Proceedings of the 4th Georg Rajka International Symposium on Atopic Dermatitis, Arcachon, France, September 15-17, 2005

How to Define Atopic Dermatitis?

Although atopic dermatitis (AD) is the most common skin disorder, there remains an ongoing debate on this denomination, its definition and the binary view based on immunoglobulin E measurement. The wide spectrum of the clinical phenotype of AD reflects the complex genetic and pathophysiologic mechanisms underlying the disease. The diagnostic criteria have to be reconsidered and adapted to different ethnic populations. There is an urgent need for biomarker discovery further supporting the clinical diagnostic criteria as well as the precision medicine approach on a global level.

Spontaneous atopic dermatitis is mediated by innate immunity, with the secondary lung inflammation of the atopic march requiring adaptive immunity

Background

Atopic dermatitis (AD) is an inflammatory skin condition that can occur in early life, predisposing to asthma development in a phenomenon known as the atopic march. Although genetic and environmental factors are known to contribute to AD and asthma, the mechanisms underlying the atopic march remain poorly understood. Filaggrin loss-of-function mutations are a major genetic predisposer for the development of AD and progression to AD-associated asthma.

Objective

We sought to experimentally address whether filaggrin mutations in mice lead to the development of spontaneous eczematous inflammation and address the aberrant immunologic milieu arising in a mouse model of filaggrin deficiency.

Methods

Filaggrin mutant mice were generated on the proallergic BALB/c background, creating a novel model for the assessment of spontaneous AD-like inflammation. Independently recruited AD case collections were analyzed to define associations between filaggrin mutations and immunologic phenotypes.

Results

Filaggrin-deficient mice on a BALB/c background had profound spontaneous AD-like inflammation with progression to compromised pulmonary function with age, reflecting the atopic march in patients with AD. Strikingly, skin inflammation occurs independently of adaptive immunity and is associated with cutaneous expansion of IL-5–producing type 2 innate lymphoid cells. Furthermore, subjects with filaggrin mutations have an increased frequency of type 2 innate lymphoid cells in the skin in comparison with control subjects.

Conclusion

This study provides new insights into our understanding of the atopic march, with innate immunity initiating dermatitis and the adaptive immunity required for subsequent development of compromised lung function.

Filaggrin-stratified transcriptomic analysis of pediatric skin identifies mechanistic pathways in patients with atopic dermatitis

BACKGROUND

Atopic dermatitis (AD; eczema) is characterized by a widespread abnormality in cutaneous barrier function and propensity to inflammation. Filaggrin is a multifunctional protein and plays a key role in skin barrier formation. Loss-of-function mutations in the gene encoding filaggrin (FLG) are a highly significant risk factor for atopic disease, but the molecular mechanisms leading to dermatitis remain unclear.

OBJECTIVE

We sought to interrogate tissue-specific variations in the expressed genome in the skin of children with AD and to investigate underlying pathomechanisms in atopic skin.

METHODS

We applied single-molecule direct RNA sequencing to analyze the whole transcriptome using minimal tissue samples. Uninvolved skin biopsy specimens from 26 pediatric patients with AD were compared with site-matched samples from 10 nonatopic teenage control subjects. Cases and control subjects were screened for FLG genotype to stratify the data set.

RESULTS

Two thousand four hundred thirty differentially expressed genes (false discovery rate, P < .05) were identified, of which 211 were significantly upregulated and 490 downregulated by greater than 2-fold. Gene ontology terms for "extracellular space" and "defense response" were enriched, whereas "lipid metabolic processes" were downregulated. The subset of FLG wild-type cases showed dysregulation of genes involved with lipid metabolism, whereas filaggrin haploinsufficiency affected global gene expression and was characterized by a type 1 interferon-mediated stress response.

CONCLUSION

These analyses demonstrate the importance of extracellular space and lipid metabolism in atopic skin pathology independent of FLG genotype, whereas an aberrant defense response is seen in subjects with FLG mutations. Genotype stratification of the large data set has facilitated functional interpretation and might guide future therapy development.

Experience of using peroral cosmetic products from the Emolium series in the complex therapy of children suffering from atopic dermatitis

The authors summarized the current data on the function of the epidermal barrier, mechanisms of its affection and its role in the development of atopic dermatitis. They present the results confirming the efficacy of complex administration of basic skin care products in the therapy of children suffering from atopic dermatitis. Basic skin care products were cosmetic products from the Emolium series in the form of cream and emulsion as well as skin hygiene products (bath emulsion, cream washing gel).

Mutations in the filaggrin gene in Han Chinese patients with atopic dermatitis

BACKGROUND

Recently, loss-of-function mutations in the filaggrin gene (FLG) have been identified as the cause of ichthyosis vulgaris (IV) and also predisposing factors for atopic dermatitis (AD) and AD-associated phenotypes. Until now, over thirty mutations in FLG have been identified in patients with IV and AD, but the FLG mutation spectrum is not clear for Chinese Han patients with AD. This study aimed to investigate the role of FLG mutations in AD and AD-associated phenotypes in a Chinese population.

