Atopic dermatitis

Definition:

Atopic dermatitis, commonly known as eczema, is a skin eruption characterized by the presence of redness, dryness, fissures and itching. It can also be associated with crusting and the seepage of clear liquid.

Epidemiology:

It is a chronic disease characterized by skin inflammation. This condition affects about 15-30% of children and 2-10% of adults.

Atopic dermatitis begins very often in the first few months of life (45% of cases start in the first 6 months). About 60% of children will see their eczema disappear once they reach adolescence. Several of these children remain at risk for episodes during adulthood (50%).

Atopic dermatitis is part of the triad of atopic diseases: eczema, allergy and asthma. It is often the first problem to appear in what is known as the "atopic march" (followed by food allergies, asthma and allergic rhinitis).

Etiologies:

It is a problem with multifactorial and complex origins. The appearance of atopic dermatitis probably depends on a variety of genetic and environmental components.

Defects at the level of the skin barrier, as well as in the immune system, have both been observed. It is actually thought that there is a series of genetic anomalies affecting the structure and function of the epidermal barrier. The immune system plays a role in the observed inflammatory reaction.

It is important to underline the fact that atopic dermatitis is not actually caused by allergies, even though people suffering from this condition are at greater risk for developing other atopic conditions such as allergies or asthma. The same people can even see worsening of their atopic dermatitis if they subsequently develop allergies and are exposed to these allergens.

Diagnosis:

There is no specific test available for diagnosing atopic dermatitis. The doctor will rely on this diagnosis through the patient's history and skin examination. On questioning, there is the presence of a skin eruption causing itching. In fact, itching is always present in a child suffering from atopic dermatitis. In the young child unable of complaining that "it itches", parents will often still witness rubbing or scratching.

Some other elements that contribute to the diagnosis of atopic dermatitis are the presence of allergic diseases (asthma, allergic rhinitis, food allergies) in the patient themselves or a close family member. Finally, the diagnosis rests on the bodily distribution of the skin eruption. Usually in the young child, atopic dermatitis affects the cheeks and the face, but can also be found on the arms, legs and torso, rarely the buttocks. With aging, an affected patient will often see the rash appear on the folds of the elbows and behind the knees, and even the wrists and ankles; in the adult, both hands and feet can also be affected.

Management and treatment:

It must first be appreciated that atopic dermatitis is a chronic disease and that its management relies on care and treatment over the long term.

One element of the treatment is based on skin hydration. Using a mild, non-perfumed soap in short daily baths of lukewarm water in addition to generous and regular application of a moisturizing cream are at the heart of the management of atopic dermatitis. More recently, studies have demonstrated that creams containing ceramides can help in the process of skin repair.

For areas that are red and more affected, a cream or ointment with a corticosteroid base is often prescribed and must be applied before the moisturizing cream at a frequency prescribed by the treating physician. If different areas are affected, the physician might prescribe corticosteroid creams of differing concentrations. Another category of medication prescribed is the topical calcineurin inhibitors (Protopic® or Elidel®) which are often used as second-line agents.

Newer biologic therapies (regular medications typically given by injection) such as Dupixent™ (dupilumab) have also been approved to treat severe eczema in certain age groups.

It is difficult to perfectly control the itching associated with atopic dermatitis. An antihistamine, such as diphenhydramine (Bénadryl®) or hydroxyzine (Atarax®) can occasionally be helpful.

Because of the breakdown of the skin caused by eczematous lesions and by scratching, the skin of a patient with atopic dermatitis is more at risk for infection. If it is ever noted that the skin becomes redder, warmer, and in the presence of a suspicious drainage, then consultation with a physician is recommended.

Even though this is a chronic disease, it must be noted that atopic dermatitis often becomes much less severe with age in many children.

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Simon Hotte, MD FRCPC
Nha Uyen Nguyen-Luu, MD FRCPC
(translation Andrew Moore, MD FRCPC)