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Keratosis pilaris (KP) is a common, hyperkeratotic skin condition characterized by small, folliculocentric papules with variable perifollicular erythema. We provide an updated review on the pathogenesis, clinical manifestations, and management of this common, and often annoying, finding. KP represents a family of follicular disorders, of which KP simplex is by far the most common. Other variants and rare subtypes include keratosis pilaris rubra, erythromelanosis follicularis faciei et colli, and the spectrum of keratosis pilaris atrophicans. Inherited mutations of the FLG gene and ABCA12 gene have been implicated etiologically. KP may be associated with ichthyosis vulgaris and palmar hyperlinearity, but less likely atopic dermatitis. Some potential differential diagnoses for KP include lichen spinulosus, phrynoderma, ichthyosis vulgaris, and trichostasis spinulosa. General cutaneous measures such as hydrating skin, avoiding long baths or showers, and using mild soaps or cleansers should be recommended. Topical keratolytic agents are first-line therapy, followed by topical retinoids and corticosteroids. Recent options include a variety of lasers and microdermabrasion if the patient is refractory to topical therapy.

Background: Filaggrin is a protein integral to the structure and function of the epidermis. Filaggrin (FLG) loss-of-function (LOF) mutations are common and increase the risk of developing atopic dermatitis (AD) and ichthyosis vulgaris (IV). Epidemiologic data suggest a link between skin cancer and AD. We examined if FLG staining pattern can be used to characterize cutaneous squamous cell carcinomas (SCC), basal cell carcinomas (BCC), and reactive squamous epithelium., Methods: Tissue microarrays (TMAs) were created from 196 cases of formalin-fixed paraffin-embedded (FFPE) SCC and 144 BCC cases. TMAs and sections of reactive squamous epithelium were stained with optimized anti-FLG antibody and evaluated for FLG expression (normal, abnormal, or negative)., Results: FLG was absent in poorly differentiated (PD) compared to well-differentiated (WD) SCC (P < .0001) and moderately-differentiated (MD) (P = .0231) SCC, and in MD compared to WD SCC (P = .0099). Abnormal staining was significantly increased in PD compared to WD cases (P = .0039) and in MD compared to WD cases (P = .0006). Most BCC did not exhibit FLG expression (P < .05). Reactive squamous epithelium demonstrated normal, but exaggerated FLG expression., Conclusions: Our findings demonstrate the differences in FLG expression patterns in types of keratinocyte carcinomas and their mimickers., (© 2021 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Atopic dermatitis (AD) is characterized by dry and itchy skin evolving into disseminated skin lesions. AD is believed to result from a primary acquired or a genetically-induced epidermal barrier defect leading to immune hyper-responsiveness. Filaggrin (FLG) is a protein found in the cornified envelope of fully differentiated keratinocytes, referred to as corneocytes. Although FLG null mutations are strongly associated with AD, they are not sufficient to induce the disease. Moreover, most patients with ichthyosis vulgaris (IV), a monogenetic skin disease characterized by FLG homozygous, heterozygous, or compound heterozygous null mutations, display non-inflamed dry and scaly skin. Thus, all causes of epidermal barrier impairment in AD have not yet been identified, including those leading to the Th2-predominant inflammation observed in AD. Three dimensional organotypic cultures have emerged as valuable tools in skin research, replacing animal experimentation in many cases and precluding the need for repeated patient biopsies. Here, we review the results on IV and AD obtained with epidermal or skin equivalents and consider these findings in the context of human in vivo data. Further research utilizing complex models including immune cells and cutaneous innervation will enable finer dissection of the pathogenesis of AD and deepen our knowledge of epidermal biology.

Previous transcriptome analyses underscored the importance of immunological and skin barrier abnormalities in atopic dermatitis (AD). We sought to identify pathogenic pathways involved in AD by comparing the transcriptomes of AD patients stratified for filaggrin (FLG)-null mutations to those of both healthy donors and patients with ichthyosis vulgaris. We applied RNA sequencing to analyze the whole transcriptome of nonlesional skin. We found that 607 genes (476 up-regulated and 131 down-regulated by >2-fold) and 193 genes (172 up-regulated and 21 down-regulated by >2-fold) were differentially expressed when all AD or ichthyosis vulgaris patients were compared with healthy donors, respectively. Expression of genes involved in RNA/protein turnover and adenosine triphosphate synthesis, as well as genes involved in cell death, response to oxidative stress, DNA damage/repair, and autophagy, were significantly enriched in AD skin and, to a lesser extent, in ichthyosis vulgaris skin. FLG-null mutations appear to hardly interfere with current observations. Genes related to xenobiotic metabolism were up-regulated in AD skin only, as were genes related to arachidonic, linoleic, and α-linolenic acid metabolism. Thus, this work newly links AD pathogenesis to aberrant expression of genes related to xenobiotic metabolism., (Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Symmetrical acrokeratoderma seems to be a new disorder in China, and 138 cases have been reported in the Chinese literature., Objective: We sought to summarize the clinicopathologic features and immunophenotyping of inflammatory cells in 34 new cases., Methods: Clinical data of 34 patients were prospectively collected over 4 years. Histopathology and immunostaining of infiltrated cells were performed in 27 and 9 patients, respectively., Results: Brown to black hyperkeratotic patches were symmetrically distributed over the acral regions in 33 cases and on the scalp in 1 case, with a whitish change after water contact or sweating. The condition was aggravated in summer and alleviated in winter in 33 patients. History of ichthyosis vulgaris was seen in 23 cases. The typical histopathology included epidermal hyperkeratosis, acanthosis, and papillary dermal perivascular infiltrate of lymphohistiocytes. Number of CD3(+), CD4(+), and CD8(+) cells increased in lesional and perilesional skin compared with normal-appearing skin. The skin lesions developed slowly but were confined to the acral predilection sites after the mean follow-up of 25.4 ± 13.8 months., Limitations: The follow-up time was short., Conclusion: This disorder may represent a peculiar dermatosis that is frequently associated with ichthyosis vulgaris. No specific therapy is available for the disorder., (Copyright © 2013 American Academy of Dermatology, Inc. Published by Mosby, Inc. All rights reserved.)

