Epidemiology, clinical features, and immunology of the "intrinsic" (non-IgE-mediated) type of atopic dermatitis (constitutional dermatitis)

Immunoglobulin E- (IgE) and non-IgE-mediated reactions in the pathogenesis of atopic eczema/dermatitis syndrome (AEDS)

AEDS is a chronic, relapsing, highly pruritic inflammatory skin disease that commonly begins in childhood. Two forms of this disorder exist, i.e. an allergic (extrinsic) form and a nonallergic (intrinsic) form. There are clear genetic, humoral and cellular differences between the allergic and nonallergic forms of AEDS. The allergic variants express local IgE production in affected tissue and both allergic and nonallergic triggers play a major role in the expression of disease. The role of allergens is very important in the immunopathogenesis of AEDS. Nonimmunological triggers play a secondary modulatory role often hampering treatment effort and optimal response to therapeutic efforts.

How atopic is atopic dermatitis?

BACKGROUND

The extent to which the phenotype of atopic dermatitis (AD) is truly atopic has been the subject of much debate.

OBJECTIVE

We sought to systematically evaluate the evidence for the value of measurement of IgE antibodies in diagnosing AD and whether knowledge of IgE sensitization increases clinical diagnostic and predictive ability.

METHODS

We searched Medline from its inception until September 2003. Only studies that measured atopy as either skin prick test positivity or IgE-antibody sensitization to environmental allergens were included within a descriptive analysis. Because the small number of studies of adequate quality did not allow a formal meta-analysis, we assigned strength of evidence according to predefined quality criteria and ranked studies accordingly.

RESULTS

Inclusion of atopy as part of the diagnostic criteria for AD did not enhance the criteria's sensitivity and specificity in relation to the clinical phenotype of AD. The strength of association between atopy and AD varied significantly between hospital studies (47% to 75%; n=14 studies) and was stronger in hospital than in community populations (7.4% to 78%; n=13 studies). Whereas study quality did not have an effect on atopy prevalence in hospital populations, low atopy prevalences in community surveys were seen in less rigidly conducted studies. AD severity was positively associated with the number of positive skin prick test responses or IgE-antibody levels in 7 of 8 studies that measured both. Only one study suggested that IgE-specific sensitization to hen's egg is associated with subsequent development of AD, and 2 studies found that allergen-specific IgE sensitization in patients with AD is a prognostic marker for allergic airway disease in later life. Atopy-associated AD might also have a worse long-term prognosis than AD that is not associated with atopy.

CONCLUSION

Although atopy is clearly associated with AD, the role of IgE sensitization in AD needs further study. Current evidence suggests that up to two thirds of persons with AD are not atopic, which implies that continued use of the term atopic dermatitis is problematic. Longitudinal studies are needed to compare the treatment response and prognosis of IgE-associated and non-IgE-associated AD.

Immunophenotyping of inflammatory cells in lesional skin of the extrinsic and intrinsic types of atopic dermatitis

BACKGROUND

There is a subgroup of atopic dermatitis (AD) patients with normal total and specific IgE levels and negative skin tests towards common allergens. This form of the disease has been referred to as the 'intrinsic' form of AD. Although previous studies have demonstrated differences in the cytokine profile between the extrinsic and intrinsic subtypes, the pathogenesis of both subtypes of AD remains unclear.

OBJECTIVES

To compare the inflammatory micromilieu in both forms of AD.

METHODS

Immunophenotyping of the inflammatory cells was performed in lesional and nonlesional skin from 18 patients with extrinsic and 17 with intrinsic AD.

RESULTS

Immunohistochemical analysis revealed a high proportion of CD4+ T cells in the dermis, with a similar CD4/CD8 ratio in the two groups. The expression levels of other T-cell markers and epidermal Langerhans cells were increased in both forms of AD. Although the T-cell repertoires in the two subtypes were similar, dermal infiltration of eosinophils and eosinophil granular proteins was more prominent in the extrinsic type than in the intrinsic type. Eotaxin immunoreactivity was also significantly higher in the extrinsic subtype.

