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- 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.
- 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.
- 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
- “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
- Allergic rhinitis
Commonly Associated Conditions
- Food sensitivity/allergy in many cases
- Allergic rhinitis
- Hyper-IgE syndrome (Job syndrome)
- Elevated IgE
- Recurrent pyodermas
- Decreased chemotaxis of mononuclear cells