Asthma's Predecessor: Atopic Dermatitis

By Sarah Lebo

Asthma has an inconvenient red flag that precedes it in many pediatric cases: atopic dermatitis. Approximately half of all babies diagnosed with atopic dermatitis go on to develop asthma.¹

"Eczema can often be the presenting factor that leads you to an asthma diagnosis," said Sheila Driver, NP, a pediatric nurse practitioner at Southport Pediatrics in Lenior, N.C. "Eczema usually flares in babies. While some people outgrow it, I see 50% to 60% of those patients develop asthma and published data show that percentage as well."

Driver describes this tendency as an allergic cascade over the immune system, and she considers it one of several "A's" nurse practitioners can lump together: allergies, asthma, atopic dermatitis, anaphylaxis and acid reflux. "If you have a patient with one of those common denominators, you should look for another," she said. "Research has definitely shown a correlation."

The connection between atopic dermatitis and asthma is sometimes referred to as the atopic march - a natural progression of allergic or atopic manifestations associated with an increased production of IgE antibodies to common food and environmental allergens. Skin sensitization can be the first sign of abnormal autoimmune reactions that can lead to airway sensitization (asthma).²

Also known as eczema, atopic dermatitis causes dry, easily irritated, scaly, thick skin. Symptoms include itching, disruption of sleep and reduction in quality of life.

"The nature of the disease is that not only the skin is affected, but many aspects of life," said Noreen Nicol, NP, chief clinical officer and chief nursing officer at National Jewish Medical and Research Center, an organization of experts recognized nationally and internationally for its work in atopic dermatitis.

School and work absenteeism, occupational disability and emotional stress are common in the lives of atopic dermatitis patients and their families, Nicol points out. "In the child with eczema, the disruption to the parent's life can be just as or more severe than for the child. Thus, atopic dermatitis significantly impacts quality of life."

Along with asthma, atopic dermatitis has been steadily increasing in prevalence and severity. It now affects 20% of children in the United States.1 Changes in the environment can elicit the associated itch sensation, which results in a flare similar to the airway hyperreactivity that leads to wheezing in asthma.

"Atopic dermatitis is associated with a marked decrease in skin barrier function due to the downregulation of cornified envelope genes (filaggrin and loricrin), reduced ceramide levels, increased levels of endogenous proteolytic enzymes, and enhanced transepidermal water loss," Nicol said.

Fortunately, the majority of patients with atopic dermatitis outgrow this inflammatory skin disease.

Drastic Repercussions
There is some speculation that if the quest to quell atopic dermatitis leads to a long-term treatment, the result may reduce asthma risk. For this reason, providers should view infants with atopic dermatitis as a target group for asthma prevention.

Atopic dermatitis can be treated with adequate skin moisturizing, control of pruritis and infections, topical anti-inflammatory medications, and elimination of irritants and allergens.

"Both of these diseases rely on levels of control, not a cure," Driver said about asthma and atopic dermatitis.

Driver sometimes prescribes pimecrolimus (Elidel) and tacrolimus (Protopic) for mild cases of atopic dermatitis. For more severe cases, she finds steroid preparations more effective (mometasone [Elocon], hydrocortisone 0.2% [Westcort], triamcinolone 0.5% [Kenalog or Aristocort]). She most frequently prescribes a compounded formulation.

"I've had the most success treating babies with eczema with a mixture of absorber base - a really thick emollient - and then I mix it 1:1 with 2.5% hydrocortisone cream, so it ends up being a little bit stronger than the over-the-counter mixtures," she said. "I worked with a physician who had great success with this recipe, so I've taken it with me and patients love it."

Nicol favors commercially available products. "There is no evidence that a commercially available pound jar of hydrocortisone 1% cream or ointment won't work just as well as a compound," she said. "There are downsides to compounding products that NPs must be cognizant of: inconsistency in vehicle and drug availability, formula dependence and cost. I emphasize good basic dry skin care above all."

The Root Cause
Choosing between the two therapy approaches might not be necessary if improved treatments come along. Recent research has identified the gene defect responsible for atopic dermatitis and asthma, providing a target for where treatment might be headed. In March 2006, a team of researchers from Dundee University in the United Kingdom announced that they had identified the gene that produces filaggrin, the protein that prevents skin dryness.³

Other research has underscored the need for a temporary, artificial barrier to block incoming allergens from the skin. Keeping allergens from penetrating the skin would keep the immune system from overstimulating cell growth, giving the skin time to recreate a normal barrier.⁴ Current therapies for atopic dermatitis principally focus on suppressing the immune system, but the medicines used can produce undesired side effects.⁴

These genetic studies are prompting researchers to focus on turning down the immune response, as well as restoring a normal skin barrier to keep the outside world out of the body.

"The barrier function of epithelial surfaces is important in all tissues that have contact with the outside world. In addition to the skin and respiratory tract, it is important for the gastrointestinal tract and the ocular surface," said Ali Djalilian, MD, a faculty member at the University of Illinois in Chicago and lead author of a recently published paper on the need for a skin barrier. "These findings underline the importance of this barrier function and suggest a new strategy for restoring it in human diseases."⁴

Control is important for overall quality of life, as well as for prevention of asthma.

"Atopic dermatitis often exacerbates other ailments," Driver notes. "A child with eczema who gets chickenpox may present a worse case than a child without eczem. Since the skin is already dry and itchy, chickenpox or exposure to poison ivy or poison oak will cause a much more exaggerated response.

"Also, children with atopic dermatitis are more prone to skin infections because they often scratch, stimulating a Staph or a Strep infection in their skin."

Sarah Lebo is the associate editor. Reach her at slebo@merion.com.

References
1. Shamssain MH, Shamsian N. Prevalence and severity of asthma, rhinitis, and atopic eczema: the North East Study. Arch Dis Child. 1999;81:313-317.
2. Boguniewicz M, Leung DYM. Atopic dermatitis. J Allergy Clin Immunol. 2006;117(Suppl 2):S475-S480.
3. Palmer CN, et al. Common loss-of-function variants of the epidermal barrier protein filaggrin are a major predisposing factor for atopic dermatitis. Nat Genet. 2006;38(4):441-446.
4. Djalilian AR, et al. Connexin 26 regulates epidermal barrier and wound remodeling and promotes psoriasiform response. J Clin Invest. 2006;116:1243-1253.