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Atopic Dermatitis

Learning objectives

By the end of this chapter, participants will be able to:

  • describe how atopic dermatitis contributes to the ‘atopic march’ in patients predisposed to allergy
  • recall the importance of an early and accurate diagnoses of atopic dermatitis in infants and children.

Atopic dermatitis

  • Atopic dermatitis, a type of eczema, is a chronic inflammatory skin disease that affects up to 20% of children and 3% of adults worldwide.1
  • It is hypothesised that patients who develop atopic dermatitis have a genetic predisposition to a defective skin barrier2 and that additional damage inflicted by environmental factors can increase the risk of allergen penetration.3
  • Atopic dermatitis often begins in early childhood and can be the initial step of the ‘atopic march’ in several patients.1
  • The atopic march describes the gradual manifestation of other allergy-related diseases such as food allergies, allergic rhinitis and asthma in atopic individuals.1,4

Common triggers of atopic dermatitis

  • Patients are genetically predisposed to atopic dermatitis.
  • This may be through acquired mutations in proteins responsible for the maintenance of the skin barrier function.2,5 For example, the loss-of-function variants of filaggrin, a protein involved in epidermal differentiation and the formation of the skin barrier, has been shown to strongly predispose patients to atopic dermatitis.2,5
  • However, exogenous factors such as hormones,6,7 climate8 and infections9 can trigger flares or further exacerbate the disease.
  • Another common trigger is allergy. The most common allergens involved in atopic dermatitis are:

Clinical symptoms and features of atopic dermatitis

How should a GP carry out a physical examination for atopic dermatitis?

Why is a correct diagnosis important?

  • Atopic dermatitis is prevalent and the most common inflammatory skin condition in children and often begins in early infancy – incorrect or misdiagnosis of atopic dermatitis can lead to unnecessary elimination diets which may have a significant impact on the growth and physical development of the child.19
  • To distinguish atopic dermatitis from seborrheic dermatitis and other skin conditions that can mimic atopic dermatitis20 – this is particularly important in infants where physical examination cannot be used to discriminate between atopic and seborrheic dermatitis.
  • Patients and their guardians can often experience a lower quality of life, increased psychological and social burdens,21 which can be improved with effective therapeutic strategies.
  • Infants with eczema are more likely to develop IgE-mediated food allergy than infants without22 – an ongoing study is currently investigating whether prophylactic treatment in these patients can prevent food allergies developing.23

A diagnostic workflow for determining allergic triggers in atopic dermatitis15,24

  • General diagnosis of atopic dermatitis requires a thorough medical history and a physical examination of the entire skin organ.
  • Potential triggers that can exacerbate or cause atopic dermatitis to flare should be investigated if the patient’s history indicates any IgE-mediated sensitisation.
  • Both skin prick tests and specific IgE blood tests are recommended to support diagnosis of allergy-triggered atopic dermatitis. However, skin prick tests may be contraindicated in patient’s with widespread atopic dermatitis.
  • Due to increased risk of patients with atopic dermatitis developing other atopic diseases, patients must also be examined for allergic rhinitis and asthma.

 

 

What diagnostic approach is expert-recommended for atopic dermatitis?

Diagnostic tests for atopic dermatitis

Key factors a clinician should consider when managing patients with atopic dermatitis:

  • In patients with moderate-to-severe atopic dermatitis, atopic dermatitis is frequently associated with food allergies.26
    • Therefore, skin prick tests and specific IgE blood tests can be used to determine the patient’s sensitisation to the food allergen but the ultimate ‘gold standard’ test to confirm a food allergy is an oral food challenge test.27
  • Patients with atopic dermatitis have often elevated total IgE antibody levels and can exhibit polysensitisation to several allergens.28
    • This makes interpretation of diagnostic tests challenging, as patients can show sensitisation to multiple allergens that are clinically irrelevant.
  • Skin prick tests may be unsuitable for patients with atopic dermatitis.
    • Specific IgE blood tests are preferable over skin prick tests in patients who have severe eczematous lesions and are using oral anti-histamine medications at the time of testing.25

Component-resolved diagnostics in atopic dermatitis

The use of component-resolved diagnostics has been studied within diagnoses of atopic dermatitis. For example:

