Pediatric Annals

CME Article 

Atopic Dermatitis: Recent Findings and Insights

Wynnis L. Tom, MD

Abstract

Wynnis L. Tom, MD, is Assistant Professor of Pediatrics and Medicine, Dermatology, University of California, San Diego, and Rady Children’s Hospital, San Diego, CA.

Dr. Tom has disclosed no relevant financial relationships.

Address correspondence to: Wynnis L. Tom, MD, fax: 858-966-4040; email: wtom@rchsd.org.

A topic dermatitis, often called “eczema,” is one of the most common chronic conditions affecting children (see Figure 1). The associated itch, inflammation, and sleep loss have a profound effect on the quality of life of the child, as well as on family members. The pediatrician is usually the first to evaluate the condition. This makes familiarity with its features, and its management, essential. This article covers some of the recent findings and advances in the field to help practitioners stay current on issues related to this skin disorder.

Identify recent findings in the pathogenesis and management of atopic dermatitis in children.

Understand the treatment options for various aspects of atopic dermatitis as it presents in children.

Summarize areas currently under study in the primary prevention of atopic dermatitis in the pediatric population.…

Wynnis L. Tom, MD, is Assistant Professor of Pediatrics and Medicine, Dermatology, University of California, San Diego, and Rady Children’s Hospital, San Diego, CA.

Dr. Tom has disclosed no relevant financial relationships.

Address correspondence to: Wynnis L. Tom, MD, fax: 858-966-4040; email: wtom@rchsd.org.

Posted Online: January 13, 2012

A topic dermatitis, often called “eczema,” is one of the most common chronic conditions affecting children (see Figure 1). The associated itch, inflammation, and sleep loss have a profound effect on the quality of life of the child, as well as on family members. The pediatrician is usually the first to evaluate the condition. This makes familiarity with its features, and its management, essential. This article covers some of the recent findings and advances in the field to help practitioners stay current on issues related to this skin disorder.

Infant with atopic dermatitis showing typical inflamed plaques and xerosis. Source: Tom W. Reprinted with permission.

Figure 1. Infant with atopic dermatitis showing typical inflamed plaques and xerosis. Source: Tom W. Reprinted with permission.

Defective Skin Barrier

The pathogenesis of atopic dermatitis (AD) is complex, but is now thought to stem from a genetically predisposed defective epidermal barrier that allows increased allergen, irritant, and microbial penetration; these ultimately elicit a dysregulated inflammatory response. The production of cytokines, recruitment of T-lymphocytes and other cells, and scratching in response to itch lead to further impairment of the skin barrier, ensuing in a vicious cycle.1,2

Multiple defects affecting both the structure and function of the epidermis are present in AD. These include a decrease in the quantity of ceramide lipids, an imbalance of protease enzymes over their inhibitors, and increased tran-sepidermal water loss.1,2 Genome-wide association and large-scale candidate gene studies have generated insight into some of the genes leading to skin barrier dysfunction. In particular, loss-of-function mutations in the filaggrin (FLG) gene have been a widely replicated major risk factor for AD. FLG is a structural protein involved in aggregating keratin filaments. These provide the template for assembly of the cornified envelope (the envelope that surrounds the outermost cells of the skin); its breakdown products play a role in the water-binding capacity of the stratum corneum. FLG mutations are associated with more severe AD, early onset of disease, enhanced systemic allergen sensitization, and an increased risk for asthma in those with a history of AD.3

However, there are certainly other factors involved in the pathogenesis of AD. Many with severe disease do not have FLG null mutations, and approximately 40% with null mutations in FLG do not have AD. Some of the other implicated factors include other members of the epidermal differentiation complex, and tight junction proteins in the stratum granulosum (eg, claudin), the layer directly below the stratum corneum.2,4 The genetics of atopic dermatitis and the influence on disease remain an evolving picture.

Emollients vs. Topical Barrier Repair Products

Proper skin care and treatment of xerosis are cornerstones of AD management. Mild, fragrance-free cleansers should be used and bubble baths avoided. Thicker emollients such as ointments and creams are better than lotions and should be used several times daily, particularly after bathing.