Background: Atopic dermatitis (AD), Netherton syndrome (NS) and peeling skin syndrome type B (PSS) may show some clinical phenotypic overlap. Corneodesmosomes are crucial for maintaining stratum corneum integrity and the components' localization can be visualized by immunostaining tape-stripped corneocytes. In normal skin, they are detected at the cell periphery., Objective: To determine whether AD, NS, PSS and ichthyosis vulgaris (IV) have differences in the corneodesmosomal components' distribution and corneocytes surface areas., Methods: Corneocytes were tape-stripped from a control group (n=12) and a disease group (37 AD cases, 3 IV cases, 4 NS cases, and 3 PSS cases), and analyzed with immunofluorescent microscopy. The distribution patterns of corneodesmosomal components: desmoglein 1, corneodesmosin, and desmocollin 1 were classified into four types: peripheral, sparse diffuse, dense diffuse and partial diffuse. Corneocyte surface areas were also measured., Results: The corneodesmosome staining patterns were abnormal in the disease group. Other than in the 3 PSS cases, all three components showed similar patterns in each category. In lesional AD skin, the dense diffuse pattern was prominent. A high rate of the partial diffuse pattern, loss of linear cell-cell contacts, and irregular stripping manners were unique to NS. Only in PSS was corneodesmosin staining virtually absent. The corneocyte surface areas correlated significantly with the rate of combined sparse and dense diffuse patterns of desmoglein 1., Conclusion: This method may be used to assess abnormally differentiated corneocytes in AD and other diseases tested. In PSS samples, tape stripping analysis may serve as a non-invasive diagnostic test., (Copyright © 2013 Japanese Society for Investigative Dermatology. Published by Elsevier Ireland Ltd. All rights reserved.)

Loss-of-function mutations in human profilaggrin gene have been identified as the cause of ichthyosis vulgaris (IV), and as a major predisposition factor for atopic dermatitis (AD). Similarly, flaky tail (a/a ma ft/ma ft/J) mice were described as a model for IV, and shown to be predisposed to eczema. The aim of this study was to correlate the flaky tail mouse phenotype with human IV and AD, in order to dissect early molecular events leading to atopic dermatitis in mice and men, suffering from filaggrin deficiency. Thus, 5-days old flaky tail pups were analyzed histologically, expression of cytokines was measured in skin and signaling pathways were investigated by protein analysis. Human biopsies of IV and AD patients were analyzed histologically and by real time PCR assays. Our data show acanthosis and hyperproliferation in flaky tail epidermis, associated with increased IL1β and thymic stromal lymphopoietin (TSLP) expression, and Th2-polarization. Consequently, NFκB and Stat pathways were activated, and IL6 mRNA levels were increased. Further, quantitative analysis of late epidermal differentiation markers revealed increased Small proline-rich protein 2A (Sprr2a) synthesis. Th2-polarization and Sprr2a increase may result from high TSLP expression, as shown after analysis of 5-days old K14-TSLP tg mouse skin biopsies. Our findings in the flaky tail mouse correlate with data obtained from patient biopsies of AD, but not IV. We propose that proinflammatory cytokines are responsible for acanthosis in flaky tail epidermis, and together with the Th2-derived cytokines lead to morphological changes. Accordingly, the a/a ma ft/ma ft/J mouse model can be used as an appropriate model to study early AD onset associated with profilaggrin deficiency.

Loss-of-function mutations in the gene encoding filaggrin (FLG) can cause the semidominant keratinizing disorder ichthyosis vulgaris (OMIM 146700). To identify FLG mutations in three Chinese pedigrees with ichthyosis vulgaris, we sequenced the entire coding region of FLG in the proband of each pedigree. We found two novel FLG null mutations (c.477-478insA and c.6218-6219delAA) and a known mutation (c.3321delA). Both novel mutations were identified in the proband of pedigree 1; c.477-478insA was inherited from the proband's father, and the other was a de novo mutation. Neither of these two mutations was found in 200 unrelated controls. These findings extend the spectrum of functional FLG variants possibly causing ichthyosis vulgaris. Interestingly, the proband of pedigree 1 was compound heterozygous for these mutations, but had a mild phenotype, suggesting that an incomplete penetrance factor and perhaps other unknown factors may be involved in the pathogenesis of ichthyosis vulgaris., (© The Author(s). CED © 2012 British Association of Dermatologists.)