CONCLUSIONS

The data suggest that although the overall inflammatory microenvironment in the two subtypes appears to be similar, differences in T-cell cytokine production might contribute to the differential tissue eosinophilia in these subtypes.

Natural history of atopic dermatitis and its relationship to serum total immunoglobulin E in a population-based birth cohort study

We investigated the natural history of atopic dermatitis (AD) in a population-based birth cohort and assessed whether children at risk of visible eczema at 5 years of age can be identified from total immunoglobulin E (IgE) levels measured at 8, 12 and 18 months. AD data collected included a whole body examination for visible eczema at 49 months (4 years) and 61 months (5 years) of age and parent completed questionnaire data throughout their early lives. Children were divided into four groups based on their natural history of early AD: persistent (AD at 1, 6, 18, 30 and 42 months, n = 34), intermittent early onset (before 18 months of age, n = 495), intermittent late onset (18-42 months of age, n = 273) and unaffected (n = 429). Visible eczema at 5 years of age was present in 12.2% (117/957) (95% confidence interval [CI] 10.1-14.3%) of the children. Levels of total IgE at 8, 12 and 18 months of age were associated with early onset of AD, but not with AD of later onset. For all four natural history groups, the geometric mean total IgE at 12 months was higher in those who subsequently had visible eczema than those who did not. However, the degree of overlap was such that total IgE at 12 months of age was a poor predictor of eczema at age five. A cutoff point of 78 kU/l had the highest positive predictive value for visible eczema at 5 years of age of 28.6%, with a sensitivity of 12% and specificity of 95%.

Pimecrolimus: a review of its use in atopic dermatitis

Pimecrolimus (Elidel) is a topically active, nonsteroid, calcineurin inhibitor that has shown efficacy in controlling symptoms of atopic dermatitis in adult and pediatric patients. Topical pimecrolimus 1% cream is approved in the US for the short-term and intermittent long-term treatment of mild-to-moderate atopic dermatitis in non-immunocompromised patients aged >/=2 years who do not respond well to, or may have adverse effects with, conventional treatments. Pimecrolimus 1% cream is an effective and well tolerated treatment for atopic dermatitis in infants, children, adolescents, and adults. Pimecrolimus is effective at reducing the incidence of disease flares and, thus, the need for rescue treatment with topical corticosteroids. The drug also improves the health-related quality of life (HR-QOL) of children and adolescents, and improves the QOL of parents of children with atopic dermatitis. Furthermore, pimecrolimus does not cause skin atrophy, a problem commonly associated with topical corticosteroids, and is not associated with clinically relevant systemic adverse events. Thus, topical pimecrolimus 1% cream is an effective treatment option for the management of mild-to-moderate atopic dermatitis.

Differential in vivo cytokine mRNA expression in lesional skin of intrinsic vs. extrinsic atopic dermatitis patients using semiquantitative RT-PCR

BACKGROUND

A small subgroup of atopic dermatitis (AD) patients with normal serum IgE levels and without specific IgE sensitization has been termed 'intrinsic type of AD' (ADi) as a counterpart to the term 'extrinsic type of AD' (ADe). However, there are neither molecular markers nor clinically diagnostic tools for distinguishing between ADi and ADe.

OBJECTIVE

The present studies were undertaken to clarify the pathogenesis and in vivo cytokine micromilieu of ADi patients in comparison with ADe patients.

METHODS

We used semiquantitative RT-PCR to investigate the expression of various cytokines and assessed the tissue eosinophil counts in skin biopsies from both types of AD patients.

