Atopic dermatitis is a chronic disorder characterized by xerosis, pruritus, scaly erythematous patches, and thickening of the skin with enhancement of normal skin markings (lichenification). It is frequently associated with a personal or family history of hay fever, asthma, or allergic rhinitis. It can be divided into three phases based on the age of the individual: infantile, childhood, and adolescent.
Although many patients and families will insist on “finding the cause,” experience and studies confirm that specific allergen identification and avoidance or dietary modification is less helpful than focusing on skin treatment and maintaining healthy skin barrier function.
AGE Onset usually from age 2 to 12 months, and almost all cases by age 5 years. Nearly 80% of cases will resolve by adulthood.
INCIDENCE Common and thought to be increasing.
HEREDITARY PREDISPOSITION More than two-thirds have personal or family history of allergic rhinitis, hay fever, or asthma. Many children with atopic dermatitis develop asthma and/or hay fever later in life.
PREVALENCE 10% to 15% of the childhood population with significant regional variability. Up to 11% of the US pediatric population affected.
The cause of atopic dermatitis is unknown; however, multiple factors are known to play a role in the development of atopic dermatitis. Certain genetic factors (such as filaggrin gene abnormalities) may lead to xerosis while others may result in immune dysregulation. Factors such as stress, climate, infections, irritants, and allergens seem to play a role in many patients as well. For the vast majority of patients, there is no one “trigger” or “cause,” but rather an unfortunate collection of constituents that all can worsen the disease. A central tenet in the pathophysiology of atopic dermatitis is believed to be the interplay between epidermal disruption and inflammation mediated by T-cells and Langerhans cells.
Atopic dermatitis is sometimes called “the itch that rashes.” Dry skin and pruritus are found in essentially all patients. Scratching the skin leads to the characteristic eczematous changes and a vicious itch-scratch cycle. Itching may be aggravated by cold weather, frequent bathing (particularly with hot water), wool, detergent, soap, and stress. The disease can wax and wane unpredictably, however, which probably contributes to the numerous misattributions of causes and remedies.
TYPE Patches and plaques with scale, crust, and lichenification. Lesions usually confluent and ill defined.
Special Clinical Features
Atopic children may demonstrate increased palmar markings, periorbital atopic pleats (Dennie–Morgan lines), keratosis pilaris, or white dermatographism. They also can develop widespread herpetic, wart, molluscum, or tinea infections because of their impaired skin barrier function.