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Patient Storyx
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A 1-year-old Asian American girl is brought to her family physician for a new rash on her face and legs (Figures 130-1 and 130-2). The child is scratching both areas but is otherwise healthy. There is a family history of asthma, allergic rhinitis, and atopic dermatitis (AD) on the father’s side. The child responded well to low-dose topical corticosteroids and emollients.

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FIGURE 130-1

Atopic dermatitis on the cheeks of an infant. (Used with permission from Milgrom EC, Usatine RP, Tan RA, Spector SL. Practical Allergy. Philadelphia, PA: Elsevier; 2004.)

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FIGURE 130-2

Atopic dermatitis on the leg of the infant in Figure 130-1. The coin-like pattern is that of nummular eczema. (Used with permission from Milgrom EC, Usatine RP, Tan RA, Spector SL. Practical Allergy. Philadelphia, PA: Elsevier; 2004.)

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Introduction
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AD is a chronic and relapsing inflammatory skin disorder characterized by itching and inflamed skin that is triggered by the interplay of genetic, immunologic, and environmental factors.

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Synonyms
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Eczema, atopic eczema.

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Epidemiology
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  • AD is the most frequent inflammatory skin disorder in the US and the most common skin condition in children.1

  • Worldwide prevalence in children is 15 to 20 percent and is increasing in industrialized nations.2

  • Sixty percent of cases begin during the first year of life and 90 percent by 5 years of age.1 1/3 will persist into adulthood.2

  • Sixty percent of adults with AD have children with AD (Figure 130-3).1

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FIGURE 130-3

The child and his mother both have atopic dermatitis but not in the most typical distribution. (Used with permission from Richard P. Usatine, MD.)

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Etiology and Pathophysiology
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  • Strong familial tendency, especially if atopy is inherited from the maternal side.

  • Associated with elevated T-helper (Th) 2 cytokine response, elevated serum immunoglobulin (Ig) E, hyperstimulatory Langerhans cells, defective cell-mediated immunity, and loss of function mutation in filaggrin, an epidermal barrier protein.

  • Exotoxins of Staphylococcus aureus act as superantigens and stimulate activation of T-cells and macrophages, worsening AD without actually showing signs of superinfection.

  • Patients may have a primary T-cell defect. This may be why they can get more severe skin infections caused by herpes simplex virus (eczema herpeticum as seen in Figure 130-4) or bacteria (widespread impetigo). They are also at risk of a bad reaction to the smallpox vaccine with dissemination of the attenuated virus beyond the vaccination site. Eczema vaccinatum is a potentially deadly complication of smallpox vaccination (Figure 130-5).

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