Filaggrin loss-of-function mutation R501X and 2282del4 carrier status is associated with fissured skin on the hands: results from a cross-sectional population study

Filaggrin mutations in relation to skin barrier and atopic dermatitis in early infancy

BACKGROUND

Loss-of-function mutations in the skin barrier gene filaggrin (FLG) increase the risk of atopic dermatitis (AD), but their role in skin barrier function, dry skin and eczema in infancy is unclear.

OBJECTIVES

To determine the role of FLG mutations for impaired skin barrier function, dry skin, eczema and AD at three months of age and through infancy.

METHODS

FLG mutations were analyzed in 1836 infants in the Scandinavian population-based PreventADALL study. Transepidermal water loss (TEWL), dry skin, eczema and AD were assessed at three, six and 12 months of age.

RESULTS

Filaggrin mutations were observed in 166 (9%) infants. At three months, carrying FLG mutations was not associated with impaired skin barrier function (TEWL > 11.3 g/m² /h) or dry skin, but with eczema (OR(95%CI): 2.76 (1.81, 4.23), p < 0.001). At six months, mutation carriers had significantly higher TEWL than non-mutation carriers (mean (95%CI) 9.68 (8.69, 10.68) vs. 8.24 (7.97, 8.15), p < 0.01) and at three and six months an increased risk of dry skin on truncus (OR: 1.87 (1.25, 2.80), p = 0.002; 2.44 (1.51, 3.95), p < 0.001) or extensor limb surfaces (1.52 (1.04, 2.22), p = 0.028; 1.74 (1.17, 2.57), p = 0.005). FLG mutations were associated with eczema and AD in infancy.

CONCLUSION

Filaggrin mutations were not associated with impaired skin barrier function or dry skin in general at three months of age, but increased the risk for eczema, as well as for dry skin on truncus and extensors at three and six months.

Diagnosis and treatment of xerosis cutis - a position paper

BACKGROUND AND RATIONALE

Xerosis cutis (also referred to as xeroderma, dry skin, asteatosis) affects more than 10 million individuals in Germany. It is among the most common dermatological diagnoses and a cardinal symptom of many dermatological, internal and neurological diseases. Even though it has been established that basic skin care plays a significant role in the management of patients with xerosis cutis, there are as yet no evidence-based algorithms for diagnosis and treatment.

OBJECTIVE

The present position paper provides physicians across all specialties with a practical, symptom-based approach to the prevention, diagnosis and treatment of xerosis cutis.

METHODS

Within a structured decision-making process, a panel of experienced dermatologists first defined questions relevant to everyday clinical practice, which were then addressed by a systematic review of the literature. Based on the evidence available as well as expert consensus, diagnostic and treatment algorithms were subsequently developed and agreed upon.

RESULTS

Xerosis cutis is generally diagnosed on clinical grounds. Possible trigger factors must be avoided, and comorbidities should be adequately and specifically treated. Suitable skin care products should be chosen with a view to improving skin hydration and restoring its barrier function. They should therefore contain both rehydrating and lipid-replenishing components. The "drier" the skin appears, the greater the lipid content should be (preferably using water-in-oil formulations). The choice of ingredients is based on a patient's individual symptoms, such as scaling (e.g., urea), fissures/rhagades (e.g., urea or dexpanthenol), erythema (e.g., licochalcone A) and pruritus (e.g., polidocanol). Other factors to be considered include the site affected and patient age. Ingredients or rather combinations thereof for which there is good clinical evidence should be preferentially used. The best evidence by far is available for urea, whose efficacy in the treatment of xerosis is further enhanced by combining it with other natural moisturizing components and ceramides. The "xerosimeter" is a tool developed in an effort to facilitate patient management and for training purposes. It not only includes practical tools for diagnosis and follow-up but also a classification of ingredients and a structured treatment algorithm.

CONCLUSION

The structured symptom- and evidence-based approach proposed herein contains a road map for diagnosis and treatment of xerosis cutis. It aims to raise awareness in terms of prevention and early treatment of this condition and may thus improve quality of life and prevent potential sequelae.