RESULTS

Although there was no significant difference of cellular infiltrates in the lesional skin between ADe and ADi patients, ADe had significantly increased tissue eosinophilia than ADi. Based on our RT-PCR, the expression patterns of cytokines could be categorized into four groups. The first group includes IL-5, IL-13, and IL-1beta, whose levels of mRNA expression were higher in both types of AD patients than non-atopic (NA) subjects, while ADe patients had even higher levels than ADi patients. The second group includes interferon-gamma (IFN-gamma), IL-12, granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-4, and IL-10, whose levels of mRNA expression were elevated in both types of AD patients without differences between ADe and ADi patients. The third group includes tumour necrosis factor-alpha (TNF-alpha), whose mRNA expression was more decreased in both types of AD patients than NA, and the fourth group includes IL-6 and transforming growth factor-beta (TGF-beta), which did not show any differences among the three groups.

CONCLUSION

These current data demonstrate that the expressions of cytokines IL-5, IL-13, and IL-1beta mRNA and the number of dermal infiltrating eosinophils are increased in ADe patients compared with ADi patients.

Allergic and nonallergic forms of atopic diseases

Atopic dermatitis, allergic rhinitis, and asthma are atopic diseases that develop on a complex genetic background, the so-called atopic diathesis. Although they target different organs, in most patients they are characterized by the presence of elevated total serum IgE levels. However, a subgroup of atopic patients exhibits normal IgE levels and mechanisms contributing to the so-called "intrinsic" or "nonallergic form" have been the matter of intensive research work in the last years. Because of the rapid advancements in the research field of atopic diseases, it now becomes possible for the first time to delineate a new disease classification of allergic and nonallergic subtypes of atopic diseases, thereby bringing hope to the clinician for a more specific treatment approach for each subgroup of these patients.

Atopy patch test reactions show a rapid influx of inflammatory dendritic epidermal cells in patients with extrinsic atopic dermatitis and patients with intrinsic atopic dermatitis

BACKGROUND

Normal human skin harbors a single epidermal dendritic cell (DC) population, the CD1a(+++)CD11b(-) Langerhans cells. In many chronic inflammatory skin diseases, the epidermal DC pool bears a second population, the CD1a(+)CD11b(+++) inflammatory dendritic epidermal cells (IDECs). Immunophenotypic, ultrastructural, and functional aspects of IDECs have been investigated in chronic untreated skin lesions of intrinsic and extrinsic atopic dermatitis (AD), contact dermatitis (CD), and psoriasis, but little is known about freshly induced early skin lesions.

OBJECTIVE

We sought to characterize enumerative and immunophenotypic changes in the epidermal DC pool during the development of eczematous skin lesions.

METHODS

The atopy patch test with aeroallergens and food-protein allergens and a conventional patch test with standard-series haptens were performed as models for early skin lesions of extrinsic and intrinsic AD and CD, respectively. After 72 hours, epidermal cell suspensions were prepared, analyzed in a standardized flow cytometric technique, and compared with the results obtained from chronic lesions.

RESULTS

The migration of IDECs into the epidermis occurs within 72 hours and is thus an early event. It continues in chronic AD, but not in chronic CD, lesions. The specific upregulation of FcepsilonRI, especially on IDECs, occurs later during formation of extrinsic but not intrinsic AD lesions. LCs were negative for Cd36 in patch test lesions, whereas in chronic skin lesions, LCs expressed Cd36.

CONCLUSION

The DC alteration during skin lesion formation can be subdivided into early and late events, with the influx of IDECs as an early event and the alteration of the DC phenotype as a late event.

Atopic dermatitis and asthma: parallels in the evolution of treatment

OBJECTIVES

To review epidemiologic correlations between asthma and atopic dermatitis (AD), identify common features in disease pathophysiology, and review steps involved in the development of asthma therapy guidelines to assess the appropriateness of a similar process and approach for AD.

METHODS

A 7-member panel representing specialists in dermatology, allergy, asthma, immunology, and pediatrics from around the United States convened to review the current literature and evolving data on AD. Participants presented reviews to the panel on the epidemiology of asthma and AD, the genetic predisposition to allergic disease, the current understanding of the immunopathophysiology of AD, interrelationships between the pathologic pathways of asthma and AD, evolving treatment concepts and options in AD, and the applicability of the asthma treatment model and how it may be adapted for guideline development for AD. Commentary and criticism were recorded for use in document preparation.

