5-Minute Clinical Consult

Dermatitis, Atopic

Dermatitis, Atopic is a topic covered in the 5-Minute Clinical Consult.

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Basics

Description

  • A chronic, relapsing, pruritic eczematous condition affecting characteristic sites
  • Early onset cases have coexisting allergen sensitization more often than late onset.
  • Clinical phenotypical presentation highly variable, suggesting multifactorial pathophysiology.

Epidemiology

  • 45% of all cases begin in the first 6 months of life with 95% onset prior to age 5 years.
  • 70% of affected children will have a spontaneous remission before adolescence.
  • Incidence on the rise for the past 3 decades in industrialized countries; overall, affects ~15% of children at some time (United States).
  • Also, may have late-onset dermatitis in adults or relapse of childhood condition—primarily hand eczema
  • Asians and blacks affected more often than whites
  • 60% if one parent affected; rises to 80% if both parents affected

Etiology and Pathophysiology

  • Two main hypothesis: immunologic with unbalanced immune response and/or skin barrier dysfunction (1)
  • Alteration in stratum corneum results in transepidermal water loss and defect in barrier function.
  • Epidermal adhesion is reduced either as a result of (a) genetic mutation resulting in altered epidermal proteins or (b) defect in immune regulation causing an altered inflammatory response.
  • Interleukin-31 (IL-31) upregulation is thought to be a major factor in pruritus mediated by cytokines and neuropeptides rather than histamine excess.

Genetics
  • Recent discovery of association between atopic dermatitis (AD) and mutation in the filaggrin gene (on chromosome 1), which codes for a skin barrier protein (2)
  • Both epidermal and immune coding likely involved

Risk Factors

  • “Itch–scratch cycle” (stimulates histamine release)
  • Skin infections
  • Emotional stress
  • Irritating clothes and chemicals
  • Excessively hot or cold climate
  • Food allergy in children (in some cases)
  • Exposure to tobacco smoke
  • Family history of atopy
    • Asthma
    • Allergic rhinitis

Commonly Associated Conditions

  • Food sensitivity/allergy in many cases
  • Asthma
  • Allergic rhinitis
  • Hyper-IgE syndrome (Job syndrome)
    • AD
    • Elevated IgE
    • Recurrent pyodermas
    • Decreased chemotaxis of mononuclear cells

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