Dermatitis
An inflammation of the skin, dermatitis occurs in several forms: atopic (discussed here), seborrheic, nummular, contact, chronic, localized neurodermatitis (lichen simplex chronicus), exfoliative, and stasis. (See Types of dermatitis, pages 260 to 263.)
Atopic dermatitis (atopic or infantile eczema) is a chronic or recurrent inflammatory response commonly associated with other atopic diseases, such as bronchial asthma and allergic rhinitis. It usually develops in infants and toddlers between ages 1 month to 1 year, commonly in those with strong family histories of atopic disease. These children usually acquire other atopic disorders as they grow older.
Typically, this form of dermatitis flares and subsides repeatedly before finally resolving during adolescence. However, it can persist into adulthood. Atopic dermatitis affects about 9 out of every 1,000 persons.
Causes
The cause of atopic dermatitis is unknown, but there is a genetic predisposition exacerbated by such factors as food allergies, infections, irritating chemicals, temperature and humidity, and emotions. Approximately 10% of childhood cases are caused by allergy to certain foods, particularly eggs, peanuts, milk, and wheat.
Atopic dermatitis tends to flare up in response to extremes in temperature and humidity. Other causes of flare-ups are sweating and psychological stress.
An important secondary cause of atopic dermatitis is irritation, which seems to change the epidermal structure, allowing immunoglobulin (Ig) E activity to increase. Consequently, chronic skin irritation usually continues even after exposure to the allergen has ended or after the irritation has been systemically controlled.
Signs and symptoms
Atopic skin lesions generally begin as erythematous areas on excessively dry skin. In children, such lesions typically appear on the forehead, cheeks, and extensor surfaces of the arms and legs; in adults, at flexion points (antecubital fossa, popliteal area, and neck).
During flare-ups, pruritus and scratching cause edema, crusting, and scaling. Eventually, chronic atopic lesions lead to multiple areas of dry, scaly skin, with white dermatographia, blanching, and lichenification.
Common secondary conditions associated with atopic dermatitis include viral, fungal, or bacterial infections and ocular disorders.
Because of intense pruritus, the upper eyelid is commonly hyperpigmented and swollen, and a double fold occurs
under the lower lid (Morgan’s, Dennie’s, or Mongolian fold). Atopic cataracts are unusual but may develop between the ages of 20 and 40.
under the lower lid (Morgan’s, Dennie’s, or Mongolian fold). Atopic cataracts are unusual but may develop between the ages of 20 and 40.
Kaposi’s varicelliform eruption (eczema herpeticum), a potentially serious widespread cutaneous viral infection, may develop if the patient comes in contact with a person who is infected with herpes simplex.
Diagnosis
A family history of atopic disorders is helpful in the diagnosis of atopic dermatitis.
Typical distribution of skin lesions and course rule out other inflammatory skin lesions, such as diaper rash (lesions confined to the diapered area), seborrheic dermatitis, and chronic contact dermatitis (lesions affect hands and forearms, sparing antecubital and popliteal areas). Serum IgE levels are commonly elevated but aren’t diagnostic.
Treatment
Effective treatment of atopic lesions consists of eliminating allergens and avoiding irritants (strong soaps, cleansers, and other chemicals), extreme temperature changes, and other precipitating factors. Local and systemic measures relieve itching and inflammation.
Clinical TipPrevention of excessive dryness of the skin is critical to successful therapy.
Topical application of a cortico-steroid ointment, especially after bathing, usually alleviates inflammation. Between steroid doses, application of a moisturizing cream can help retain moisture. Systemic corticosteroid therapy should be used only during extreme exacerbations.
Weak tar preparations and ultraviolet B light therapy are used to increase the thickness of the stratum corneum. Antibiotics are appropriate for crusted and weeping lesions.
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