Background: Filaggrin gene (FLG) mutations have been identified as the cause of ichthyosis vulgaris (IV) and major predisposing factors for atopic dermatitis (AD). The relationship among AD, IV and FLG mutations has not been clarified yet. Mutations 3321delA and K4671X, two of the most common mutations in Chinese patients, were both statistically associated with AD in case-control studies., Materials and Methods: A group of 100 family trios (a total of 300 members with one affected AD proband and both parents) were recruited and screened for three filaggrin null mutations (3222del4, 3321delA and K4671X). The subjects' manifestations of AD and IV were assessed by two experienced dermatologists and recorded in detail. The relationship of common mutations to AD were assessed using both case-control and family-based tests of association. Filaggrin expression was measured in skin of 3 subjects with K4671X heterozygote and the normal control using quantitative real-time RT-PCR and immunohistochemistry., Results: Of 100 probands for AD, 22 were carriers for common FLG mutations and only 2 of them were from 40 none-IV family trios (5.00%), consistent with that of the healthy control group (3.99%, P>0.05). Significant statistical associations were revealed between AD and 3321delA (P<0.001, odds ratio 12.28, 95% confidence interval 3.35-44.98) as well as K4671X (P = 0.002, odds ratio 4.53, 95% confidence interval 1.77-11.60). The family-based approach revealed that 3321delA was over-transmitted to AD offspring from parents (T:U = 12∶1, P = 0.003) but failed to demonstrate transmission disequilibrium between K4671X and AD (T:U = 10∶8, P = 0.815). Moreover, compared to the normal control, filaggrin expression at both mRNA and protein levels in epidermis of subjects with K4671X(heter) was not reduced., Conclusions: AD patients from none-IV family trios have low probability of carrying FLG mutations. The present family samples confirmed the susceptibility of mutation 3321delA to AD in Han Chinese. K4671X was not a pathogenic mutation.

Background: Ichthyoses are genetic disorders of keratinization which are uncomfortable due to their conspicuous scaling, itching and cosmetic problems. Ichthyoses can lead to social discrimination and psychological problems. Ichthyosis vulgaris (IV) is the most common form of these geno-dermatoses. IV is a chronic disorder that often requires continuous therapy. Emollient and keratolytic products are the mainstay treatments of IV. It is important that efficient, safe and well tolerated therapies should be available. Direct comparative data regarding efficacy of different emollient products in IV patients are very few., Objective: The aim of the study was to investigate the keratolytic and moisturizing properties as well as the tolerance of a new urea topical formulation (Ureadin Rx10) when applied to hyperkeratotic and dry skin in patients with (IV) in comparison with a standard emollient cream., Methods: The study was conducted as a two-center, randomized, controlled, single-blind, intra-patient (right-vs.-left) trial design. A total of 30 patients with IV between 8 and 65 (mean age: 25 years) treated with a 10% urea-based lotion, Ureadin Rx 10 * *Ureadin RX 10 is a registered trade name of ISDIN, Spain. (URx), for 4 weeks or a glycerol-based emollient cream, Dexeryl † †Dexeryl is a registered trade name of Pierre Fabre Dermatologie. (DC), in a right-vs.-left study design. Primary outcome was a 5-point SRRC Index score (evaluating scaling roughness, redness and cracks) evaluated at baseline and after 2 and 4 weeks of treatment. As secondary endpoints patients evaluated also the global efficacy (GE) and global tolerability (GT) scores with the help of a 10 cm visual analogue scale (0 = no efficacy at all/very bad tolerability; 10: excellent efficacy/excellent tolerability)., Results: At baseline the mean (SD) SRRC score was 9.5 (1.9) in the URx treated sites and 9.5 (1.9) in the DC treated sites. A total of 27 patients (90%) concluded the study period. Three patients were withdrawn prematurely because of itching and burning sensation after DC application (1 patient) or URx application (2 patients). At week 4, in comparison with baseline values, both treatments were shown to be clinically effective: SRRC significantly (p = 0.0001) decreased to 3.3 (1.8) after URx (a 65% relative reduction) and to 5.7 (2.5) after DC (a 40% relative reduction). SRRC was significantly lower in URx treated regions in comparison with DC both after 2 and 4 weeks of treatment (p = 0.0005). Mean GE score in areas treated with URx was significantly (p = 0.0001) higher than in the areas treated with the DC (8.9 vs.7.3). Both treatments were in general well tolerated. GT score was 8.1 (range 10 to 3) with URx and 8.4 (range 10 to 3) with DC application (p = ns). The two main limitations of this trial are the study design (single blind), and the small sample size which is not adequate for an evaluation of safety., Conclusion: Ureadin Rx 10 lotion has shown a greater efficacy on ichthyosis vulgaris in term of reduction of scaling, roughness, redness and cracking in comparison with a glycerol-based emollient cream. Tolerability of the two topical treatments was comparable. Further studies with larger sample sizes are needed for the evaluation of safety and tolerability of urea 10% lotion in this clinical setting.

