Parakeratosis

VAMP2 controls murine epidermal differentiation and carcinogenesis by regulation of nucleophagy

Differentiation of murine epidermal stem/progenitor cells involves the permanent withdrawal from the cell cycle, the synthesis of various protein and lipid components for the cornified envelope, and the controlled dissolution of cellular organelles and nuclei. Deregulated epidermal differentiation contributes to the development of various skin diseases, including skin cancers. With a genome-wide shRNA screen, we identified vesicle-associated membrane protein 2 (VAMP2) as a critical factor involved in skin differentiation. Deletion of VAMP2 leads to aberrant skin stratification and enucleation in vivo. With quantitative proteomics, we further identified an autophagy protein, focal adhesion kinase family interacting protein of 200 kDa (FIP200), as a binding partner of VAMP2. Additionally, we showed that both VAMP2 and FIP200 are critical for murine keratinocyte enucleation and epidermal differentiation. Loss of VAMP2 or FIP200 enhances cutaneous carcinogenesis in vivo. Together, our findings identify important molecular mechanisms underlying epidermal differentiation and skin tumorigenesis.

The Role of Aryl Hydrocarbon Receptor in the Pathogenesis and Treatment of Psoriasis

The pathogenesis of psoriasis is complex. Aryl hydrocarbon receptor (AhR) is a transcription factor that can be bound and activated by structurally diverse ligands and plays an important role in a range of biological processes and in the pathogenesis of different diseases. Recently, the role of AhR in psoriasis has attracted attention. AhR has toxicological functions and physiological functions. The overexpression and activation of AhR induced by the environmental pollutant and exogenous AhR agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) can drive the development of psoriasis. This TCDD-mediated toxicological response disrupts the physiological functions of AhR resulting in skin barrier disorders and the release of inflammatory cytokines, 2 of the pivotal factors of psoriasis. In addition, highly upregulated kynureninase in psoriasis decreases endogenous AhR agonists, thereby weakening the physiological functions of AhR. Activating AhR physiological signalling should be useful in the treatment of psoriasis. Studies have demonstrated that physiological activation of AhR can dampen the severity of psoriasis. The oldest and effective treatment for psoriasis coal tar works by activating AhR, and both new anti-psoriasis drugs tapinarof and benvitimod are formulations of AhR agonist, supporting that activation of AhR can be used as a new strategy for the treatment of psoriasis. Preclinical and preliminary clinical studies have revealed the anti-psoriasis effects of a number of AhR agonists, providing potential candidates for the development of new drugs for the treatment of psoriasis.

Early concentrate starter introduction induces rumen epithelial parakeratosis by blocking keratinocyte differentiation with excessive ruminal butyrate accumulation

INTRODUCTION

Rumen epithelial parakeratosis, a common disease in ruminants caused by abnormalities in the ruminal stratified squamous epithelial keratinization process, negatively impacts ruminant health and performance. However, we still lack a comprehensive perception of the underlying mechanisms and the predisposing factors for this disorder.

OBJECTIVES

Here, we investigated rumen epithelial cell heterogeneity, differentiation trajectories, and cornification to clarify the rumen epithelial keratinization process and discern the key ruminal metabolites contributing to rumen epithelial parakeratosis.

METHODS

Twenty-four 14-day-old lambs were divided into three groups, including only milk feeding, milk plus alfalfa hay feeding, and milk plus corn-soybean concentrate starter feeding. At 42 days of age, the lambs were slaughtered, and rumen tissues were collected for single-cell RNA-sequencing (scRNA-seq), immunofluorescence, and quantitative real-time PCR (qRT-PCR) analyses. Ruminal fluid samples were collected for metabolomic analyses. Rumen epithelial organoid was used to verify the key ruminal metabolites contributing to parakeratosis.

RESULTS

As expected, we observed that concentrate starter introduction resulted in rumen epithelial parakeratosis. Moreover, scRNA-seq analysis revealed a developmental impediment in the transition from differentiated keratinocytes to terminally differentiated keratinocytes (TDK) in lambs with concentrate starter introduction. Immunofluorescence and qRT-PCR analyses further verified the location and expression of marker genes of TDK. Metabolomic analysis showed a robust positive correlation between ruminal butyrate levels and rumen epithelial keratinization. More importantly, we successfully established a rumen organoid model capable of facilitating the study of the keratinization process in the rumen epithelia and further confirmed that high dose butyrate indeed contributed to rumen epithelial parakeratosis.

