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 is highly variable, suggesting multifactorial pathophysiology.
• May have significant effect on quality of life for patient and family-recurrent symptoms affect lifestyle and mental health.

Epidemiology

• 45% of all cases begin in the first 6 months of life with 95% onset prior to age 5 years.
• 50–66% of affected children will have a spontaneous remission before adolescence.
• Also, may have late-onset dermatitis in adults or relapse of childhood condition—primarily hand eczema
• Darker pigmented individuals are affected more often than lighter skinned individuals.
• 60% if one parent is affected; rises to 80% if both parents are affected

Incidence
On the rise over the past 3 decades in industrialized countries.

Prevalence
Approximately 13% of children and 7–10% of adults in the US (1)

Etiology and Pathophysiology

• Two main hypothesis: immunologic with unbalanced immune response and/or skin barrier dysfunction
• Alteration in stratum corneum results in transepidermal water loss and defect in barrier function.
• Epidermal adhesion is reduced either as a result of (i) genetic mutation resulting in altered epidermal proteins or (ii) 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 (FLG), which codes for a skin barrier protein
• 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). Studies of breastfeeding conveying decreased risk versus increased risk are mixed in conclusion (2)[C].
• Exposure to tobacco smoke
• Some evidence suggests that repeated exposure to “hard” water may exacerbate condition.
• Family history of atopy
  • Asthma
  • Allergic rhinitis

Commonly Associated Conditions

• Food sensitivity/allergy in many cases; strong association with asthma and allergic rhinitis
• Association with both cutaneous and extra-cutaneous infections: URI, OM, UTI, cellulitis, erysipelas, zoster, endocarditis, MRSA, MSSA, pharyngitis, and rarely sepsis (1)
• Hyper-IgE syndrome (Job syndrome)
  • AD
  • Elevated IgE
  • Recurrent pyodermas
  • Decreased chemotaxis of mononuclear cells