Although it is widely accepted that filaggrin (FLG) deficiency contributes to an abnormal barrier function in ichthyosis vulgaris and atopic dermatitis, the pathomechanism of how FLG deficiency provokes a barrier abnormality in humans is unknown. We report here that the presence of FLG mutations in Caucasians predicts dose-dependent alterations in epidermal permeability barrier function. Although FLG is an intracellular protein, the barrier abnormality occurred solely via a paracellular route in affected stratum corneum. Abnormal barrier function correlated with alterations in keratin filament organization (perinuclear retraction), impaired loading of lamellar body contents, followed by nonuniform extracellular distribution of secreted organelle contents, and abnormalities in lamellar bilayer architecture. In addition, we observed reductions in corneodesmosome density and tight junction protein expression. Thus, FLG deficiency provokes alterations in keratinocyte architecture that influence epidermal functions localizing to the extracellular matrix. These results clarify how FLG mutations impair epidermal permeability barrier function., (Copyright © 2011 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.)

Dermoscopy is a noninvasive technique to assess skin architecture. A pilot study was conducted using polarized dermoscopy as a tool to monitor the pediatric skin barrier. Ten pediatric patients (age range, 1-14 years) with mild to moderate atopic dermatitis (AD), ichthyosis vulgaris (IV), and/or keratosis pilaris (KP) participated in a 4-week clinical trial. After a week of emollient usage alone, a mid-potency topical corticosteroid cream was added twice daily if necessary to treat erythema, dermatitis, or pruritus. The participants were assessed at weeks 0, 1, and 4 using the eczema area and severity index (EASI) for atopic dermatitis, investigator global assessment for atopic dermatitis, children dermatology life quality index (CDLQI), and clinical and dermoscopic photography. Dermoscopic appearance demonstrated dermal vascular ectasia in AD and KP, hyperkeratosis and prominence of the interkeratinocyte space in AD and IV and widening of the follicular orifice in KP. Improvements in these dermoscopic abnormalities were noted after emollient usage, mirroring improvements in clinical appearance, EASI, and CDLQI. Dermoscopy is a promising tool to assess localized improvement in skin architecture in pediatric dermatoses. Further studies and development of scoring systems will be needed to apply this technology to clinical practice.

Ichthyosis vulgaris is a common genetic skin disorder with an estimated prevalence of 1:250 caused by mutations in the gene encoding filaggrin. This disorder manifests itself within the first year of life and is clinically characterized by dry, scaly skin, keratosis pilaris, palmar hyperlinearity and atopic manifestations. Patients with a severe phenotype are homozygous or compound heterozygous for the mutations, whereas heterozygous patients show mild disease, suggesting semidominant inheritance with incomplete penetrance. We present a patient with classic severe ichthyosis vulgaris, atopic eczema and two loss-of-function mutations.

Background: Several common genetic and environmental disease mechanisms are important for the pathophysiology behind atopic dermatitis (AD). Filaggrin (FLG) loss-of-function is of great significance for barrier impairment in AD and ichthyosis vulgaris (IV), which is commonly associated with AD. The molecular background is, however, complex and various clusters of genes are altered, including inflammatory and epidermal-differentiation genes., Objective: The objective was to study whether the functional and molecular alterations in AD and IV skin depend directly on FLG loss-of-function, and whether FLG genotype determines the type of downstream molecular pathway affected., Methods and Findings: Patients with AD/IV (n = 43) and controls (n = 15) were recruited from two Swedish outpatient clinics and a Swedish AD family material with known FLG genotype. They were clinically examined and their medical history recorded using a standardized questionnaire. Blood samples and punch biopsies were taken and trans-epidermal water loss (TEWL) and skin pH was assessed with standard techniques. In addition to FLG genotyping, the STS gene was analyzed to exclude X-linked recessive ichthyosis (XLI). Microarrays and quantitative real-time PCR were used to compare differences in gene expression depending on FLG genotype. Several different signalling pathways were altered depending on FLG genotype in patients suffering from AD or AD/IV. Disease severity, TEWL and pH follow FLG deficiency in the skin; and the number of altered genes and pathways are correlated to FLG mRNA expression., Conclusions: We emphasize further the role of FLG in skin-barrier integrity and the complex compensatory activation of signalling pathways. This involves inflammation, epidermal differentiation, lipid metabolism, cell signalling and adhesion in response to FLG-dependent skin-barrier dysfunction.