Identification of differentially expressed microRNAs in the skin of experimentally sensitized naturally affected atopic beagles by next-generation sequencing

Canine atopic dermatitis (AD) is a very common inflammatory skin disease, but limited data are available on the genetic characterization (somatic mutations, microarrays, and genome-wide association study (GWAS)) of skin lesions in affected dogs. microRNAs are good biomarkers in inflammatory and neoplastic diseases in people. The aim of this study was to evaluate microRNA expression in the skin of atopic beagles, before and after exposure to Dermatophagoides farinae. Four atopic and four unrelated age-matched healthy beagle dogs were enrolled. Total RNA was extracted from flash-frozen skin biopsies of healthy and atopic dogs. For the atopic dogs, skin biopsies were taken from non-lesional (day 0) and lesional skin (day 28 of weekly environmental challenge with Dermatophagoides farinae). Small RNA libraries were constructed and sequenced. The microRNA sequences were aligned to CanFam3.1 genome. Differential expressed microRNAs were selected on the basis of fold-change and statistical significance (fold-change ≥ 1.5 and p ≤ 0.05 as thresholds. A total of 277 microRNAs were sequenced. One hundred and twenty-one differentially regulated microRNAs were identified between non-lesional and healthy skin. Among these, two were increased amount and 119 were decreased amount. A total of 45 differentially regulated microRNAs between lesional and healthy skin were identified, 44 were decreased amount and one was increased amount. Finally, only two increased amount microRNAs were present in lesional skin when compared with that of non-lesional skin. This is the first study in which dysregulation of microRNAs has been associated with lesional and non-lesional canine AD. Larger studies are needed to understand the role of microRNA in canine AD.

Impact of Heavy Metals on Host Cells: Special Focus on Nickel-Mediated Pathologies and Novel Interventional Approaches

BACKGROUND

Heavy metals [arsenic, aluminium, cadmium, chromium, cobalt, lead, nickel (Ni), palladium and titanium] are environmental contaminants able to impact with host human cells, thus, leading to severe damage.

OBJECTIVE

In this review, the detrimental effects of several heavy metals on human organs will be discussed and special emphasis will be placed on Ni. In particular, Ni is able to interact with Toll-like receptor-4 on immune and non-immune cells, thus, triggering the cascade of pro-inflammatory cytokines. Then, inflammatory and allergic reactions mediated by Ni will be illustrated within different organs, even including the central nervous system, airways and the gastrointestinal system.

DISCUSSION

Different therapeutic strategies have been adopted to mitigate Ni-induced inflammatoryallergic reactions. In this context, the ability of polyphenols to counteract the inflammatory pathway induced by Ni on peripheral blood leukocytes from Ni-sensitized patients will be outlined. In particular, polyphenols are able to decrease serum levels of interleukin (IL)-17, while increasing levels of IL- 10. These data suggest that the equilibrium between T regulatory cells and T helper 17 cells is recovered with IL-10 acting as an anti-inflammatory cytokine. In the same context, polyphenols reduced elevated serum levels of nitric oxide, thus, expressing their anti-oxidant potential. Finally, the carcinogenic potential of heavy metals, even including Ni, will be highlighted.

CONCLUSION

Heavy metals, particularly Ni, are spread in the environment. Nutritional approaches seem to represent a novel option in the treatment of Ni-induced damage and, among them, polyphenols should be taken into consideration for their anti-oxidant and anti-inflammatory activities.

Filaggrin gene mutations and the distribution of filaggrin in oral mucosa of patients with oral lichen planus and healthy controls

BACKGROUND

Lichen planus (LP) is a chronic inflammatory disease of unknown aetiology affecting the skin and oral mucosa. Oral lichenoid lesions (OLLs), like oral contact reactions, may resemble oral lichen planus (OLP) both clinically and histopathologically. As OLP and OLL are hyperkeratotic diseases and filaggrin is essential to keratinization, the distribution of filaggrin may be altered in these lesions.

OBJECTIVES

To investigate whether patients with OLP/OLL have (i) altered distribution of filaggrin in the oral mucosa; (ii) a higher incidence of mutations in the filaggrin gene (FLG); (iii) active dermatoses, apart from cutaneous LP, than healthy controls; and (iv) patients with OLP/OLL and a defect in the FLG have more widespread oral lesions and report more symptoms than OLP/OLL patients without a concomitant defect in the FLG.

METHODS

Forty-nine Caucasian patients (42 women and 7 men, mean age 61.0 ± 10.3 years), with symptomatic OLP, OLL or stomatitis, and 29 matched healthy controls underwent a clinical oral and dermatological examination, oral mucosal biopsy and filaggrin genotyping (testing for R2447X, R501X, 2282del4). Smear tests for Candida spp. were performed in all patients to exclude oral candidiasis. Immunohistochemistry were performed using poly- and monoclonal filaggrin antibodies.

RESULTS

The immunoreactivity for filaggrin was significantly more intense in the oral mucosa in the patients with OLP/OLL compared with healthy controls (P = 0.000025). No difference was noted in the incidence of defects in the FLG and active dermatoses between patients and healthy controls. No difference was noted in extension and number of symptoms reported by patients with OLP/OLL with or without a concomitant defect in the FLG.