Besides traditional emollients, a newer class of topical products has been developed to address the defective skin barrier itself. Initial agents included pamitoylethanolamide cream, a 70% oil dispersed in 30% water hydrolipid cream, and a glycyrrhetinic acid-containing hydrolipid cream. These were followed by ceramide-based creams, including one with a 3:1:1 ratio of ceramide: cholesterol:free fatty acids that uses physiologic lipid components to optimize epidermal function and repair. There is evidence that these topicals can lessen the amount of topical corticosteroids (TCs) used, as well as help with itch and xerosis.5,6

The 3:1:1 ceramide:cholesterol:free fatty acids cream was tested in a randomized, investigator blind trial against fluticasone cream. The barrier repair agent was not as effective as the topical steroid in reducing disease severity in the first several weeks of use, but reached comparable effect by 4 weeks.6 However, these prescription barrier repair products are significantly more expensive than traditional emollient ointments and creams, plus there are few comparative data to demonstrate superiority.

One recent trial found equal efficacy among the glycyrrhetinic acid-containing hydrolipid cream, the 3:1:1 cer-amide:cholesterol:free fatty acids cream, and an over-the-counter (OTC) petroleum-based skin protectant moisturizer when used for 3 weeks in those with mild to moderate AD.7 In addition, these barrier therapies are approved under the FDA’s 510(k) registration as medical devices without active ingredients and have not had the same long-term efficacy and safety testing required of approved drugs. More recently, creams that contain ceramide and filaggrin breakdown products have been introduced to the OTC market. Their use shows improved hydration relative to not using any emollient, but they have not been compared with other OTC products.8 Thus, while barrier repair agents may be helpful adjuvant therapies to decrease AD symptoms, xerosis, and perhaps the need for topical anti-inflammatory medications, their role and benefit relative to traditional emollients remain unclear.

Anti-Inflammatory Use and Safety

The second major hallmark of AD is cutaneous inflammation. TCs remain the mainstay of therapy to control this aspect of disease. Prescribing methods vary greatly: with some using a short burst of mid- to high-potency agents to induce remission, followed by a quick tapering of potency; and others using the lowest potency thought to be needed, then adjusting upward if these fail. Newer formulations of TCs include nongreasy foams and hydrogels, which may be useful for hair-bearing sites such as the scalp. Topical calcineurin inhibitors (TCIs) are alternatives to TCs and are approved as second-line agents for the short-term and noncontinuous chronic treatment of moderate to severe AD in immunocompetent patients aged 2 years or older.9 Since 2006, they have carried a boxed warning stating that their long-term safety has not been established because rare post-market cases of malignancy (ie, skin cancer and lymphoma) have been reported with treatment.

Studies to address these concerns include one involving 293,253 patients, which found an increased risk for lymphoma that correlated with AD severity but not with TCI use.10 Interim analysis of an ongoing 10-year observational study at 4.3 years has also not found any evidence of increased malignancy risk with their use.11 Unlike topical steroids, TCIs do not carry a risk for skin atrophy, and therefore they can be helpful for sites of thinner skin (ie, face, eyelids, groin) or to decrease the use of topical steroids in those with recurrent disease.

The overall goals of AD therapy are: to obtain clearance/control of flares; to prolong the period until the next flare with a long-term maintenance phase; and to establish a rescue strategy in the event of disease relapse. Proactive therapy can be beneficial in the maintenance phase, in which a topical anti-inflammatory agent is used on a scheduled intermittent basis two to three times weekly rather than waiting until the disease recurs. Randomized controlled trials using TCs and TCIs in this manner noted a reduced risk of relapse, decreased number of exacerbations, and increased time to first recurrence without any adverse effects.12,13 Histologic and expression studies have found that non-lesional and previously involved but subsequently normal-appearing skin are not actually “normal,” but show some mild inflammatory changes and continued barrier defects.14,15 It is not unexpected that in some patients such sites could relapse relatively quickly; scheduled intermittent therapy may be appropriate for managing these cases.

Pruritus

Itch remains one of the most distressing features of AD and still lacks optimal therapy. Although widely used, there is little evidence that H1 antihistamines improve AD-associated pruritus. Sedating H1 blockers may be helpful at night due to their soporific effect. Other mediators of itch include cytokines, prostaglandins, proteases, and neuropeptides such as substance P, which binds to neurokinin receptor-1. A pilot study of an oral antagonist of this receptor found a reduction in itch in those with chronic pruritus and an atopic diathesis.16

Recent data have also shown upregulation of IL-31, a T-cell-derived cytokine, in animal models and in AD skin samples.17 The histamine H4 receptor, which is expressed on T cells, antigenpresenting cells, and keratinocytes, may also play a role in AD-associated itch.18 These are additional potential targets for the development of antipruritic therapy.