CONCLUSION

Collectively, concentrate starter introduction induces ruminal epithelial parakeratosis by blocking keratinocyte differentiation with excessive ruminal butyrate accumulation in a neonatal lamb model. These findings enhance our understanding of rumen epithelial keratinization and provide valuable insights for addressing rumen epithelial parakeratosis using early nutritional intervention strategies.

Eicosapentaenoic acid reduces the proportion of IL-17A-producing T cells in a 3D psoriatic skin model

Psoriasis is a skin disease presenting as erythematous lesions with accentuated proliferation of epidermal keratinocytes, infiltration of leukocytes, and dysregulated lipid metabolism. T cells play essential roles in the disease. n-3 polyunsaturated fatty acids are anti-inflammatory metabolites, which exert an immunosuppressive effect on healthy T cells. However, the precise mechanistic processes of n-3 polyunsaturated fatty acids on T cells in psoriasis are still unrevealed. In this study, we aimed to evaluate the action of eicosapentaenoic acid (EPA) on T cells in a psoriatic skin model produced with T cells. A coculture of psoriatic keratinocytes and polarized T cells was prepared using culture media, which was either supplemented with 10 μM EPA or left unsupplemented. Healthy and psoriatic skin substitutes were produced according to the self-assembly method. In the coculture model, EPA reduced the proportion of IL-17A-positive cells, while increasing that of FOXP3-positive cells, suggesting an increase in the polarization of regulatory T cells. In the 3D psoriatic skin model, EPA normalized the proliferation of psoriatic keratinocytes and diminished the levels of IL-17A. The expression of the proteins of the signal transducer and activator of transcription was influenced following EPA supplementation with downregulation of the phosphorylation levels of signal transducer and activator of transcription 3 in the dermis. Finally, the NFκB signaling pathway was modified in the EPA-supplemented substitutes with an increase in Fas amounts. Ultimately, our results suggest that in this psoriatic model, EPA exerts its anti-inflammatory action by decreasing the proportion of IL-17A-producing T cells.

Parakeratosis and pagetoid melanocytosis in the evaluation of dysplastic nevi and melanoma

BACKGROUND

It is our experience that parakeratosis with pagetosis is common in early melanoma when there is no history of trauma in the anatomical site. In lesions where the differential diagnosis includes dysplastic nevus (DN) and melanoma, we hypothesize that parakeratosis may be a marker for cases in which immunohistochemistry (IHC) may identify occult pagetosis.

METHODS

We performed a retrospective case-control study on cases with a histologic differential diagnosis of DN versus melanoma, including 423 cases with parakeratosis and 125 cases without parakeratosis. IHC staining (Mart-1 and/or Sox-10) was performed in all cases. The frequency of pagetosis and diagnostic upgrades in the cases versus the controls was calculated.

RESULTS

The presence of parakeratosis was significantly associated with pagetosis (p < 0.0001). Diagnostic upgrades were more frequent in the cases with parakeratosis versus controls without parakeratosis (p = 0.0029). In the favored moderate DN group, 56% of cases were upgraded compared to 30% of the controls (p = 0.0017). In the favored mild DN and severe DN groups, there were more case upgrades compared to the controls (p = 0.1386, p = 0.2738).

CONCLUSIONS

Parakeratosis may be a useful marker to identify lesions with occult pagetosis for which IHC would be appropriate and may result in a diagnostic upgrade.

Restoration of calcium-induced differentiation potential and tight junction formation in HaCaT keratinocytes by functional attenuation of overexpressed high mobility group box-1 protein

HaCaT cells have been widely used as undifferentiated epidermal keratinocytes, since these non-tumorigenic cells can be readily maintained in conventional medium and partly retain epidermal differentiation potential upon stimulation with high concentration of calcium. In contrast to primary epidermal keratinocytes, however, these cells never form tight junction (TJ), a specific structure in highly differentiated keratinocytes, solely by the differentiation stimulation. Here, we show that HaCaT cells secrete a considerable amount of high mobility group box-1 protein (HMGB1), one of major inflammatory mediator, which appeared to be responsible, at least in part, for such aberrant differentiation response. So far, inhibition of c-Jun N-terminal kinase (JNK) in high calcium medium has been supposed to be the only way to induce TJ formations in HaCaT cells; however, SP600125, a potent inhibitor of JNK showed cytostatic effects and clearly attenuated epidermal differentiation and stratification. In contrast, dipotassium glycyrrhizate (GK2), a soluble analogue of HMGB1-blocker Glycyrrhizin, down-regulated interferon-β, a typical inflammatory cytokine induced by secreted HMGB1, and accelerated differentiation responses to the calcium treatment in these cells. In addition, GK2-treatmenrt resulted in the formation of double cell layers in cultured HaCaT cells, where the stratified upper cells transiently accumulated TJ proteins at the cell-cell contact sites. These results highlight the importance of attenuation of secreted HMGB1-signals in cultured HaCaT cells for studies of functional keratinocytes.