CONCLUSION

OLP/OLL is associated with an altered distribution of filaggrin in the oral mucosa independently of defects in the FLG. Patients with OLP/OLL did not display more active dermatoses other than cutaneous LP when compared to healthy controls.

Dysregulated function of normal human epidermal keratinocytes in the absence of filaggrin

The aim of the present study was to investigate the impact of filaggrin knockdown on the function of normal human epidermal keratinocytes (NHEKs). Filaggrin expression levels in NHEKs were knocked down by lentivirus (LV) encoding small hairpin RNA (shRNA), with control cells infected with nonsense shRNA or not infected. Cell migration and invasion were assayed using Transwell inserts, cell adhesion and proliferation by the Cell Counting kit-8 assay, and apoptosis and cell cycle progression by flow cytometry. shRNA efficiently suppressed expression of filaggrin protein. The LV group had significantly decreased cell migration, adhesion and proliferation, and increased apoptosis compared with the control groups (P=0.027). In addition, the proportion of cells in G₁ and G₂ phases were significantly increased in the LV group compared with control groups (P=0.018). The results of the present study demonstrate that filaggrin knockdown inhibits NHEK migration, adhesion and proliferation, promotes apoptosis and disturbs cell cycle progression.

Contact dermatitis in the construction industry: the role of filaggrin loss-of-function mutations

BACKGROUND

A high prevalence of contact dermatitis (CD) and respiratory symptoms has been observed in the construction industry, probably due to widespread exposure to irritants and allergens. It is unknown whether carriers of loss-of-function mutations in the gene encoding filaggrin (FLG), a known risk gene for eczema and asthma, are at increased risk.

OBJECTIVES

To investigate associations of FLG mutations with CD and respiratory symptoms in Dutch construction workers.

METHODS

A questionnaire including items on dermal and respiratory symptoms such as wheeze, shortness of breath and asthma was administered to construction workers. Total and specific serum IgE was analysed by enzyme immunoassays. Four FLG loss-of-function mutations were genotyped. CD was diagnosed by a team of a dermatologist and a clinical occupational medicine specialist using photographs of the subjects' hands and self-reported questionnaire data.

RESULTS

Of the 506 participating workers, 6·3% carried at least one FLG mutation. Mild CD was diagnosed by the specialists in 34·0%, and severe CD in an additional 24·3%. CD was considered work related in 282 of 295 subjects (95·6%). Carriers of FLG variants had an increased risk of CD compared with subjects carrying wild-type alleles [mild CD: odds ratio (OR) 5·71, 95% confidence interval (CI) 1·63-20·06; severe CD: OR 8·26, 95% CI 2·32-29·39]. FLG variants and the presence of CD were not associated with respiratory symptoms and atopy.

CONCLUSIONS

Contact dermatitis prevalence in construction workers is high. FLG loss-of-function mutations increase the risk of CD even further. FLG mutations were not associated with respiratory symptoms or atopy.

Guidelines for diagnosis, prevention and treatment of hand eczema

The guidelines aim to provide advice on the management of hand eczema (HE), using an evidence- and consensus-based approach. The guidelines consider a systematic Cochrane review on interventions for HE, which is based on a systematic search of the published literature (including hand-searching). In addition to the evidence- and consensus-based recommendation on the treatment of HE, the guidelines cover mainly consensus-based diagnostic aspects and preventive measures (primary and secondary prevention). Treatment recommendations include non-pharmacological interventions, topical, physical and systemic treatments. Topical corticosteroids are recommended as first line treatment in the management of HE, however continuous long-term treatment beyond six weeks only when necessary and under careful me-dical supervision. Alitretinoin is recommended as a second line treatment (relative to topical corticosteroids) for patients with severe chronic HE. Randomized control trials (RCT) are missing for other used systemic treatments and comparison of systemic drugs in “head-to-head” RCTs are needed.The guidelines development group is a working group of the European Society of Contact Dermatitis (ESCD) and has carefully tried to reconcile opposite views, define current optimal practice and provide specific recommendations, and meetings have been chaired by a professional moderator of the AWMF (Arbeitsgemeinschaft der Wis-senschaftlichen Medizinischen Fachgesellschaften; Association of the Scientific Medi-cal Societies in Germany).No financial support was given by any medical company. The guidelines are expected to be valid until December 2017 at the latest.