RESULTS

There are clear epidemiologic parallels in asthma and AD. Importantly, AD frequently is the first manifestation of an atopic diathesis, which occurs in genetically predisposed individuals and also includes asthma and allergic rhinitis. Up to 80% of children with AD will eventually develop allergic rhinitis or asthma later in childhood. This classic "atopic triad" has numerous pathophysiologic elements in common, including cyclic nucleotide regulatory abnormalities, immune cell alterations, and inflammatory mediators and allergic triggers. New therapeutic options that target underlying immune mechanisms are available, and their place among treatments for AD is becoming established. Guidelines of care have been developed for asthma. The panel noted that the National Institutes of Health/National Heart, Lung, and Blood Institute guidelines for diagnosis and management of asthma, first issued in 1991, had a tremendous positive impact on many aspects of asthma treatment. It not only created a heightened awareness that asthma is a disease of chronic inflammation, but it also provided unified approaches for therapy and opened new areas of basic science and clinical research. In addition, the guidelines spurred interactions among physicians of various specialties and stimulated a great quantity of research in asthma therapy. It is anticipated that AD therapy guidelines would have similar positive outcomes.

CONCLUSIONS

The panel concluded that, on the basis of current information and evolving therapeutic options, a clear rationale exists to support AD guideline development. The many parallels between AD and asthma suggest that processes and approaches used for the asthma therapy guidelines would be appropriate for AD.

Comparative analysis of mononuclear cell surface markers in atopic processes--a preliminary study

Atopic disorders are driven by the Th2 cell subset. We have determined the expression of costimulatory molecules and cell surface markers on peripheral CD4+ T cells and antigen presenting cells, in different atopic diseases, and we have also tried to correlate the expression of these markers with the severity of the disease. Cells from patients with atopic and contact dermatitis, mild or severe asthma, and symptomatic and non-symptomatic atopic rhinitis were analyzed by flow cytometry. Our results showed that CD30, CD124, and CD152 expression on CD4+ T cells was significantly higher in atopic dermatitis than in contact dermatitis patients (p < 0.05). It was interesting to observe that the cell surface expression of CD80 in T and B cells from atopic dermatitis patients was not enhanced as opposed to the other atopic diseases we analyzed. Our results suggest that there are differences in the immune mechanisms involved in the different atopic diseases, and that expression of CD30 in CD4+ T cells might be a marker of disease activity in atopic dermatitis.

New diagnostic classification of allergic skin disorders

PURPOSE OF REVIEW

To highlight the importance of one common nomenclature for allergic skin disorders.

RECENT FINDINGS

Diseases are best defined on the pathophysiological mechanisms underlying the symptoms. Although the mechanisms behind what is sometimes unfortunately referred to as 'atopic eczema' or 'atopic dermatitis' have been quite well understood for 30 years the present terms used are confusing. Over the years more than 20 different names have been used.

SUMMARY

Doctors, scientists and patients in the field of allergy must use one and the same terminology for allergic diseases or the result will be confusion. Diagnosis, prevention, treatment, patient advice, environmental relations, and the search for genetic markers are examples of areas that will be hampered by conflicting results. Strong efforts should be invested into broadly implementing the European Academy of Allergology and Clinical Immunology (EAACI) revised nomenclature for allergy.

Dichotomic nature of atopic dermatitis reflected by combined analysis of monocyte immunophenotyping and single nucleotide polymorphisms of the interleukin-4/interleukin-13 receptor gene: the dichotomy of extrinsic and intrinsic atopic dermatitis