Changes in epidermal morphology associated with dandruff

OBJECTIVE

Dandruff is a very common scalp condition characterized by flaking and pruritus usually with no visible signs of inflammation, such as redness and erythema. Dandruff is considered a multifactorial condition with both microbial colonization and host factors such as sebum production thought to play a role. There is evidence of changes in epidermal morphology in the scalp skin of dandruff sufferers, with reports of an increase in mean thickness and more nucleated cell layers. The underlying mechanisms driving these morphological changes are currently unclear. The objective of this study was to fully characterize epidermal morphology in dandruff compared to healthy scalp skin and to evaluate potential mechanisms underlying any changes observed.

METHODS

Scalp skin biopsies were taken from 22 healthy female subjects and 21 dandruff sufferers, from both lesional and non-lesional sites. Samples were processed, sectioned and stained using haematoxylin and eosin (H&E). To fully characterize epidermal morphology, measurements were taken of epidermal thickness, the convolution of the dermal-epidermal junction and the depth of epidermal rete ridges. To analyse changes in epidermal proliferation immunohistochemical staining was performed using Ki67, a well-established marker of cell proliferation, and quantified using image analysis.

RESULTS

Histochemical analysis of skin sections revealed that in dandruff lesional samples, the epidermis was thicker, had a more convoluted dermal epidermal junction and the rete ridges were elongated, compared to healthy scalp skin. Similar directional changes in epidermal morphology, were observed in non-lesional dandruff samples, albeit to a lesser extent. Image analysis of Ki67 expression in the epidermis revealed dandruff lesional skin contained significantly more Ki67-positive proliferating keratinocytes than healthy controls samples. This suggests dandruff scalp skin epidermal keratinocytes are in a hyper-proliferative state.

CONCLUSION

There were significant changes in epidermal morphology in dandruff lesional skin compared to healthy scalp skin including increased epidermal thickness, a more convoluted dermal-epidermal junction and elongation of rete ridges. Interestingly, we found there was evidence of an increase in the percentage of epidermal Ki67-positive cells, which has not been reported previously, and demonstrates dandruff is a condition displaying epidermal hyper-proliferation.

Biologics for the primary care physician: Review and treatment of psoriasis

Psoriasis is a chronic inflammatory disease that affects approximately 7.5 million people in the United States. The disease results in significant suffering, morbidity, and economic impact. Psoriasis is a multifaceted disease with a strong genetic component. Genetic data has revealed the presence of particular risk alleles in patients with psoriasis. Triggers of the disease have been elucidated and include factors such as trauma, obesity, infection, stress, and medications. At its core, psoriasis is a result of a dysfunctional immune response with T-cells at the center of immunogenesis. Clinically, psoriasis is characterized by discrete, erythematous scaly plaques. These lesions are often found on extensor surfaces, especially the elbows and knees. Although extensor surfaces are the prototypical destination of lesions, psoriasis may affect any area of the skin including the scalp, intertriginous areas, nails, palms, and soles. Location of lesions are important in assessing the impact on quality of life for patients. Diagnosis of psoriasis can typically be made clinically based on characteristic history and physical examination findings. In rare cases, biopsy may be needed to rule out other papulosquamous disease. Histologic findings of psoriasis can be non-specific and include marked epidermal hyperplasia, dilated vessels within the dermal papilla, and elongated rete ridges. Importantly, psoriasis is a systemic disease and organ systems outside of the skin must be considered. Co-morbidities of psoriasis include psoriatic arthritis, type 2 diabetes mellitus, cardiovascular disease, psychiatric disease, inflammatory bowel disease, neoplasms, and ocular disease. Management of psoriasis depends on the severity of the disease. In mild to moderate cases, topical medications are the cornerstone of treatment. Topical corticosteroids are the most commonly used and have limited systemic effects due to the localized application of medication. In moderate to severe cases of psoriasis, topical medications are ineffective and not feasible. Phototherapy and non-biologic systemic medications have been useful treatments; however, phototherapy is time consuming and non-biologic systemics have only modest response rates. In the last decade, biologic medications have become an important component of care for treating moderate to severe psoriasis. These medications target various cytokines responsible for psoriasis manifestations such as tumor necrosis factor (TNF-α), interleukin-12, interleukin-23, and interleukin-17. In the past 15 years, numerous biologic medications have been granted FDA approval, with the majority approved in the past several years. Some of the commonly used biologics include etanercept, adalimumab, infliximab, ixekizumab, secukinumab, brodalumab, guselkumab, ustekinumab, and tildrakizumab. Given the wealth of new biologics, current treatment guidelines have rapidly become outdated. This review provides summarized information of landmark trials that led to the approval of these medications.