Molecular biology of atopic dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disease with specific genetic and immunological mechanisms. The rapid development of new techniques in molecular biology had ushered in new discoveries on the role of cytokines, chemokines, and immune cells in the pathogenesis of AD. New polymorphisms of AD are continually being reported in different populations. The physical and immunological barrier of normal intact skin is an important part of the innate immune system that protects the host against microbials and allergens that are associated with AD. Defects in the filaggrin gene FLG may play a role in facilitating exposure to allergens and microbial pathogens, which may induce Th2 polarization. Meanwhile, Th22 cells also play roles in skin barrier impairment through IL-22, and AD is often considered to be a Th2/Th22-dominant allergic disease. Mast cells and eosinophils are also involved in the inflammation via Th2 cytokines. Release of pruritogenic substances by mast cells induces scratching that further disrupts the skin barrier. Th1 and Th17 cells are mainly involved in chronic phase of AD. Keratinocytes also produce proinflammatory cytokines such as thymic stromal lymphopoietin (TSLP), which can further affect Th cells balance. The immunological characteristics of AD may differ for various endotypes and phenotypes. Due to the heterogeneity of the disease, and the redundancies of these mechanisms, our knowledge of the pathophysiology of the disease is still incomplete, which is reflected by the absence of a cure for the disease.

The role of filaggrin in the skin barrier and disease development

Filaggrin is a structural protein that is fundamental in the development and maintenance of the skin barrier. The function of filaggrin and its involvement in various cutaneous and extracutaneous disorders has been the subject of considerable research in recent years. Mutations in FLG, the gene that encodes filaggrin, have been shown to cause ichthyosis vulgaris, increase the risk of atopic dermatitis and other atopic diseases, and exacerbate certain conditions. The present article reviews the current knowledge on the role of filaggrin in the skin barrier, FLG mutations, and the consequences of filaggrin deficiency.

Clinical course of occupational irritant contact dermatitis of the hands in relation to filaggrin genotype status and atopy

BACKGROUND

Filaggrin loss-of-function mutations and atopy may alter the clinical course of irritant contact dermatitis (ICD).

OBJECTIVE

To investigate the clinical course of patients with occupational ICD according to loss-of-function mutations in the filaggrin gene (FLG) and atopy.

METHODS

In a prospective cohort study, the clinical course, use of topical corticosteroids, sick leave, recovery rate and job continuation were investigated in 459 inpatients treated for occupational ICD of the hands. Patients were genotyped for four FLG mutations, examined for atopy and followed for up to 3 years after discharge.

RESULTS

Our study included 327 (71·2%) atopic individuals and 132 nonatopic individuals. Overall, 68 patients showed a mutation in the FLG alleles R501X, R2447X, S3247X and 2282del4 (60 atopic and eight nonatopic). Nonatopic patients with ICD responded well to therapeutic approaches, while atopy status made subjects more resistant to therapy, resulting in lower rates of recovery and job continuation and higher use of topical corticosteroids. Carriage of FLG loss-of-function mutations in combination with atopy worsened the course. The risk of abandoning one's profession in this group was significantly increased when compared with 'pure' ICD (odds ratio 3·1) after 3 years.

CONCLUSIONS

Patients with atopy are a special risk population for ICD. In the presence of atopy, FLG mutations seem to be a modifier of the severity of the clinical course in ICD. Early-stage identification of this subgroup may result in additional emphasis to these patients regarding the importance of adherence to specific therapeutic interventions.

Ichthyosis vulgaris: the filaggrin mutation disease

Ichthyosis vulgaris is caused by loss-of-function mutations in the filaggrin gene (FLG) and is characterized clinically by xerosis, scaling, keratosis pilaris, palmar and plantar hyperlinearity, and a strong association with atopic disorders. According to the published studies presented in this review article, FLG mutations are observed in approximately 7·7% of Europeans and 3·0% of Asians, but appear to be infrequent in darker-skinned populations. This clinical review article provides an overview of ichthyosis vulgaris epidemiology, related disorders and pathomechanisms. Not only does ichthyosis vulgaris possess a wide clinical spectrum, recent studies suggest that carriers of FLG mutations may have a generally altered risk of developing common diseases, even beyond atopic disorders. Mechanistic studies have shown increased penetration of allergens and chemicals in filaggrin-deficient skin, and epidemiological studies have found higher levels of hand eczema, irritant contact dermatitis, nickel sensitization and serum vitamin D levels. When relevant, individuals should be informed about an increased risk of developing dermatitis when repeatedly or continuously exposed to nickel or irritants. Moreover, with our current knowledge, individuals with ichthyosis vulgaris should be protected against neonatal exposure to cats to prevent atopic dermatitis and should abstain from smoking to prevent asthma. Finally, they should be advised against excessive exposure to factors that decrease skin barrier functions and increase the risk of atopic dermatitis.

