Porth's Essentials of Pathophysiology, 4e

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Integumentary Function

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water loss and dry skin; and immunoglobulin E (IgE)- mediated sensitization to food and environmental anti- gens. 27,28 Whether the primary defect is dermatologic or immunologic is uncertain. It has been suggested that the epidermal barrier disturbance allows increased antigen absorption and contributes to the hyperreactivity char- acteristic of atopic dermatitis. 27,28 The lesions of atopic dermatitis are usually character- ized by erythematous papules and vesicles, erosions, and serous exidates. Scratching causes crusted erosions. The clinical manifestations of the disorder often vary with age. In infancy the eczematous lesion usually appear on the cheeks and scalp (Fig. 46-13). The skin of the cheeks may be paler, with extra creases under the eyes, called Dennie-Morgan folds . During childhood, lesions involve flexures in the nape of the neck, and the dorsal aspects of the limbs. Adolescents and adults usually have dry, red patches affecting the face, neck, and upper trunk. The bends of the elbows and knees are usually involved. In chronic cases, the skin is dry, leathery, and lichenified. Persons with dark skin may have a papular eruption and poorly demarcated hypopigmentation patches on the cheeks and extremities. In persons with black skin, pigmen- tation may be lost from lichenified skin. Acute flares may present with red patches that are weepy, shiny, or lichenified, and with plaques and papules. Itching may be severe and prolonged with both childhood and adult forms of atopic dermatitis. Secondary infections are common. Treatment is designed to target the underlying abnormalities: dryness, pruritus, infection, and inflam- mation. 29 Basic therapy begins with optimal skin care, addressing the skin barrier defect with continuous use of emollients and skin hydration, along with avoiding exposure to irritants such as wool clothing, soaps, and hot water. Topical corticosteroids remain an important treat- ment for acute flare-ups but can cause local and sys- temic side effects. Potency of topical corticosteroids is

classified by the potential for vasoconstriction. In gen- eral, only preparations that have weak or moderate potency are used on the face and genital areas, whereas those that have moderate or high potency are used on other areas of the body. Lower-potency corticosteroids may be sufficient on all areas of the body in younger children. One of the main concerns of topical corticoste- roid use is skin thinning. Another concern is secondary adrenal suppression and the suppression of growth in children resulting from systemic absorption. Wet-wrap therapy, in which a wet dressing is applied over emol- lients in combination with topical antiseptics or topical corticosteroids, has been shown to be beneficial in some cases of severe atopic dermatitis. Elimination of aller- gens in the living environment is a hallmark of therapy. Systemic or adjuvant therapy is usually reserved for severe acute exacerbations. Short-term corticoste- roids are also used during acute flare-ups in adults. Antihistamines may be used to relieve itching. Secondary infection with S. aureus is common and may be treated with systemic antimicrobial therapy. Phototherapy can be an important adjunct for severely affected adults and adolescents older than 12 years of age. Urticaria Urticaria, or hives, is a common skin disorder character- ized by the development of edematous wheals accompa- nied by intense itching. 30,31 The lesions typically appear as raised pink or red areas surrounded by a paler halo (Fig. 46-14). They blanch with pressure and vary in size from a few millimeters to centimeters. Angioedema, which can occur alone or with urticaria, is character- ized by nonpitting, nonpruritic, well-defined edematous swelling that involves subcutaneous tissues of the face, hands, feet, or genitals. It is more likely than urticaria to produce life-threatening swelling of the tongue and upper airways. Urticaria can be acute or chronic and due to known or unknown causes. Numerous factors, both immunologic

FIGURE 46-14. Urticarial drug eruption. Note the bizarre shapes of the urticarial plaques. (From Goodheart HP. Goodheart’s Photoguide to Common Skin Disorders. Philadelphia, PA: Wolters Kluwer Health | Lippincott Williams & Wilkins; 2009:298.)

FIGURE 46-13. Atopic dermatitis.The cheeks are a typical location in an infant. (From Goodheart HP. Goodheart’s Photoguide to Common Skin Disorders. Philadelphia, PA: Wolters Kluwer Health | Lippincott Williams &Wilkins; 2009:52.)