Novel inflammatory cell infiltration scoring system to investigate healthy and footrot affected ovine interdigital skin

Ovine footrot is a degenerative disease of sheep feet leading to the separation of hoof-horn from the underlying skin and lameness. This study quantitatively examined histological features of the ovine interdigital skin as well as their relationship with pro-inflammatory cytokine (IL-1β) and virulent Dichelobacter nodosus in footrot. From 55 healthy and 30 footrot ovine feet, parallel biopsies (one fixed for histology) were collected post-slaughter and analysed for lesions and histopathological analysis using haematoxylin and eosin and Periodic Acid-Schiff. Histological lesions were similar in both conditions while inflammatory scores mirror IL-1β expression levels. Increased inflammatory score corresponded with high virulent D. nodosus load and was significant (p < 0.0001) in footrot feet with an inflammatory score of 3 compared to scores 1 and 2. In addition, in contrast to healthy tissues, localisation of eubacterial load extended beyond follicular depths in footrot samples. The novel inflammatory cell infiltration scoring system in this study may be used to grade inflammatory response in the ovine feet and demonstrated an association between severity of inflammatory response and increased virulent D. nodosus load.

Dnases in health and disease

DNA degradation is critical to healthy organism development and survival. Two nuclease families that play key roles in development and in disease are the Dnase1 and Dnase2 families. While these two families were initially characterized by biochemical function, it is now clear that multiple enzymes in each family perform similar, non-redundant roles in many different tissues. Most Dnase1 and Dnase2 family members are poorly characterized, yet their elimination can lead to a wide range of diseases, including lethal anemia, parakeratosis, cataracts and systemic lupus erythematosus. Therefore, understanding these enzyme families represents a critical field of emerging research. This review explores what is currently known about Dnase1 and Dnase2 family members, highlighting important questions about the structure and function of family members, and how their absence translates to disease.

'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.

Identification of an epidermal keratinocyte AMPA glutamate receptor involved in dermatopathies associated with sensory abnormalities

Supplemental Digital Content is Available in the Text.

This study presents the discovery of AMPA glutamate receptors in mouse and human epidermal keratinocytes and their potential role in the physiopathology of itch or pain.

Introduction: Epidermal keratinocytes are increasingly recognized as active participants in the sensory transduction of itch and pain, processes known to involve primary afferent glutamatergic neurons. However, the role of keratinocyte glutamate signaling in sensory functioning is not fully understood. Here, we present the observation of α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid–type glutamate receptors (AMPARs) in epidermal keratinocytes.

Methods: Immunohistochemical and in situ hybridization analyses were conducted to assess the expression of AMPAR subunits in epidermal keratinocytes in mouse and human skin samples, and in organotypic cultures of human keratinocytes. In addition, reverse transcription PCR further confirmed the expression of GluA4-containing AMPAR in epidermal keratinocytes.

Results: We found prominent immunolabeling for the GluA4 subunit of AMPAR in keratinocytes of glabrous and hairy skin of mouse epidermis, as well as in human epidermal keratinocytes. Reverse transcription PCR confirmed Gria4 transcript expression in epidermal mouse keratinocytes. In addition, expression of GRIA4 mRNA was confirmed in epidermal human keratinocytes by in situ hybridization. Immunohistochemical studies conducted in human skin biopsies from patients with atopic dermatitis and postherpetic neuralgia demonstrate that keratinocyte expression of GluA4 can be altered under pathological conditions. Moreover, a decrease of GluA4 expression was observed in organotypic cultures of human keratinocytes after direct application of algogenic agents.