METHODS

We carried out a comprehensive sequencing of the entire FLG coding region in 261 Han AD patients.

RESULTS

In our research, we identified ten novel mutations (R826X, 3222del4, R1140X, 4271delAA, Q1790X, 5757del4, 6834del5, 6950del8, S2706X and K4671X) and eight reported mutations (441delA, R501X, 3321delA, R1474X, Q2417X, E2422X, 7945delA and R4306X) in FLG. FLG mutations were present in 31.4% of our AD patients. Mutations 3321delA and K4671X, with a frequency of 14.6% and 9.2%, respectively, were two of the most common mutations in this AD cohort. FLG null alleles (compound genotypes) were significantly associated with AD (P < 0.001) and AD associated with food sensitization (P = 0.012). However, we did not observe a positive association between FLG mutations and other AD-associated phenotypes, including asthma, allergic rhinitis and elevated total serum IgE level.

CONCLUSION

Our study increases the total number of reported FLG mutations. Moreover, we further confirm that FLG mutations are strong predisposing factors for AD in Han Chinese.

Effects of a topically applied preparation of epidermal lipids on the stratum corneum barrier of atopic dogs

Canine atopic dermatitis (AD) is characterized ultrastructurally by disorganization of the lamellar lipids (LLs) in the stratum corneum (SC), similar to that seen in the human disease. This study, based on the examination of biopsy samples, was designed to investigate the expression of canine epidermal lipids and to evaluate quantitatively, by means of electron microscopy and ruthenium tetroxide post-fixation, the effect of a new topical skin lipid complex (SLC) on the structural deficit in the skin of five dogs with AD. The non-lesional skin of atopic dogs differed from the skin of healthy dogs in that the LLs were reduced in number and highly disorganized. After repeated applications of SLC to the non-lesional skin of dogs with AD, numerous LLs were observed in the deepest part of the SC, occupying 74% of the inter-corneocyte space, while they accounted for only 31.8% of the inter-corneocyte space in comparable biopsy samples from untreated (control) skin of the same dogs. In contrast, the LLs filled 89.5% of the deepest inter-corneocyte spaces in the SC of healthy dogs. Many keratinosomes were observed at the interface between living epidermis and SC after treatment of non-lesional AD skin. Stacks of short LL discs represented 57.6% of the total LLs found in the newly formed SC compactum in the treated atopic dogs. It is suggested that the treatment with SLC stimulated the production and secretion of endogenous SC lipids, contributing to the formation of an improved epidermal barrier.

Disease severity, scratching, and sleep quality in patients with atopic dermatitis

BACKGROUND

The relationship between sleep quality and disease severity in patients with atopic dermatitis has not been clearly defined.

METHODS

Sleep efficiency and scratching were measured over 2 nights by polysomnography, actigraphy, and self-report in 20 adults with atopic dermatitis. Tumor necrosis factor, interleukin (IL)-6, and IL-10 were assayed from a subset of 9 participants.

RESULTS

Sleep measured by actigraphy and polysomnography were strongly associated with each other. Decreased sleep efficiency was associated with increasing disease severity, scratching, and IL-6. Self-reported sleep quality and quality of life were not significantly correlated with either objective sleep measure.

LIMITATIONS

Results in this pilot study await confirmation in a larger investigation.

CONCLUSION

Objective measures but not self-report documented that increasing severity of atopic dermatitis results in more scratching and declining sleep quality. Our data also suggest an important relationship between sleep and IL-6.

Filaggrin null mutations and childhood atopic eczema: a population-based case-control study

BACKGROUND

Null mutations within the filaggrin gene (FLG) are associated with moderate-to-severe atopic eczema; their role in mild-to-moderate eczema in the general population is unknown.

OBJECTIVE

We sought to investigate the significance of 5 common FLG null mutations in childhood atopic eczema in an unselected population cohort.

METHODS

Eight hundred eleven English children aged 7 to 9 years were screened for FLG mutations. Eczema cases were defined by using United Kingdom diagnostic criteria and skin examination. Asthma and seasonal rhinitis cases were defined by parental questionnaire. Association between phenotype and genotype was investigated using Fisher exact test and logistic regression analysis.