The skin is the outer layer of protection against the environment. The development and formation of the skin is regulated by several genetic cascades including the bone morphogenetic protein (BMP) signaling pathway, which has been suggested to play an important role during embryonic organ development. Several skin defects and diseases are caused by genetic mutations or disorders. Ichthyosis is a common genetic skin disorder characterized by dry scaly skin. Loss-of-function mutations in the filaggrin (FLG) gene have been identified as the cause of the ichthyosis vulgaris (IV) phenotype; however, the direct regulation of filaggrin expression in vivo is unknown. We present evidence that BMP signaling regulates filaggrin expression in the epidermis. Mice expressing a constitutively active form of BMP-receptor-IB in the developing epidermis exhibit a phenotype resembling IV in humans, including dry flaky skin, compact hyperkeratosis, and an attenuated granular layer associated with a significantly downregulated expression of filaggrin. Regulation of filaggrin expression by BMP signaling has been further confirmed by the application of exogenous BMP2 in skin explants and by a transgenic model overexpressing Noggin in the epidermis. Our results demonstrate that aberrant BMP signaling in the epidermis causes overproliferation and hyperkeratinization, leading to an IV-like skin disease.

Objective: To target and amplify a 1.5 kb FLG gene fragment known to carry R501X mutation responsible for causing ichthyosis vulgaris., Study Design: A case series., Place and Duration of Study: Centre for Molecular Genetics, University of Karachi and Dermatology Department, Jinnah Postgraduate Medical Centre (JPMC), Karachi, from October 2007 to December 2008., Methodology: Clinically examined seven ichthyosis vulgaris families were included in this study. The 1.5 kb FLG gene fragment was located in the genomic DNA of both the affected (patients) and unaffected (normal, controls) members of the families by PCR amplification using known primers FilF3 and RPTIP6., Results: Amplification of 1.5 kb FLG gene fragment was successful in four families while one family showed amplification of the gene fragment in 3 members (one affected and two normal). Two families showed no amplification., Conclusion: The results obtained during this study suggested the possibility of the R501X mutation as being one of the major causes of ichthyosis vulgaris in Pakistan. In addition, the study also revealed the possibility of the presence of novel FLG gene mutations in our population.

Pachyonychia congenita (PC), a rare autosomal-dominant keratin disorder caused by mutations in keratin genes KRT6A/B, KRT16 or KRT17, is characterized by painful plantar keratoderma and hypertrophic nail dystrophy. Loss-of-function mutations in the filaggrin (FLG) gene underlie the most prevalent skin disorder of cornification, ichthyosis vulgaris (IV), which presents with generalized scaling and is also associated with atopic dermatitis. Recently, FLG mutations have been reported to increase phenotype severity of X-linked ichthyosis and alopecia areata. We report a parent-child trio in which the mother and the son have PC and the father has IV. Both the mother and the son are carriers for the KRT16 mutation p.Leu132Pro. The son, who is much more severely affected than his mother, in addition carries the heterozygous FLG mutation p.R2447X, which was inherited from the father. This observation suggests that coinheritance of mutations in KRT16 and FLG may aggravate the PC phenotype and that FLG could serve as a genetic modifier in PC.

Recently, loss-of-function mutations in FLG, the human gene encoding profilaggrin and filaggrin, have been identified as the cause of the common skin condition ichthyosis vulgaris (which is characterised by dry, scaly skin). These mutations, which are carried by up to 10% of people, also represent a strong genetic predisposing factor for atopic eczema, asthma and allergies. Profilaggrin is the major component of the keratohyalin granules within epidermal granular cells. During epidermal terminal differentiation, the approximately 400 kDa profilaggrin polyprotein is dephosphorylated and rapidly cleaved by serine proteases to form monomeric filaggrin (37 kDa), which binds to and condenses the keratin cytoskeleton and thereby contributes to the cell compaction process that is required for squame biogenesis. Within the squames, filaggrin is citrullinated, which promotes its unfolding and further degradation into hygroscopic amino acids, which constitute one element of natural moisturising factor. Loss of profilaggrin or filaggrin leads to a poorly formed stratum corneum (ichthyosis), which is also prone to water loss (xerosis). Recent human genetic studies strongly suggest that perturbation of skin barrier function as a result of reduction or complete loss of filaggrin expression leads to enhanced percutaneous transfer of allergens. Filaggrin is therefore in the frontline of defence, and protects the body from the entry of foreign environmental substances that can otherwise trigger aberrant immune responses.

Subcutaneous calcification following radiotherapy is a very rare late complication. Here we report a case of radiotherapy for Hodgkin's disease in a patient with ichthyosis. Our review of the literature revealed that subcutaneous calcifications occurred in previously normal skin following irradiation. In our case the calcification developed in abnormal skin after telecobalt radiotherapy for mediastinal Hodgkin's disease. Ichthyosis is a systemic cutaneous disease and may increase the risk of late radiation complications.

Purpose of Review: To provide a comprehensive summary of recent genetic advances as they relate to the pathogenesis of atopic dermatitis., Recent Findings: Atopic dermatitis is a common inflammatory skin disease with a complex cause, resulting from an elaborate interplay between environmental, immunological and genetic factors. The disease is often the prelude to an atopic diathesis that includes asthma and other allergic diseases. The identification of mutations in the barrier protein filaggrin as conferring major susceptibility to atopic dermatitis and atopic dermatitis related asthma has reconfigured our understanding of disease mechanisms and highlights the importance of epidermal barrier disruption as a primary event in the disease., Summary: In this review we highlight recent advances in our understanding of how filaggrin might influence the environmental-immune interface, impacting disease penetrance, severity and trajectory, and the implications for both research and therapeutics in this field. Focusing on the downstream biological consequences of altered filaggrin expression and the sequence of immunological and environmental triggers that ensue will provide the rationale for targeted therapeutics capable of restoring or preventing disruption of barrier function.