Environmental Factors

Although it is common to recommend limiting contact with potential triggers, such as astringents, harsh detergents, abrasive fabrics/wool, and excessive heat or low humidity in those with AD, these mainly stem from consensus and expert opinion, with few supportive studies. The role of aeroallergens, such as dust mites and animal dander, as triggers also remains unclear.9,19

Although commonly implicated by parents, foods are not necessarily causative of AD flares. Rather, those with AD are predisposed to have food allergy as a comorbid condition, but such allergies generally manifest on the skin as hives (urticaria) or angioedema. In 2010, the National Institute of Allergy and Infectious Diseases (NIAID) published guidelines stating that a positive specific IgE test or skin prick test alone does not constitute a food allergy. Instead, a reproducible adverse health effect must occur (ie, skin, gastrointestinal, or respiratory symptoms) with exposure. Regarding children with AD, testing is recommended for milk, egg, peanut, wheat, and soy only in those younger than 5 years of age with moderate to severe disease if they have either: persistent disease despite appropriate therapy; or a reliable history of an immediate reaction after ingestion of a specific food. If there is no documented or proven food allergy, it is not recommended to avoid potentially allergenic foods as a means of managing AD.20 Testing and dietary challenge or avoidance trials should be done under the supervision of an allergist.

Increasingly recognized in children, including those with worsening or recalcitrant AD, is the high prevalence of allergic contact dermatitis. Unlike urticaria, this is a delayed hypersensitivity reaction. The most common allergens in children include nickel, cobalt, neomycin/antibiotics, fragrance, and rubber chemicals.21 Diagnosis is made by patch testing, whereby suspected allergens are placed on unaffected skin for 24 to 48 hours. The reaction is noted at patch removal, and again at a later delayed reading. Patch testing should be considered in cases in which there is an unusual and atypical distribution of lesions for AD; if there is later onset of disease or new significant worsening; if there is no family history of atopy; if the disease is aggravated by topical medications or emollients; and in those not responding to standard therapies for AD.21,22

Cutaneous Immune System and Secondary Infections

Skin affected with AD is particularly prone to bacterial and viral infections. This is due to the defective physical barrier, combined with an immune response to microbes that is impaired on several levels. AD skin has decreased expression of antimicrobial peptides (eg, cathelicidin, beta-defensin), inadequate pathogen recognition by innate immune receptors, and diminished recruitment of cells such as neutrophils and natural killer cells to combat infectious agents after their entry.1,2

Exacerbation of AD related to colonization and infection by Staphylococcus aureus is well-recognized, and oral antibiotic use and occasional dilute bleach bath therapy (once to twice weekly) can be of benefit in those with repeated infection.23S. aureus may secrete exotoxins that act as superantigens to activate T lymphocytes and drive excessive inflammation. Of interest are data from several centers that suggest that children with AD may actually have lower rates of methicillin-resistant S. auerus (MRSA) skin infection than those without AD, but further affirmation is needed.24

Secondary infection by herpes simplex virus, called eczema herpeticum (EH, Figure 2, see page e2), tends to occur in those with more severe manifestations of AD, earlier age of disease onset, or with additional associated allergic disorders and/or high serum IgE levels. Recent studies have shown that those with a history of EH have additional defects relative to those who do not get secondary herpes infection, with further suppression of antimicrobial peptide production and even lower expression of skin barrier proteins and enzymes producing natural moisturizing factor.25,26

Eczema herpeticum is a secondary infection with the herpes simplex virus and can be severe, as seen in this 16-year-old patient. Typically, the lesions erode quickly and intact vesicles may not be seen. Source: Tom W. Reprinted with permission.

Figure 2. Eczema herpeticum is a secondary infection with the herpes simplex virus and can be severe, as seen in this 16-year-old patient. Typically, the lesions erode quickly and intact vesicles may not be seen. Source: Tom W. Reprinted with permission.

Prevention

Primary prevention of AD is highly desired, but little has shown consistent positive effect. Probiotic use in pregnant mothers and infants has yielded conflicting results, with dosing, timing, and the type of probiotic used varying greatly among studies. Maternal avoidance of cow’s milk, eggs, and peanuts during pregnancy does not appear to affect risk.

