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Atopic Dermatitis

Basics

  • Chronic, relapsing, inflammatory, intensely pruritic skin disease.
  • Early-onset cases often show allergen sensitization.
  • Variable clinical phenotypes indicating multifactorial pathophysiology.
  • Significant quality of life impact on patient and family.

Epidemiology

  • 45% of cases begin within first 6 months; 80-95% onset before age 5.
  • 50-66% remit spontaneously before adolescence.
  • Late-onset or relapse in adults mainly as hand eczema.
  • More common in darker pigmented individuals.
  • Familial aggregation: 60% risk if one parent affected, 80% if both; 80% concordance in monozygotic twins.
  • Prevalence ~20% in children, 10% in young adults, 2% in later adulthood.

Etiology and Pathophysiology

  • Systemic T-helper cell driven disorder.
  • Stratum corneum alteration β†’ increased transepidermal water loss β†’ barrier dysfunction.
  • Reduced epidermal adhesion due to genetic mutation (filaggrin gene - FLG) or immune dysregulation.
  • IL-31 upregulation mediates pruritus via cytokines and neuropeptides, not histamine.

Risk Factors

  • Itch-scratch cycle perpetuates inflammation.
  • Skin infections, emotional stress, irritating clothes/chemicals.
  • Climate extremes (hot/cold).
  • Food allergies (association unclear).
  • Tobacco smoke exposure.
  • High mineral content water exposure possibly exacerbates.
  • Family history of atopy, asthma, allergic rhinitis.

Commonly Associated Conditions

  • Food allergies.
  • Asthma and allergic rhinitis (atopic march).
  • Cutaneous and extracutaneous infections (URI, otitis media, UTI, cellulitis, erysipelas, zoster).
  • Hyper-IgE syndrome (Job syndrome).

Diagnosis

History

  • Chronic relapsing course.
  • Major symptoms: itching (54%), dryness/scaling (19.6%), inflamed skin (7.2%), skin pain (8.2%), sleep disturbance (11.4%).

Physical Exam

  • Lesion distribution:
  • Infants: face, trunk, extensor surfaces; diaper area spared.
  • Children: antecubital/popliteal fossae, wrists, ankles.

  • Adults: hands, feet, face, neck, upper chest, genitalia, flexor surfaces.

  • Lesion morphology:

  • Infants: erythema, papules, oozing, crusting vesicles.

  • Children/adults: lichenification, scaling from chronic scratching.

  • Associated signs: facial erythema, perioral pallor, Dennie-Morgan folds, dry skin/ichthyosis, palmar markings, pityriasis alba, keratosis pilaris.

Differential Diagnosis

  • Photosensitivity rashes
  • Contact dermatitis (especially facial)
  • Scabies
  • Seborrheic dermatitis (infants)
  • Psoriasis, lichen simplex chronicus (localized adult eczema)
  • Rare infantile conditions (histiocytosis X, Wiskott-Aldrich, ataxia-telangiectasia, ichthyosis vulgaris)

Diagnostic Tests

  • No definitive diagnostic test.
  • Serum IgE elevated in ~80%, not routinely required.
  • Eosinophilia correlates with severity.
  • SCORAD (Scoring Atopic Dermatitis) evaluates extent and symptoms.

Treatment

General Measures

  • Avoid irritants (wool, perfumes).
  • Minimize sweating.
  • Lukewarm baths; minimum twice weekly; post-bath emollients.
  • Use mild acidic (pH 5-6) hypoallergenic cleansers.
  • Humidify living spaces; avoid excessive water exposure.
  • Avoid alcohol-containing lotions.
  • Screen for coexisting contact dermatitis if resistant.

Pediatric Considerations

  • Potent fluorinated corticosteroids may cause striae, hypopigmentation, atrophy.

Medication

  • First line:
  • Frequent application of thick emollients (Eucerin, Vaseline) over moist skin ("soak and seal").
  • Topical corticosteroids:
    • Infants/children: short courses moderate potency (hydrocortisone valerate 0.2%, 0.5-1%).
    • Adults: higher potency corticosteroids sparingly; avoid face and folds.
  • Topical immunomodulators (tacrolimus, pimecrolimus) for children >2 years; may combine with steroids.

  • Antihistamines (hydroxyzine) limited benefit for itch.

  • Second line:

  • Crisaborole (PDE-4 inhibitor) twice daily topical ointment, FDA-approved β‰₯3 months age; expensive.
  • Plastic occlusion to improve absorption (not for face).
  • Topical doxepin 5% cream for itch.
  • Modified Goeckerman regimen (tar + UV light).

  • Treat secondary bacterial infection promptly.

  • Biologic therapy:

  • Dupilumab (IL-22, IL-17, IFN-Ξ³ pathway inhibitor), FDA-approved β‰₯6 months old, weekly injections, costly.

  • American Academy of Dermatology recommends against routine antibiotics without infection, oral/injectable steroids, and allergy testing unless indicated.

Issues for Referral

  • Ophthalmology for vernal conjunctivitis or prolonged periocular steroid use (cataract risk).
  • Dermatology for systemic immunotherapy (cyclosporine, azathioprine, methotrexate) in severe disease or quality of life impact.

Additional Therapies

  • Environmental allergen control: mite-proof bedding, HVAC filters.
  • Behavioral relaxation therapy to reduce scratching.
  • Bleach baths (1/2 cup 6% bleach per tub water, 5-10 min soak) - evidence limited.

Complementary & Alternative Medicine

  • Evening primrose oil (fatty acids) may reduce prostaglandin synthesis.
  • Probiotics may reduce severity and medication use.

Ongoing Care

  • Monitor for secondary bacterial/fungal infection; treat clinically evident infections especially Staphylococcus aureus.

Diet

  • Trial elimination diets to identify triggers.
  • Breastfeeding with maternal hypoallergenic diet may reduce infant severity.

Patient Education

  • Refer to American Academy of Dermatology and National Eczema Association resources.

Prognosis

  • Chronic condition improving with age; 90% pediatric resolution by puberty.
  • Localized eczema may persist in adults.

Complications

  • Cataracts (especially with steroids).
  • Skin infections, including eczema herpeticum (HSV infection causing severe illness).
  • Atrophy or striae from topical steroids, especially with occlusion or potent fluorinated steroids.

ICD10 Codes:
- L20.9 Atopic dermatitis, unspecified
- L20.89 Other atopic dermatitis
- L20.83 Infantile (acute) (chronic) eczema

Clinical Pearls:
- Early and proactive treatment reduces inflammation and complications.
- Use lowest potency steroid effective.
- Monitor for secondary infection.
- Frequent emollient use on moist skin is foundational therapy.