  • The component Gal d 1 found in egg whites was shown to be the superior component for differentiating asymptomatic sensitisation from egg allergy in a population of children with moderate-to-severe atopic dermatitis.29
  • Component-resolved diagnostics was used in conjunction with medical histories to select a personalised pharmacological therapy for two polysensitised patients with severe atopic dermatitis. This allowed patients to reintroduce foods they had previously eliminated from their diet whilst controlling their symptoms.30
  • The component Der p 11, an allergen found in house dust mites, was identified as a major allergen for patients suffering with atopic dermatitis but only a minor allergen for patients suffering with respiratory forms of the allergy.31

Several factors need to be considered when using component-resolved diagnostics in patients with atopic dermatitis. For example:

  • Careful selection of components is especially important for patients with atopic dermatitis – polysensitisation can lead to several positive tests making it more difficult to interpret the test results.
  • Sensitisation to an allergen component does not causally suggest that the patient is allergic the component’s source – a medical history should always be used to interpret these results.32

Summary

  • The symptoms of atopic dermatitis are common to many other skin conditions; incorrect or misdiagnosis of atopic dermatitis can lead to inappropriate intervention, e.g. elimination diets, which can have a detrimental impact on child development.
  • Specific IgE blood tests are preferable to skin prick tests in patients who have severe eczematous lesions and are using oral antihistamines medications at the time of testing.
  • Patients with atopic dermatitis often have elevated total IgE antibody levels and can exhibit polysensitisation to several allergens – therefore, careful interpretation is essential.

References

  1. Nutten S. Ann Nutr Metab. 2015;66(suppl 1):8–16.
  2. Palmer CAN et al. Nature Genetics. 2006;38(4):441–6.
  3. Cork MJ et al. J Allergy Clin Immunol. 2006;118(1):3–21.
  4. Spergel JM, Paller AS. J Allergy Clin Immunol. 2003;112(6):S118–27.
  5. Weidinger S et al. J Allergy Clin Immunol. 2006;118(1):214–9.
  6. Cho S et al. Ann Dermatol. 2010;22(2):180–5.
  7. Lin T-K et al. Int J Mol Sci. 2017;18(10):2131.
  8. Sargen MR et al. J Invest Dermatol. 2014;134(1):51–7.
  9. Kong HH et al. Genome Res. 2012;22(5):850–9.
  10. Werfel T et al. Allergy. 2007;62(7):723–8.
  11. Werfel T, Kapp A. Allergy. 1998;53(8):731–9.
  12. Schuttelaar MLA et al. Allergy. 2009;64(12):1758–65.
  13. Teplitsky V et al. Int J Dermatol. 2008;47(8):790–5.
  14. Fölster-Holst R at el. Clinic Cos Invest Dermatol. 2015;8:539–48.
  15. Eichenfield et al. J Am Acad Dermatol. 2014;70(2):338–51.
  16. Ong PY, Leung DYM. Clinic Rev Allerg Immunol. 2016;51(3):329–37.
  17. Ramirez FD et al. JAMA Pediatr. 2019;173(5):e190025.
  18. Thyssen JP et al. Allergy. 2018;73(1):214–20.
  19. David TJ et al. Archives of Disease in Childhood. 1984;59(4):323–5.
  20. Siegfried EC, Hebert AA. J Clin Med. 2015;4(5):884–917.
  21. Lifschitz C. Ann Nutr Metab. 2015;66(suppl 1):34–40.
  22. Martin PE. Clin Exp Allergy. 2015;45(1):255–64.
  23. Yamamoto‑Hanada K et al. Clin Transl Allergy. 2018;8(47):1–11.
  24. Werfel T et al. J Dtsch Dermatol Ges. 2016;14(1):92–105.
  25. Appropriate use of Allergy Testing in primary care. Best test. 2011:1–12.
  26. Dhar S, Srinivas SM. Indian J Dermatol. 2016;61(6):645–8.
  27. Bergmann MM. J Allergy Clin Immunol: In Practice. 2013;1(1):22–8.
  28. Broeks SA, Brand PLP. Acta Pædiatrica: 2017;106(3):485–8.
  29. Gray CL et al. Pediatric Allergy and Immunology. 2016;27(7):709–15.
  30. Fedenko et al. Pediatric Allergy and Immunology. 2016;27(letter to editor):645–659.
  31. Banerjee S et al. J Invest Dermatol. 2015;135(1):102–109.
  32. Portnoy JM. Missouri Medicine. 2011;108(5):339–43.
 
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This independent educational activity is supported by funding from Thermo Fisher Scientific. PCM Scientific is the medical education company acting as scientific secretariat and organiser for this programme. The activity is run independently of the financial supporter and all content is created by the faculty. No funder has had input into the content of the activity.
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