We report a 17-year-old girl who presented with linear and whorled melanosis following Blaschko lines mainly on her trunk. Ichthyosiform lesions and linear scaling erythemas were observed respectively on her lower limbs and the dorsa of her hands, left knee, ankle and foot. No abnormality was found in systemic examination and blood tests. A biopsy specimen of pigmentation of her back showed there was increased pigmentation within the basal keratinocytes, with focal incontinentia pigmenti. Notable lymphangiectasis could also be seen in the mid part of dermis, which had never previously been described. The biopsy of scaling erythemas of her hand showed dominant hyperkeratosis with focal parakeratosis, acanthosis and papillomatous hyperplasia in the epidermis. The diagnosis of linear and whorled nevoid hypermelanosis (LWNH) complicated with inflammatory linear verrucous epidermal nevus and ichthyosis vulgaris was made in accordance with clinical and pathological manifestations. LWNH ought to be differentiated from incontinentia pigmenti and hypomelanosis of Ito.

Ichthyosis vulgaris (IV) is the most common hereditary disorder of cornification in humans, characterized by generalized fine scaling of the skin, palmar hyperlinearity with or without keratosis pilaris and atopy. Recently, the molecular basis of IV was ascribed to loss-of-function mutations in the gene encoding filaggrin (FLG), namely p.R501X and c.2282del4. Homozygotes and compound heterozygotes were severely affected whereas heterozygotes showed mild disease or were asymptomatic, suggesting semidominant inheritance with incomplete penetrance in heterozygotes. We report the presence of FLG mutations in 15 out of 21 IV patients with a marked generalized scaling phenotype, including eight affected members of a four-generation family. In this group of patients not only homozygous and compound heterozygous, but also heterozygous patients for p.R501X and c.2282del4 display a pronounced phenotype, whereas in none of six individuals these two mutations were detectable despite decreased filaggrin expression on immunohistochemistry in two patients, indicating that other mutations in FLG and/or in other genes remain to be identified. In contrast, two additional p.R501X heterozygotes from the extended family are asymptomatic. In a control population from west-Austria a combined p.R501X and c.2282del4 carrier frequency of 6/110 (5.45%) was observed. We confirm that these FLG variants are common, but our results point to the existence of additional modifiers.

Ichthyosis vulgaris (IV), characterized by mild scaling on limbs and lower abdomen, has an incidence of 1 in 250. Smith, McLean, and colleagues demonstrate that common mutations in filaggrin underlie IV. Filaggrin aggregates keratin intermediate filaments and is cross-linked into the cornified envelope to form the epidermal barrier. These findings reinforce the importance of the epidermal barrier in pathogenesis of skin diseases.

The clinical, radiologic, histopathologic, and genetic features of a sclerosing bone dysplasia found in three members of a family are described. The bone disorder affected all metaphyseal-diaphyseal regions of all long bones, the skull, and three metacarpals. All affected members also had ichthyosis vulgaris and premature ovarian failure. These features have not been reported before, indicating a new syndrome.

Ichthyosis vulgaris (IV) is a mild to severe scaling disorder of uncertain etiology estimated to affect as many as 1 : 250 in the population. Family studies have shown that in many cases IV follows an autosomal dominant inheritance pattern, but gene mapping studies have not been reported. To investigate the genetic basis for inherited IV, we have performed gene linkage studies in two multigenerational families where affected individuals have clinical features of IV but distinct histological features. The epidermis in this disorder characteristically displays non-specific orthohyperkeratosis. Notably, a subset of IV patients with a reduced or absent granular epidermal layer (AGL) have been reported, and decreased filaggrin levels have been described in others. The prominent role of profilaggrin in human keratohyalin suggests that defects in the gene for profilaggrin (FLG), its processing of profillagrin to filaggrin, or a gene involved in profilaggrin regulation may underlie or modify the pathology in IV. Family 1 had seven individuals with IV, severe heat intolerance and epidermis with 1-3 granular layers (consistent with normal epidermal histology). Ichthyosis vulgaris in this family did not segregate with FLG or other genes in the epidermal differentiation complex. In contrast, five of the six IV patients in Family 2, all siblings, had epidermis with no granular layer. Significant evidence was obtained for linkage of IV with the associated AGL phenotype to the epidermal differentiation complex (which includes FLG) assuming either a recessive (max Lod 3.4) or dominant (max Lod 3.6) inheritance model. Sequence analysis of FLG did not reveal a mutation in the amino or carboxyl terminal portions of the coding sequence adjacent to filaggrin repeats. The AGL may represent an endophenotype for IV, and the presence of a modifier of IV pathology at this locus is discussed.

