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

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  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.
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  8. Sargen MR et al. J Invest Dermatol. 2014;134(1):51–7.
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  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.
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  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.
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