Chapter 93

#### High-Yield Facts

• Atopic dermatitis affects 10% to 20% of children and 60% to 70% of cases remit by 15 years of age.

• Typical patterns of eczematous rash occur based on the age of the patient—extensor surfaces of the extremities, cheeks, and scalp for young children; flexor surfaces of the extremities for older children.

• Nickel allergy is the most common identifiable cause of allergic contact dermatitis.

• Irritant diaper dermatitis occurs on the convex surfaces of skin in the diaper area, while fungal diaper dermatitis occurs in the concave surfaces with satellite papules on the adjacent skin.

• Most cases of dermatitis, regardless of cause, respond to topical steroids and removal of causative agent. Rarely, systemic steroids are needed to bring inflammation under control.

#### Atopic Dermatitis

##### Etiology

Atopic dermatitis (AD), also known as eczema, is a very common inflammatory skin condition affecting approximately 10% to 20% of children. It usually presents in the first 6 months of life, and 60% to 70% of cases remit by 15 years of age.1 Over 50% of children with AD have been shown to have sensitization to a food or aeroallergen. However, the clinical relevance of these food allergens are not well defined enough to recommend elimination diets.2 Children with AD are also at risk of developing asthma, and allergic rhinitis.

##### Pathophysiology

AD results from the primary problem of dry skin, perhaps arising from a defective skin barrier in the stratum corneum. This defect in skin integrity places the child at risk for skin infection with bacteria, fungi, and viruses. Furthermore, dry skin becomes pruritic and inflammation results after persistent itching.

##### Recognition

Clinical manifestations vary with the age of the patient. Infants may present with symmetric dry red patches or vesicles on the cheeks, scalp, trunk, and flexor and extensor surfaces of extremities. Scratching can lead to weeping lesions, lichenification, or crusted erosions (Figs. 93-1 and 93-2). Older children tend to have lesions on the flexural areas of the extremities, face, neck, and dorsum of hands and feet. Nummular (“coin shaped”) eczema usually manifests as round, extremely pruritic lesions on the extremities (Fig. 93-3). Eczema herpeticum is a condition that occurs when Herpes simplex virus (HSV) infection penetrates the skin through the already impaired barrier affected by an eczematous lesion (Fig. 93-4). It is commonly coinfected with Staphylococcus aureus. AD is usually a clinical diagnosis made by typical patterns of lesions and symptoms.

###### FIGURE 93-1

A: and B: Extensor distribution of atopic dermatitis in an infant.

###### FIGURE 93-2

A: and B: Flexor distribution of eczema in an infant.

###### FIGURE 93-3

A 9-year-old ...

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