Atopic dermatitis (AD)

Atopic dermatitis (AD), sometimes called eczema, is a chronic dermatitis, beginning as early as the first months of life and usually found first on the face and on the extensor sides of the arms and legs are.  It is the most prevalent childhood skin disorder, with more than 10% of children afflicted in developed countries. AD is associated with hay fever and asthma.  Unlike the latter two conditions, removing an allergen such as grass, tree, or dog dander does not alleviate the condition.  The word, atopic, was chosen for its meaning: strange.

The skin in AD is erythematous and dry, and acute lesions show oozing. When AD persists after infancy, there is a predilection for the creases of the elbows and knees, the face, the neck, and the hands. Chronic lesions are thick (lichenified) and dry.  Pruritus (itching) is the main symptom and of prime importance in making the diagnosis.  Its alleviation is one of the main goals of the treatment.
The pathophysiology of AD is two-fold:

–  Impairment of the epidermal barrier function by a genetic deficiency of the protein filaggrin, of some epidermal proteases, and other epidermal proteins or lipids
– Predisposition for immediate (IgE-related) hypersensitivity to environmental allergens. Hypersensitivity to foods and/or aeroallergens does not mean that they are a cause of flares, rather that the child has an atopic background.

Treatment of AD relies on constant hydration of the skin by neutral emollients and on the treatment of acute eczematous flares by topical cortico-steroids or topical immunomodulators. Other therapeutic measures are decided on an individual basis. Intervention against food and allergenic environment is rarely beneficial.  A careful education of the patient and his/her caregivers on the disease and its treatments is useful.  Severe cases require phototherapy, and sometimes systemic treatment.

Daniel Wallach, MD
Paris, France