Conclusion: We provide evidence that GluA4-containing AMPARs are expressed in epidermal keratinocytes, that human pruritic and painful dermatopathologies have alterations in the keratinocyte expression levels of GluA4-containing AMPAR, and that itch- and pain-producing substances can directly regulate their production in keratinocytes.

Skin Biopsy, the Allergists' Tool: How to Interpret a Report

Inflammatory dermatoses are frequently encountered by the allergist, and histologic evaluation achieved through skin biopsy can be of tremendous value clinically. There is no substitute for a thorough history and physical exam; however, the skin biopsy is a simple, in-office procedure with little risk of complication that can provide invaluable information when a diagnosis is uncertain. Histopathologically, many inflammatory eruptions can look similar or overlap, but information provided by the dermatopathologist can help the clinician render or refine the clinical diagnosis and guide management. This review will discuss descriptive elements contained in the pathology report to provide a framework that can be used by the allergist to comfortably and confidently diagnose inflammatory dermatologic conditions.

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.

Caspase-14-deficient mice are more prone to the development of parakeratosis

Caspase-14 is an important protease in the proper formation of a fully functional skin barrier. Newborn mice that are deficient in caspase-14 exhibit increased transepidermal water loss and are highly sensitive to UVB-induced photodamage. Decreased caspase-14 expression and incomplete caspase-14 processing in lesional psoriatic parakeratotic stratum corneum has been reported previously. In this study, we show that caspase-14-deficient skin frequently displays incompletely cornified cells in the transitional zone between the granular and the cornified layers, pointing to a delay in cornification. We also demonstrate that after challenge of epidermal permeability barrier function by repetitive acetone treatment, a higher incidence of large parakeratotic plaques was observed in caspase-14-deficient skin. Furthermore, caspase-14-deficient mice are more prone than control mice to the development of parakeratosis upon induction of psoriasis-like dermatitis by imiquimod treatment. These results show that lack of caspase-14 expression predisposes to the development of parakeratosis and that caspase-14 has an important role in keratinocyte terminal differentiation and the maintenance of normal stratum corneum, especially in conditions causing epidermal hyperproliferation.

2-Chloroethyl ethyl sulfide causes microvesication and inflammation-related histopathological changes in male hairless mouse skin

Sulfur mustard (HD) is a vesicating agent that has been used as a chemical warfare agent in a number of conflicts, posing a major threat in both military conflict and chemical terrorism situations. Currently, we lack effective therapies to rescue skin injuries by HD, in part, due to the lack of appropriate animal models, which are required for conducting laboratory studies to evaluate the therapeutic efficacy of promising agents that could potentially be translated in to real HD-caused skin injury. To address this challenge, the present study was designed to assess whether microvesication could be achieved in mouse skin by an HD analog 2-chloroethyl ethyl sulfide (CEES) exposure; notably, microvesication is a key component of HD skin injury in humans. We found that skin exposure of male SKH-1 hairless mice to CEES caused epidermal-dermal separation indicating microvesication. In other studies, CEES exposure also caused an increase in skin bi-fold thickness, wet/dry weight ratio, epidermal thickness, apoptotic cell death, cell proliferation, and infiltration of macrophages, mast cells and neutrophils in male SKH-1 hairless mouse skin. Taken together, these results establish CEES-induced microvesication and inflammation-related histopathological changes in mouse skin, providing a potentially relevant laboratory model for developing effective countermeasures against HD skin injury in humans.

Efficacy study of vesicular gel containing methotrexate and menthol combination on parakeratotic rat skin model

Methotrexate (MTX) is indicated in the symptomatic control of severe, recalcitrant, and disabling psoriasis. The oral or parenteral route of administration causes systemic toxicity. The topical route of delivery, though, reduces systemic toxicity and has limited applicability due to restricted permeability. Liposomal and niosomal MTX topical formulations have also been investigated with limited success to achieve drug localization in the skin. Menthol has been suggested in conditions of psoriasis, in addition to its skin-penetration-enhancing effect on drugs. The present work aimed at investigating the potential benefits of combining menthol with MTX in a vesicular gel base for not only improving the penetration and dermal availability of MTX, but also to render such a formulation more effective with greater patient acceptability. MTX liposomes were prepared by thin-film hydration, and the vesicles were characterized for drug-entrapment efficiency, size, and morphology. These liposomal vesicles were incorporated in a gel base, and this vesicular gel was evaluated for transdermal drug permeation and extent of drug accumulation in the skin, using a rat skin ex vivo model. Skin histology studies were carried out to investigate any structural changes caused by the permeation enhancers. Antipsoriatic efficacy of the formulations was tested in vivo, using the rat tail model. The results indicated that the vesicular gel containing menthol could cause maximum drug retention in the skin. The skin treated with menthol had a disrupted epidermis and microcavities. The in vivo studies also ascertained the effectiveness of the formulation in inducing a normal pattern of differentiation in the rat tail skin that initially showed parakeratosis, which is also characteristic of psoriatic epidermis. These results show the potential of vesicular gel containing MTX and menthol to improve penetration into the skin and cause drug retention in skin appendages.