To explore the expression and gain more information on the function of transglutaminase 5 enzyme in normal and defective human epidermis, we generated a rat antihuman transglutaminase 5 antiserum elicited against a purified active recombinant protein expressed in the baculovirus system. By use of Western blotting and immunofluorescence methods, the immunospecificity of the antibodies for transglutaminase 5 was tested; no crossreactivity with other transglutaminases (types 1, 2, and 3) was observed, thus allowing histochemistry studies. By indirect immunofluorescence analysis the antibodies decorated the upper layers of normal human epidermis, with consistent staining in the spinous and granular layers. We evaluated transglutaminase 5 expression in comparison with proliferating (keratin 14) and differentiating (transglutaminase 3) markers in different diseases, such as psoriasis, ichthyosis vulgaris, lamellar ichthyosis, and Darier's disease. We observed that transglutaminase 5 contributes, as a secondary effect, to the hyperkeratotic phenotype in ichthyosis (both vulgaris and lamellar) and in psoriasis. In Darier's disease, transglutaminase 5 expression, as well as transglutaminase 3, is completely missregulated, being overexpressed or totally absent in different areas of the same lesion.

The clinical diagnosis of ichthyosis vulgaris (IV) can be difficult. Abnormalities in the granular layer and the ultrastructure of keratohyalin granules (KHG) suggest that morphology may be helpful. To clarify morphologic findings in IV, 41 clinically affected individuals and 21 unaffected family members or age- and sex-matched controls were studied by light microscopy. In these, the granular layer was totally absent in approximately 50% of affected individuals, while present in all controls. Forty-seven individuals in the light microscopy group were also studied by electron microscopy. Keratohyalin granules were absent in all affected individuals lacking the granular layer by light microscopy. Clinical severity usually correlated with the lack of a granular layer and KHG. Absence of the granular layer was consistent in different anatomic sites and in serial biopsies taken over a 1-3-year period. In a subset of clinically affected, unrelated subjects with moderate to severe involvement, four out of 11 (36%) had similar findings. Keratinocytes cultured from affected individuals with no KHG expressed virtually no detectable profilaggrin protein in vitro. The data suggest that a subset of individuals with moderate to severe IV have a consistently absent granular layer and KHG. Absence of the granular layer and lack of KHG correlated almost perfectly; thus light microscopy offers a convenient means of identifying this subtype of IV. However, both morphologic types of IV were observed within single families. Therefore, the relationship between granular layer abnormalities and IV is complex and requires the study of more affected families. One interpretation of the data is that IV is a multigenic disorder in which one of the genes alters profilaggrin expression. We propose this clinical and histologic phenotype as useful for identifying the gene(s) involved and also for determining whether it represents a modifier or a major locus of the disorder.

Diabetes has not been linked to acquired ichthyosis or ichthyosis vulgaris. We report a newly diagnosed diabetic 14-year-old girl with bilateral tibial and sacral ichthyosiform plaques and a hemoglobin A1c of 20.1%. The patient had no personal or family history of atopy or ichthyosis and lacked keratosis pilaris or hyperlinear palms. A biopsy specimen of an ichthyosiform plaque showed compact lamellar orthohyperkeratosis and hypogranulosis, histopathology consistent with either ichthyosis vulgaris or acquired ichthyosis. We speculate that our patient's new-onset diabetes induced acquired ichthyosis.

Background: Topical tacalcitol (1alpha,24-dihydroxyvitamin D3) has been demonstrated to produce beneficial clinical effects on epidermo-hyperproliferative disorders such as psoriasis and pityriasis rubra pilaris. However, the efficacy of the agent has not been elucidated in retentive hyperkeratotic disorders., Objective: The object of the study was to assess the clinical efficacy of topical tacalcitol against ichthyoses with retentive hyperkeratosis; X-linked ichthyosis (XLI), ichthyosis vulgaris (IV), and acquired ichthyosis (AI)., Methods: Tacalcitol was topically applied on 9 patients with the retention ichthyoses, using a single-blinded, bilaterally paired approach with right-left comparison of tacalcitol and the base., Results: Clinical improvement obtained by topical tacalcitol exclusively was not superior to that of the vehicle alone in any of the ichthyotic patients., Conclusion: Topical tacalcitol therapy was ineffective against ichthyoses without epidermal hyperproliferation., (Copyright 2001 S. Karger AG, Basel.)

A number of ichthyosis syndromes may have retinal abnormalities such as the retinitis pigmentosa-like diffuse rod-cone dystrophy in Refsum's syndrome and the maculopathy in Sjögren-Larsson syndrome. We present two sisters who have an unusual, almost identical, bilaterally symmetric central retinal dystrophy associated with ichthyosis vulgaris in the absence of other systemic disorders. We believe that this dystrophy has not been previously described in patients with any of the known varieties of ichthyosis.