Atopic dermatitis 2.0: from the clinical phenotype to the molecular taxonomy and stratified medicine

Atopic dermatitis (AD) is a paradigmatic inflammatory chronic skin disease. As for other chronic skin diseases, (i) the spectrum of the clinical phenotype and severity as well as (ii) the genetic background and (iii) the underlying mechanisms strongly suggest a high degree of pathophysiological heterogeneity yet leading to a similar clinical pattern, that is, the eczematous skin lesion, but showing distinct progression patterns. This review suggests to exploit the recent knowledge about AD for a novel approach proposing a tentative first molecular taxonomy of this disease based on the genotype and endophenotype. The consequences in terms of personalized prevention and management are delineated.

Clinical presentation of atopic dermatitis by filaggrin gene mutation status during the first 7 years of life in a prospective cohort study

Background

Filaggrin null mutations result in impaired skin barrier functions, increase the risk of early onset atopic dermatitis and lead to a more severe and chronic disease. We aimed to characterize the clinical presentation and course of atopic dermatitis associated with filaggrin mutations within the first 7 years of life.

Method

The COPSAC cohort is a prospective, clinical birth cohort study of 411 children born to mothers with a history of asthma followed during their first 7 years of life with scheduled visits every 6 months, as well as visits for acute exacerbations of dermatitis. Atopic dermatitis was defined in accordance with international guidelines and described at every visit using 35 predefined localizations and 10 different characteristics.

Results

A total of 170 (43%) of 397 Caucasian children developed atopic dermatitis. The R501X and/or 2282del4 filaggrin null mutations were present in 26 (15%) of children with atopic dermatitis and were primarily associated with predilection to exposed skin areas (especially the cheeks and back of the hands) and an up-regulation of both acute and chronic dermatitis. Furthermore, we found the filaggrin mutations to be associated with a higher number of unscheduled visits (3.6 vs. 2.7; p = 0.04) and more severe (moderate-severe SCORAD 44% vs. 31%; p = 0.14), and widespread dermatitis (10% vs. 6% of the body area, p<0.001) with an earlier age at onset (246 vs. 473 days, p<0.0001) compared to wild-type.

Conclusion

In children, filaggrin mutations seem to define a specific endotype of atopic dermatitis primarily characterized by predilection to exposed areas of the body, in particular hands and cheeks, and an up-regulation in both acute and chronic morphological markers. Secondary, this endotype is characterized by an early onset of dermatitis and a more severe course, with more generalized dermatitis resulting in more frequent medical consultations.

A novel multiplex analysis of filaggrin polymorphisms: a universally applicable method for genotyping

BACKGROUND

The filaggrin protein is expressed as profilaggrin mainly in stratum granulosum cells of the epidermis. The profilaggrin gene codes for 10-12 filaggrin repeats. The filaggrin protein is important for skin barrier function. Filaggrin deficiency due to functional null-polymorphisms affects 8-10% of the people in Northern Europe and is a strong risk factor for several diseases. Here, we describe a novel method for efficient, multiplexed genotyping of variations in the profilaggrin gene.

METHODS

Five known techniques were combined: i) allele-specific PCR, ii) PCR with tagged primers, iii) asymmetric PCR, iv) multiplex PCR, and v) hybridization of single-stranded PCR products to spectrally coded microbeads carrying tag sequences as capture probes. Asymmetry of PCR was accomplished by having the tagged and allele-specific forward primers present in limiting concentrations. Asymmetry ensured that the later PCR cycles generated only single-stranded reverse-strand products. This greatly improved the assay sensitivity and allowed for simple optimization.

RESULTS

The specificity of the tags was verified with single PCR in wildtype and homozygous samples. Only the PCR products with the appropriate anti-tag hybridized to the corresponding beads, demonstrating the specificity of the signal. The hybridization signal is strongly dependent on single-stranded PCR products. After 46 PCR cycles, double-stranded products are clearly present, but only the single-stranded products generated in later cycles hybridize to the beads and elicit the strong signals that allow for unambiguous genotyping.

CONCLUSIONS

We have tested 17,000 samples for three filaggrin polymorphisms using this method, with a call rate exceeding 99% and a reagent cost of US $ 0.75 per sample. The method is universally applicable for multiplex genotyping of e.g. hereditary hemochromatosis, lactose intolerance, or cystic fibrosis.