Patients with atopic dermatitis display substantial immunologic abnormalities, among which elevated total IgE is considered as a hallmark; however, a subgroup of atopic dermatitis patients exhibits normal IgE levels, but mechanisms contributing to the so-called "intrinsic" or "nonallergic" form of atopic dermatitis are obscure. In order to unravel similarities and differences of both atopic dermatitis subtypes, the phenotype of monocytes, total serum IgE levels, and serum levels of cytokines regulating the IgE production from nonatopic individuals and patients with allergic rhinitis, and extrinsic and intrinsic atopic dermatitis were measured. Concomitantly, genomic DNA probes of all subjects were analyzed for single nucleotide polymorphisms of candidate genes of structures involved in the regulation of the IgE synthesis, such as interleukin-4 and the interleukin-4R/interleukin-13R. Our data show that the surface expression of the high- and low-affinity receptor for IgE (FcepsilonRI and FcepsilonRII/CD23) and the interleukin-4Ralpha chain were significantly elevated in monocytes from patients with extrinsic atopic dermatitis. Furthermore, serum levels of interleukin-13 were significantly increased in patients with intrinsic atopic dermatitis. In addition, the frequency of the interleukin-4Ralpha polymorphism C3223T and the interleukin-4 polymorphism C590T tended to be higher in extrinsic atopic dermatitis than in intrinsic atopic dermatitis. Altogether our findings indicate that intrinsic atopic dermatitis patients exhibit phenotypic and immunologic features, which differ from those of patients with extrinsic atopic dermatitis or other atopic disorders.

Peripheral blood mononuclear cells from IgE- and non-IgE-associated allergic atopic eczema/dermatitis syndrome (AEDS) demonstrate increased capacity of generating interleukin-13 but differ in their potential of synthesizing interferon-gamma

BACKGROUND

A subgroup of patients with allergic atopic eczema/dermatitis syndrome (AEDS) are known to have normal total and specific IgE levels and negative skin prick tests towards common environmental allergens. This form of the disease has been termed non-IgE-associated allergic AEDS. Although allergic mechanisms appear to be important, the pathogenesis of both IgE- and non-IgE-associated forms of the disease is unknown.

METHODS

We have compared the cytokine production pattern of peripheral blood mononuclear cells (PBMC) from IgE-associated AEDS, non-IgE-associated AEDS, and normal control individuals. PBMC were stimulated with anti-CD3 and/or anti-CD28 monoclonal antibodies (mAb) and cytokine production was measured by immunoassays in supernatants of 24-h cultures.

RESULTS

Compared to healthy subjects and non-IgE-associated AEDS patients, stimulated PBMC from IgE-associated AEDS patients produced less interferon (IFN)-gamma. However, stimulated PBMC from both IgE-associated AEDS and non-IgE-associated AEDS patients produced more interleukin (IL)-13 than PBMC from control individuals. Moreover, IL-5 production was significantly increased in non-IgE-associated AEDS but not in IgE-associated AEDS patients.

CONCLUSIONS

The underlying mechanism leading to increased differentiation of T helper (Th) 2 cells may involve a deficient capacity in producing IFN-gamma in IgE-associated AEDS but not in non-IgE-associated AEDS patients. IL-13 may be a key cytokine in the pathogenesis of both allergic forms of AEDS.

A revised nomenclature for allergy. An EAACI position statement from the EAACI nomenclature task force

This report has been prepared by an EAACI task force representing the five EAACI Sections and the EAACI Executive Committee composed of specialists that reflect the broad opinion on allergy expressed by various clinical and basic specialties dealing with allergy. The aim of this report is to propose a revised nomenclature for allergic and related reactions that can be used independently of target organ or patient age group. The nomenclature is based on the present knowledge of the mechanisms which initiate and mediate allergic reactions. However, the intention has not been to revise the nomenclature of nonallergic hypersensitivity.

A revised nomenclature for allergy. An EAACI position statement from the EAACI nomenclature task force

This report has been prepared by an EAACI task force representing the five EAACI Sections and the EAACI Executive Committee composed of specialists that reflect the broad opinion on allergy expressed by various clinical and basic specialties dealing with allergy. The aim of this report is to propose a revised nomenclature for allergic and related reactions that can be used independently of target organ or patient age group. The nomenclature is based on the present knowledge of the mechanisms which initiate and mediate allergic reactions. However, the intention has not been to revise the nomenclature of nonallergic hypersensitivity.