Heterogeneity of fluorescence in psoriasis after application of 5-aminolaevulinic acid: an immunohistochemical study

BACKGROUND

Psoriasis has been shown to highly accumulate protoporphyrin IX (PpIX), but a variable distribution within plaques after fluorescence diagnosis is seen. It is unknown what causes this heterogeneity of fluorescence in psoriatic skin, despite adequate keratolytic treatment. Variations in fluorescence might explain the variable and the mostly partial clinical response of psoriasis seen after photodynamic therapy (PDT).

OBJECTIVES

This study examines morphological and immunohistochemical differences in inhomogeneous PpIX-induced fluorescence in stable plaque psoriasis.

MATERIALS AND METHODS

Fourteen patients with stable plaque psoriasis were included in this study. In each patient one psoriatic plaque was incubated with 20% 5-aminolaevulinic acid (ALA) ointment for 3 h after keratolytic treatment. Fluorescence diagnosis with ALA-induced porphyrins (FDAP) was performed and subsequently high- and low-fluorescent psoriatic skin samples were biopsied. Biopsies were investigated with respect to histological hyperkeratosis (thickness of stratum corneum), proliferation (Ki-67 antigen), keratinization (K10, filaggrin) and inflammation (CD3). Digital images acquired with FDAP were analysed using image analysis software.

RESULTS

Inhomogeneous fluorescence was seen in 12 of the 14 plaques. A significantly thicker stratum corneum was found in low-fluorescent psoriatic skin compared with highly fluorescent skin. Fluorescence intensity and thickness of the stratum corneum proved to be negatively correlated. The variable-fluorescent parts of the lesional psoriatic skin showed no differences in epidermal proliferation, keratinization or inflammation.

CONCLUSIONS

Heterogeneous ALA-induced fluorescence in psoriasis plaques related to inhomogeneous distribution of PpIX in the epidermis may result from differences in penetration of ALA and/or light within a plaque caused by differences in stratum corneum thickness. The variable clinical response seen after PDT in psoriasis could be explained by this. These findings are consistent with the general assumption that optimal desquamation prior to FDAP or PDT is required for the most favourable results.

Granular parakeratosis: Pathologic and clinical correlation of 18 cases of granular parakeratosis

BACKGROUND

Granular parakeratosis (originally termed axillary granular parakeratosis) is an idiopathic, benign, nondisabling cutaneous disease that manifests with intertriginous erythematous, brown or red, scaly or keratotic papules and plaques. It presents in all age groups and has no established clinical associations.

OBJECTIVES

We wanted to assess the following: (1) the incidence of granular parakeratosis in biopsy specimens; (2) the differential diagnosis submitted with specimens requisition of granular parakeratosis; and (3) variations in its histopathology.

METHODS

Between July 1, 1999 and December 31, 2003, 363,343 specimens were submitted to The Ackerman Institute of Dermatopathology in New York. A computer search was done of these specimen records and cases diagnosed with granular parakeratosis were reviewed. A thickened stratum corneum with retention of keratohyalin granules was considered diagnostic of granular parakeratosis.

RESULTS

Eighteen of 363,343 specimens (0.005%) were diagnosed with granular parakeratosis. The diagnosis was confirmed by re-review of specimens. All lesions were located in the axillae. All patients were adults; most were women. In only one instance was the correct clinical diagnosis of granular parakeratosis submitted with a biopsy requisition of it. Granular parakeratosis is rare, if its incidence among biopsy specimens is representative of its true prevalence. The failure to include granular parakeratosis on biopsy requisition forms of granular parakeratosis specimens indicates that dermatologists are not familiar with it. Variations of the histopathology of the 18 cases occurred but did not correlate with the clinical impressions included on biopsy requisition forms.