Diagnostic Criteria for Atopic Dermatitis
The diagnosis of atopic dermatitis is primarily clinical and should be based on essential criteria including pruritus, characteristic eczematous lesions with age-specific distribution patterns, and a chronic or relapsing course. 1
Essential Diagnostic Criteria
The American Academy of Dermatology recommends the following diagnostic approach:
Required Features:
- Pruritus (itching)
- Eczematous skin lesions that are:
- Acute: characterized by erythema, exudation, papules
- Chronic: characterized by lichenification, excoriations
- Age-specific distribution patterns
Age-Specific Distribution Patterns:
Infants (0-2 years):
- Face, scalp, and extensor surfaces of extremities
- Notable sparing of the diaper area
- Duration >2 months for diagnosis 1
Children (2-12 years):
- Flexural surfaces (antecubital and popliteal fossae)
- Neck, wrists, ankles
- Duration >6 months for diagnosis 1
Adolescents and Adults:
- Predominantly flexural surfaces
- Face and neck involvement
- Hand dermatitis common
- Duration >6 months for diagnosis 1
Chronicity Requirement:
- Chronic or relapsing course:
2 months in infants
6 months in children and adults 1
Supporting Features
While not required for diagnosis, these features strengthen the diagnostic certainty:
- Personal or family history of atopic diseases (asthma, allergic rhinitis)
- Xerosis (dry skin)
- Early age of onset
- Facial pallor or erythema
- Pityriasis alba (hypopigmented patches)
- Hyperlinear palms
- Keratosis pilaris
- Ichthyosis
- Periorbital darkening
- Periauricular fissures
- Increased susceptibility to skin infections 1, 2
Differential Diagnosis
The following conditions should be considered and ruled out:
- Seborrheic dermatitis (especially in infants)
- Contact dermatitis
- Scabies
- Psoriasis
- Nutritional deficiencies
- Immunodeficiency disorders
- Cutaneous T-cell lymphoma (in adults) 1
Key Distinguishing Features
- AD typically spares groin and axillary regions, while seborrheic dermatitis affects these areas 1
- AD is intensely pruritic, while seborrheic dermatitis is typically not 1
- Lichenification is a hallmark of chronic AD, indicating persistent inflammation and repeated scratching 2
Biomarkers and Laboratory Testing
- No specific biomarkers are recommended for routine diagnosis or severity assessment 1
- Elevated IgE levels are present in approximately 80% of patients but are not required for diagnosis 1
- Monitoring IgE levels is not recommended for routine assessment of disease severity 1
- Skin biopsy or other tests (KOH preparation, patch testing) may occasionally be helpful to rule out other conditions but are not routinely required 1
Severity Assessment
For clinical practice, a simplified approach to severity assessment is recommended:
- Mild: Limited areas of dry skin, infrequent itching, minimal impact on daily activities/sleep
- Moderate: Multiple areas of dry skin, frequent itching, moderate impact on daily activities/sleep
- Severe: Widespread areas of dry skin, persistent itching, significant impact on daily activities/sleep
- Very severe: Widespread areas with persistent eczema, continuous itching, severe limitation of daily activities/sleep 1
Common Pitfalls in Diagnosis
- Overreliance on laboratory tests for diagnosis
- Failure to recognize age-specific distribution patterns
- Not considering the chronicity requirement (>2 months in infants, >6 months in older children/adults)
- Overlooking the importance of pruritus as an essential feature
- Misdiagnosing seborrheic dermatitis in infants as AD (check diaper area involvement)
Clinical Pearls
- The diagnosis remains clinical; no laboratory test can definitively diagnose AD 1
- Lichenification indicates chronic disease and may require more potent treatments 2
- When therapy fails, reconsider the diagnosis and evaluate for complicating factors such as infection or contact dermatitis 1
- Formal severity scales (SCORAD, EASI) are valuable for research but not necessary for routine clinical practice 1
The diagnostic approach should focus on identifying the essential clinical features while recognizing that AD has diverse presentations based on age, chronicity, and individual factors.