palmaris et plantaris (PPPP); linear porokeratosis (LP)]. RESULTS: Malignant or premalignant lesions were reported in 9 cases of PM, 15 cases of DSAP, 3 cases of PPPD, 1 case of PPPP and 21 cases of LP. CONCLUSION: This analysis supports the view that among the various forms of porokeratosis, the linear type is particularly susceptible to malignant degeneration. Arguments are presented in favor of the assumption that the genetic mechanism of allelic loss giving rise to LP may represent an initial step in the development of cancer.