**1. Introduction**

168 Atopic Dermatitis – Disease Etiology and Clinical Management

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Atopic dermatitis (AD) is a chronic, relapsing and pruritic inflammatory skin disorder. The prevalence of AD has been increasing significantly in recent decades, especially in developed nations. The pathogenesis of AD is still not completely understood. AD may be the results of interactions of abnormalities of immune system, genetics, environment and epidermal barrier defects. There is a wide spectrum of clinical manifestations in AD. Accordingly, there have been a number of methods and laboratory markers to assess the severity of AD. In spite of the facts that various severity assessing criteria and laboratory markers were reported or, more or less, applied, owing to the complexity of disease, race differences and environmental uncertainties, there is disagreement about the definitions and clinical application of these criteria or markers. Nevertheless, easy and quick assessing severity methods for AD are required to guide both the daily clinical and research studies. Here, we describe some recent advances in the assessment of the severity of AD.

#### **1.1 Overview of the epidemiology of AD**

AD is a chronic, inflammatory, itchy condition that usually begins in infancy but may continue into adult life; the disease is genetically predisposed, and its expression is modified by environmental factors. The prevalence of AD is unevenly distributed worldwide, varying between 0.73-23% (Levy et al., 2003).There is a tendency of increased prevalence of AD in recent years, especially in developed industrial nations. For example, the prevalence of AD at the ages of 12-15 almost doubled in the last 20 years of 20th century in Japanese, suggesting the strong impact of environmental factors in AD development(Sugiura et al., 1998).The incidence of an infant to develop AD is 25% in three months after birth, or 50% in two years after birth, given that the mother is an AD sufferer; The incidence of AD in the offspring reaches as high as 79%, if both the parents are atopic patients, suggesting the key role of genetic predisposition in the pathogenesis of AD(Bradley er al., 2000).Key clinical manifestations of AD include itchy, dry skin, inflammatory rashes and other atopic conditions. Though not fully clarified, the clinical phenotype characterizing AD is the product of interactions between susceptibility genes, the environment, defective skin barrier function, and immunologic responses. These complex interactions would induce biological and immunological responses at cellular or molecular levels, involving the skin, immune system or even the integument as a whole.

Advances in Assessing the Severity of Atopic Dermatitis 171

SCORAD index includes objective symptoms (extent and intensity) and subjective criteria (daytime pruritus and sleep loss). The severity assessment of each items were evaluated at its average intensity. Due to that the subjective symptoms represented 20 % of total of interobserver variation, European Task Force on Atopic Dermatitis recommended severity scale based only on the objective criteria of the SCORAD index to define mild, moderate, and severe AD (Kunz, 1997). It remains to be investigated that quite some laboratory parameters obtained from the lesion, serum, and other body fluids, have no significant correlation with

Most of the severity index has been applied for a given short-term therapeutic intervention, while they are insensitive in reflecting the overall disease activity to the chronic and fluctuating course of AD. Nottingham Eczema Severity Score (NESS) was introduced to be a clinical severity score method that documents AD severity over a long -term period of 12

For evaluating the life quality in AD, Quality of Life Index for Atopic Dermatitis (QoLIAD) is designed for adults with AD based on Quality of Life (QoL)and Children's Dermatology Life Quality Index (CDLQI) for children AD. These instruments could be used to evaluate the impact degree of AD and also measure the therapeutic effect (Whalley et al., 2004; Ben-

Taken together, though well recognized and widely applied, the implementation of various scoring systems is complicated and subject to a variety of bias. Noninvasive, objective measurement has been developed and in use in recent year. The objective severity assessment of atopic dermatitis system (OSAAD) (Sugarman et al., 2003), which take advantage of instrumentations to measure water content (stratum corneum hydration, SCH), sebum content and trans-epidermal water loss (TEWL) of the skin, features the recent

OSAAD is a severity evaluation scale in AD including TEWL, SCH using a noninvasive bioengineering methods and estimation of affected body surface area (BSA). The method is suitable for both children and adults with AD compared with classical scoring system (Angelova-Fischer et al., 2005). The OSAAD score have several advantages over the clinical scoring methods. Measurement of TEWL and SCH is reproducible and reliable under given standard environment condition and instrument devices(Angelova-Fischer et al., 2005), able to evaluate quantitatively the severity scale of skin barrier impairment, sensitive to minor fluctuations in the course of AD development, and consequently applicable to assessment of treatment effects. The limitations of this technique are the inter- or intra- variability in AD patients, influenced by anatomic sites, environmental changes, etc. So the standardization of the conditions is very important in multicenter trials .There is no unified standard sites suitable for evaluation. Choi et al showed that antecubital fossa is the most favorable site for TEWL evaluation (Choi et al., 2003), while flexure surface is unsmooth. The '2 cm' site under the antecubital fossa resembles a

The skin barrier is primarily in the outer 15μm of the epidermis, the stratum corneum (SC) (Landmann, 1988). Breakdown of skin barrier is the primary event in the development of AD, which may result in atopic march (Lipozencic & Wolf, 2007) . The evaluation of skin barrier and properties is based on several variances: such as TEWL, natural moisturizing factors (NMF), skin sebum content, skin pH and skin hydration (SH). The study

SCORAD index. SCORAD index can not reflex the whole aspects of AD.

flexure and is conveniently flat for measurements (Hon et al., 2008).

**2.2 Evaluation of skin function and properties** 

months(Emerson et al., 2000; Hon et al., 2006).

development of objective evaluation of AD.

Gashir et al., 2004).