Keratitis-ichthyosis-deafness (KID) syndrome is a congenital ectodermal disorder causing erythrokeratoderma, vascularizing keratitis, and neurosensory deafness. Ichthyosis hystrix is a rare cutaneous disease characterized by well-demarcated, spiky, verrucous, linear plaques that is believed to be a clinical and pathologic chimera of two autosomal dominant diseases: epidermal nevus and epidermolytic hyperkeratosis. We present a patient with the classic triad of KID syndrome with clinical and histologic features of ichthyosis hystrix. This case demonstrates that KID syndrome comprises a spectrum of ectodermal disorders which may include diseases such as hystrix ichthyosis and deafness (HID) syndrome.

Two patients with keratosis punctata of the palmar creases are described. The association with ichthyosis vulgaris and other disorders of keratinization is discussed. In both cases, histopathology revealed a close relation between the keratotic plug and the sweat glands. The role of genetic factors and manual activity in the pathogenesis is discussed. Treatment with oral etretinate resulted in a good improvement in the first patient, but prolonged low-dose maintenance therapy was required to prevent recurrence.

Ichthyosis vulgaris (IV) is an inherited scaling skin disorder in which expression of profilaggrin is reduced. Previous studies have indicated that the reduction is caused by defective post-transcriptional control of gene expression. Here we present evidence that profilaggrin mRNA in keratinocytes cultured from subjects with IV is intrinsically unstable and has a shorter half-life compared with that in normal cells. When IV-affected keratinocytes were treated with the protein synthesis inhibitor cycloheximide, the steady-state level of profilaggrin mRNA was increased due to stabilization of the transcript. In addition, the number of filaggrin repeats within the profilaggrin gene was studied. The number of filaggrin repeats (10-12) in individuals with IV did not differ from that of unaffected subjects. Expression of the gene was bi-allelic and coequal in both control and affected individuals. Our results suggest a model in which a labile ribonuclease and a stabilizing factor may modulate the profilaggrin mRNA steady-state level in normal cells, whereas the stabilizing factor may be absent or functionally inactive in IV-affected keratinocytes.

To elucidate the pathogenesis of impaired barrier function and the influence of surfactant on the stratum corneum in hyperkeratosis, we investigated morphological alterations of the corneocytes with soap solution. Groups of five patients each with psoriasis vulgaris (PV), ichthyosis vulgaris (IV), atopic dermatitis (AD), and normal controls were examined. Four samples of the horny layer were obtained from the same site by cyanoacrylate adhesive biopsy. The first sample was used for the superficial layer, and the fourth, for the basal horny layers. Each sample was agitated in 1% stirred soap solution at 60 degrees C. The number and size of isolated corneocytes and the morphologic changes were investigated. The release of corneocytes was greater and the swelling and morphological changes of corneocytes exposed to soap solutions were less in PV and AD than in IV or in healthy subjects. In IV, the release was markedly less than in controls. The release and swelling were greater in the superficial than in the basal horny layers. It was concluded that the cohesiveness of corneocytes was probably less in PV and AD and greater in IV than in normals. It was also suggested that the cohesion of corneocytes from the superficial horny layer was less than that from the deep layer. The permeability of the cornified envelope in PV and AD patients was less than in IV or healthy subjects. It was confirmed that highly potent soaps induce loss of many corneocytes and reduce the barrier function of the stratum corneum.

The clinical course of an ozaena in a patient with an autosomal dominant ichthyosis vulgaris was complicated by the skin disease related atopic disposition with allergic rhinitis. Electron microscopic studies of the pathologically keratinized mucosa of the nasopharynx revealed a similar defect of the mucosal keratohyalin caused by the absence of the protein filaggrin.

Standardized stereological methods were performed on biopsies from three subjects with normal skin and from three patients with autosomal dominant and three with autosomal recessive sex-linked ichthyosis to determine the relative numbers and dimensions of desmosomes. The results showed an increase in the persistence of desmosomes in the stratum corneum in both ichthyotic groups. This suggests a pathogenetic role for desmosomes in the abnormal desquamation of the two types of ichthyosis vulgaris.

Recent biochemical and morphological investigations have provided evidence for a heterogeneous composition of keratohyalin in human skin. A major component is filaggrin. In interfollicular epidermis the heterogeneity of keratohyalin is not directly visible, whereas in normal ridged skin bicomponent keratohyalin is revealed by electron microscopy. Skin biopsies of ridged and non-ridged skin of normal individuals and patients with autosomal dominant ichthyosis vulgaris (ADI)--characterized by defective keratohyalin synthesis and lack of filaggrin--were investigated by routine transmission electron microscopy and immunogold postembedding techniques using a commercial monoclonal anti-filaggrin antibody. In normal interfollicular epidermis filaggrin labelling was demonstrated on keratohyalin granules and in the lowermost cornified cells, whereas in ADI patients crumbly keratohyalin granules were present that did not show specific labelling for filaggrin. In normal ridged skin only the major (more electron-dense) component reacted with anti-filaggrin, whereas the attached (less electron-dense) component did not react. Ridged skin of ADI patients contained globular keratohyalin that did not react with anti-filaggrin, thus corresponding to the attached keratohyalin component in normal ridged skin. Our results provide a visible counterpart to the recent biochemical investigations of keratohyalin protein heterogeneity and contribute to the understanding of terminal differentiation in human skin and of the defective keratohyalin synthesis in ADI.