Eczematous Disorders

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Chapter 647 Eczematous Disorders

Eczematous skin disorders are characterized by exudation, lichenification, and pruritus. Acute eczematous lesions demonstrate erythema, weeping, oozing, and the formation of microvesicles within the epidermis. Chronic lesions are generally thickened, dry, and scaly, with coarse skin markings (lichenification) and altered pigmentation. Many types of eczema occur in children; the most common is atopic dermatitis (Chapter 139), although seborrheic dermatitis, allergic and irritant contact dermatitis, nummular eczema, and vesicular hand and foot dermatitis (dyshidrosis) are also relatively common in childhood.

Once the diagnosis of eczema has been established, it is important to classify the eruption more specifically for proper management. Pertinent historical data often provide the clue. In some instances, the subsequent course and character of the eruption permit classification. Histologic changes are relatively nonspecific, but all types of eczematous dermatitis are characterized by intraepidermal edema known as spongiosis.

647.1 Contact Dermatitis

The form of eczema known as contact dermatitis can be subdivided into irritant dermatitis, resulting from nonspecific injury to the skin, and allergic contact dermatitis, in which the mechanism is a delayed hypersensitivity reaction. Irritant dermatitis is more frequent in children, particularly during the early years of life.

Irritant contact dermatitis can result from prolonged or repetitive contact with various substances that include saliva, citrus juices, bubble bath, detergents, abrasive materials, strong soaps, and proprietary medications. Saliva is probably one of the most common offenders; it may cause dermatitis on the face and in the neck folds of a drooling infant or a retarded child. In older children who habitually lick their lips because of dryness, frequently without being aware, a striking, sharply demarcated perioral rash may develop (Fig. 647-1). Among the exogenous irritants, citrus juices, proprietary medications, and bubble bath preparations are relatively common. Excessive accumulation of sweat and moisture as a result of wearing occlusive shoes may also cause irritant dermatitis.

Irritant contact dermatitis may be indistinguishable from atopic dermatitis or allergic contact dermatitis. A detailed history and consideration of the sites of involvement, the age of the child, and contactants usually provide clues to the etiologic agent. The propensity for development of irritant dermatitis varies considerably among children; some may respond to minimal injury, making it difficult to identify the offending agent through history. Irritant contact dermatitis usually clears after removal of the stimulus and temporary treatment with a topical corticosteroid preparation (Chapter 638). Education of patients and parents about the causes of contact dermatitis is crucial to successful therapy.

Diaper dermatitis can be regarded as the prototype of irritant contact dermatitis. As a reaction to overhydration of the skin, friction, maceration, and prolonged contact with urine and feces, retained diaper soaps, and topical preparations, the skin of the diaper area may become erythematous and scaly, often with papulovesicular or bullous lesions, fissures, and erosions (Fig. 647-2). The eruption can be patchy or confluent, but the genitocrural folds are often spared. Chronic hypertrophic, flat-topped papules and infiltrative nodules may occur. Secondary infection with yeast is common. Discomfort may be marked because of intense inflammation. Allergic contact dermatitis, seborrheic dermatitis, psoriasis, candidosis, atopic dermatitis, and rare disorders such as Langerhans cell histiocytosis (histiocytosis X) and acrodermatitis enteropathica should be considered when the eruption is persistent or is recalcitrant to simple therapeutic measures.

Diaper dermatitis often responds to simple measures; some infants are predisposed to diaper dermatitis, and management may be difficult. The damaging effects of overhydration of the skin and prolonged contact with feces and urine can be obviated by frequent changing of the diapers. Over-washing should be avoided because it leads to chapping and a worsening of the dermatitis. Disposable diapers containing a superabsorbent material may help maintain a relatively dry environment. Frequent topical applications of a bland protective barrier agent (petrolatum or zinc oxide paste) may suffice to prevent dermatitis. Candidal infection is signified by red-pink tender skin that has numerous 1- to 2-mm pustules and papules at the periphery of the dermatitis. Treatment with a topical anticandidal agent may be helpful.

Juvenile plantar dermatosis is a common form of irritant contact dermatitis occurring mainly in prepubertal children. The dermatitis characteristically involves the weight-bearing surfaces, may be pruritic or painful, and causes a glazed appearance of the plantar skin (Fig. 647-3). Fissuring may become extensive, producing considerable discomfort. The dermatitis results from alternating excessive hydration and rapid moisture loss, which cause chapping of the skin and cracking of the stratum corneum. Affected children often have hyperhidrosis, wear occlusive synthetic footwear, and subject their feet to rapid drying without moisturization. Immediate application of a thick emollient when socks and shoes are removed or immediately after swimming usually minimizes this condition. Severe inflammatory cases may require short-term (1-2 wk) application of a medium- to high-potency topical steroid.

Allergic contact dermatitis is a T cell–mediated hypersensitivity reaction that is provoked by application of an antigen to the skin surface. The antigen penetrates the skin, where it is conjugated with a cutaneous protein, and the hapten-protein complex is transported to the regional lymph nodes by antigen-presenting Langerhans cells. A primary immunologic response occurs locally in the nodes and becomes generalized, presumably because of dissemination of sensitized T cells. Sensitization requires several days and, when followed by a fresh antigenic challenge, manifests as allergic contact dermatitis. Generalized distribution may also occur if enough antigen finds its way into the circulation. Once sensitization has occurred, each new antigenic challenge may provoke an inflammatory reaction within 8-12 hr; sensitization to a particular antigen usually persists for many years.

Acute allergic contact dermatitis is an erythematous, intensely pruritic, eczematous dermatitis, which, if severe, may be edematous and vesiculobullous. The chronic condition has the features of long-standing eczema: lichenification, scaling, fissuring, and pigmentary change. The distribution of the eruption often provides a clue to the diagnosis. Volatile sensitizers usually affect exposed areas, such as the face and arms. Jewelry, topical agents, shoes, clothing, henna tattoo dyes, and plants cause dermatitis at points of contact.

Rhus dermatitis

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