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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 151-1 and 151-2). 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.

FIGURE 151-1

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

FIGURE 151-2

Atopic dermatitis on the leg of the infant in Figure 151-1. The coinlike pattern is that of nummular eczema. (Reproduced with permission from Milgrom EC, Usatine RP, Tan RA, et al: Practical Allergy. Philadelphia, PA: Elsevier; 2004.)


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.


Eczema, atopic eczema.


  • 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 151-3).1

  • It is estimated that 2% to 3% of the adult population is affected.3

FIGURE 151-3

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


  • 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. This bacterium has been found on more than 90% of adults with the disease, and only 5% of nonaffected adults.4

  • 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 151-4) or bacteria (widespread impetigo). They are also at risk of a bad ...

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