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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 145-1 and 145-2). 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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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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- AD is the most frequent inflammatory skin disorder in the United States and the most common skin condition in children.1
- Worldwide prevalence in children is 15% to 20% and is increasing in industrialized nations.2
- Sixty percent of cases begin during the first year of life and 90% by 5 years of age.1 One third will persist into adulthood.2
- Sixty percent of adults with AD have children with AD (Figure 145-3).1
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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 145-4) 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 145-5).
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