Studies assessing the association of breast-feeding and the development of AD have been limited by methodologic differences and flaws in study design and blinding; results have ranged from demonstration of a protective effect in those with a family history of atopy to suggestion of a higher risk for AD with longer duration of breast-feeding. There is a modest but inconsistent benefit with low-allergen maternal diets during lactation and with the use of hydrolyzed protein formulas compared with cow’s milk formulas. Soy formulas do not appear to be helpful.27,28 Currently, exclusive breast-feeding for at least 4 months is recommended for infants at high risk for developing AD, but delaying the introduction of solids (including possible allergenic foods) beyond the first 4 to 6 months of life is not advocated for any infant.9,29

More recently, focus has turned to skin barrier protection in the newborn period to prevent AD. An open-label, prospective study of at least daily use of OTC emollient and petrolatum in high-risk newborns found three of 20 (15%) developed disease during the follow-up period. The researchers said that similar high-risk cohorts have a 30% to 50% rate of AD by the age of 2 years, but their time of follow-up (ranging from 90 to 773 days) was not adequate to make comparison; additionally, the small sample size is limiting.30 Nevertheless, early barrier protection for the primary prevention of AD is an intriguing concept needing further investigation. Additional studies under way include a comparison of commonly used OTC emollients with topical application of natural/plant oils (eg, sunflower seed oil, coconut oil) for prevention.

Conclusion

Matching the pathophysiology, the management of AD is multimodal and must include improving the skin barrier, controlling inflammation, reducing itch, treating and preventing infections, and addressing and/or avoiding triggers. Figure 3 (see page e3) illustrates an approach to management of a child with AD. Much work is ongoing to understand better the factors at play and to improve therapeutic options, both for those affected as well as for those at risk for disease.

Management approach for atopic dermatitis. Source: Tom W. Reprinted with permission.

Figure 3. Management approach for atopic dermatitis. Source: Tom W. Reprinted with permission.

References

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  25. Hata TR, Kotol P, Boguniewicz M, et al. History of eczema herpeticum is associated with the inability to induce human β-defensin (HBD)-2, HBD-3 and cathelicidin in the skin of patients with atopic dermatitis. Br J Dermatol. 2010;163(3):659–661. doi:10.1111/j.1365-2133.2010.09892.x [CrossRef]
  26. Broccardo CJ, Mahaffey S, Schwarz J, et al. Comparative proteomic profiling of patients with atopic dermatitis based on history of eczema herpeticum infection and Staphylococcus aureus colonization. J Allergy Clin Immunol. 2011; 127(1):186–193, 193.e1–e11. doi:10.1016/j.jaci.2010.10.033 [CrossRef]
  27. Batchelor JM, Grindlay DJ, Williams HC. What’s new in atopic eczema? An analysis of systematic reviews published in 2008 and 2009. Clin Exp Dermatol. 2010; 35(8):823–827. doi:10.1111/j.1365-2230.2010.03901.x [CrossRef]
  28. Vandenplas Y. Infant formula with partial protein hydrolysates: evidence and remaining questions. J Pediatr Gastroenterol Nutr. 2010; 50(4):356–358.
  29. Filipiak B, Zutavern A, Koletzko S, et al. Solid food introduction in relation to eczema: results from a four-year prospective birth cohort study. J Pediatr. 2007; 151(4):352–358. doi:10.1016/j.jpeds.2007.05.018 [CrossRef]
  30. Simpson EL, Berry TM, Brown PA, Hanifin JM.A pilot study of emollient therapy for the primary prevention of atopic dermatitis. J Am Acad Dermatol. 2010; 63(4):587–593. doi:10.1016/j.jaad.2009.11.011 [CrossRef]

CME Educational Objectives

  1. Identify recent findings in the pathogenesis and management of atopic dermatitis in children.

  2. Understand the treatment options for various aspects of atopic dermatitis as it presents in children.

  3. Summarize areas currently under study in the primary prevention of atopic dermatitis in the pediatric population.

Authors

Wynnis L. Tom, MD, is Assistant Professor of Pediatrics and Medicine, Dermatology, University of California, San Diego, and Rady Children’s Hospital, San Diego, CA.

Dr. Tom has disclosed no relevant financial relationships.

Address correspondence to: Wynnis L. Tom, MD, fax: 858-966-4040; email: .wtom@rchsd.org

10.3928/00904481-20111209-06

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