RESULTS

The 12-month period prevalence of atopic eczema was 24.2% (95% CI, 21.2% to 27.2%), with 96% (115/120) of cases having mild-to-moderate disease. The combined null genotype (carriage of > or = 1 FLG mutations) was significantly associated with atopic eczema (P = 1.2 x 10(-4)). The odds ratio (OR) for individuals carrying 2 null mutations was 26.9 (95% CI, 3.3-217.1), but heterozygote carriers showed no significant increase in risk (OR, 1.2; 95% CI, 0.7-1.9). Eight of 190 eczema cases (4.2%) carried 2 FLG null mutations and thus might be attributed to filaggrin deficiency. Asthma in the context of eczema showed significant association with the FLG null mutations (P = 7.1 x 10(-4)). There was no association of FLG with asthma independent of eczema (P = .15) and no association with seasonal rhinitis (P = .66).

CONCLUSION

FLG null mutations are significantly associated with mild-to-moderate atopic eczema in childhood, with a recessive pattern of inheritance.

Loricrin and involucrin expression is down-regulated by Th2 cytokines through STAT-6

Atopic dermatitis (AD) is characterized by a defective skin barrier which allows increased allergen and pathogen penetration. Loricrin (LOR) and involucrin (IVL) are proteins important for skin barrier formation and integrity. In this study, we demonstrate that the gene and protein expression of LOR and IVL is significantly decreased in involved (LOR: p<0.001; IVL: p<0.001) and uninvolved (LOR: p<0.001; IVL: p<0.001) skin of AD subjects, as compared to skin from healthy subjects. Using primary keratinocytes, we further demonstrate the down-regulatory effect of IL-4 and IL-13--which are over-expressed in the skin of AD patients--on LOR and IVL expression in keratinocytes. Additionally, skin biopsies from signal transducer and activator of transcription (STAT)-6 transgenic mice were deficient in the expression and production of LOR and IVL. This study suggests that Th2 cytokines inhibit expression of LOR and IVL through a STAT-6 dependent mechanism.

Advances in allergic skin disease, anaphylaxis, and hypersensitivity reactions to foods, drugs, and insects

This review highlights some of the research advances in anaphylaxis and hypersensitivity reactions to foods, drugs, and insects and in allergic skin disease that were reported primarily in the Journal in 2006. Advances in diagnosis include identification of food proteins to which IgE binding is associated with severe reactions; elucidation of diagnostic relationships of skin prick test wheal size with outcomes of egg, tree nut, and sesame allergy; evaluation of the diagnostic utility of atopy patch testing for food; and the observation that yellow jacket sting outcomes are influenced by species. Mechanistic observations include the following: heating of birch pollen-related foods disrupts IgE binding but not T-cell epitopes; a simple imbalance of T(H)1/T(H)2 response does not explain variations in clinical expression of peanut allergy; and elucidation of the role of dendritic cells in drug hypersensitivity. With regard to treatment, a rapidly disintegrating epinephrine tablet showed promise for sublingual treatment of anaphylaxis, RNA interference techniques showed promise in creating lower-allergenic foods, and anti-IL-5 showed promise for treatment of eosinophilic esophagitis. Progress in our understanding of the immunology and the etiology of skin barrier dysfunction in atopic dermatitis has also been made. These observations will likely contribute toward optimizing management of these common allergic disorders.

Topical therapy of atopic dermatitis: Controversies from Hippocrates to topical immunomodulators

Although atopic dermatitis can be treated efficiently, there is still much controversy about the risk/benefit ratio of both topical corticosteroids and topical immunomodulators. Conflicting data may be found about the usefulness of bathing, diet regulation, and other therapeutic interventions. These controversies result in part from the persistence of Hippocratic doctrines in modern medical thinking. Humoralist and diathetic doctrines, as they pertain to eczema, are reviewed. The paradoxical worsening of oozing and the deadly hazards of hospitalization before the era of antibiotics are brought to mind. We hope that this historical review will improve the understanding of current controversies and help dermatologists to manage patients with atopic dermatitis and other chronic skin diseases.

Safety of topical calcineurin inhibitors in atopic dermatitis: evaluation of the evidence

Topical calcineurin inhibitors (pimecrolimus, Elidel, East Hanover, NJ; and tacrolimus, Protopic, Tokyo, Japan) have been approved for the use in atopic dermatitis since the year 2000. These compounds represent a relatively safe class of topical anti-inflammatory, nonsteroidal therapy. However, in January of 2006, the US Food and Drug Administration issued a black box warning on these compounds about possible concerns of increased long-term malignancy risk due to systemic immunosuppression. To date, studies from clinical trials, systemic absorption, and post-marketing surveillance show no evidence for this systemic immunosuppression or increased risk for any malignancy.

Breaking the (un)sound barrier: filaggrin is a major gene for atopic dermatitis

We have recently shown that loss-of-function mutations in the filaggrin gene, carried by about 10% of people of European ethnicity, cause ichthyosis vulgaris and are strong predisposing factors for atopic dermatitis and asthma secondary to atopic dermatitis. These results demonstrate a prominent role for the epidermal barrier in atopic disease and have important implications for the study of complex traits.