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This is a clinician-written, evidence-based summary aligned to the USMLE Step 2 CK Content Outline. It is intended for medical students preparing for USMLE Step 2 CK. Management reflects current ACC/AHA, USPSTF, and APA guidelines. Always cross-reference with UpToDate, institutional protocols, and clinical judgment.
The Bottom Line
- Atopic dermatitis = chronic itchy eczema with xerosis and relapsing inflammation
- Infants: cheeks/extensor surfaces; children/adults: flexural areas such as antecubital and popliteal fossae
- Core treatment: daily emollients, trigger avoidance, topical corticosteroids for flares
- Face/folds: use low-potency steroids or topical calcineurin inhibitors to reduce atrophy risk
- Severe or refractory disease: phototherapy or systemic therapy such as dupilumab, tralokinumab, JAK inhibitors, or other specialist-directed options
Overview
Atopic dermatitis is a chronic inflammatory skin disease characterized by pruritus, xerosis, eczematous lesions, and barrier dysfunction. It is associated with personal or family history of atopy, including asthma and allergic rhinitis. Scratching perpetuates inflammation through the itch-scratch cycle. Diagnosis is clinical. Step 2 CK often tests distribution by age, first-line use of moisturizers and topical steroids, secondary infection, and eczema herpeticum as an emergency.
Epidemiology
Atopic dermatitis is common, affecting up to 10-20% of children and a smaller but substantial proportion of adults. It often begins before age 5. Risk factors include family history of atopy, filaggrin loss-of-function variants, urban environment, low humidity, irritant exposure, and food allergy in selected children. Disease severity varies from mild intermittent flexural eczema to severe diffuse disease with sleep disturbance, infection, and impaired quality of life.
Clinical Features
Symptoms
Pruritus is essential and often severe, worse at night
Dry sensitive skin with recurrent flares triggered by irritants, heat, sweating, stress, infections, or allergens
Sleep disturbance, irritability, impaired school/work functioning
Painful monomorphic vesicles, punched-out erosions, fever, or eye symptoms suggest eczema herpeticum
Honey-colored crusting, weeping, or rapidly worsening erythema suggests bacterial superinfection
Signs
Erythematous papules/plaques with excoriations and lichenification in chronic disease
Infants: cheeks, scalp, trunk, extensor surfaces; diaper area often spared
Children/adults: flexural surfaces, neck, wrists, ankles, hands
Xerosis, Dennie-Morgan infraorbital folds, hyperlinear palms, pityriasis alba
Diffuse erythroderma or systemic toxicity suggests severe flare, infection, or alternative diagnosis
Investigations
First-line
Clinical diagnosisBased on chronic relapsing pruritic dermatitis with typical morphology/distribution and atopic background
Assess severity and triggersExtent, sleep loss, infection, psychosocial burden, occupational irritants, topical treatment use, and steroid phobia
Second-line
Bacterial or viral testingCulture if recurrent impetiginization or MRSA concern; HSV PCR/culture if eczema herpeticum suspected
KOH prepUse when tinea corporis, tinea incognito, or candidiasis is in the differential
Patch testingConsider if refractory dermatitis, adult-onset disease, or distribution suggests allergic contact dermatitis
Specialist
Food allergy testingNot routine; consider only when immediate reproducible reactions or severe refractory childhood AD with suggestive history
BiopsyRarely needed unless diagnosis is uncertain, adult-onset atypical disease, cutaneous T-cell lymphoma concern, or treatment failure
Management
AAD Atopic Dermatitis Guidelines1
Skin-barrier care
- Daily liberal fragrance-free emollients are foundational, including immediately after bathing
- Short lukewarm baths/showers; avoid harsh soaps, fragrances, wool, and known irritants
- Wet-wrap therapy can help short-term in moderate-severe flares under guidance
2
Topical anti-inflammatory therapy
- Topical corticosteroids for flares: potency depends on age, body site, severity, and duration
- Low-potency steroid for face, eyelids, groin, and skin folds; avoid prolonged high-potency use due to atrophy and striae
- Topical calcineurin inhibitors (tacrolimus/pimecrolimus) for face/folds or steroid-sparing maintenance
- Topical crisaborole or ruxolitinib may be used in selected patients depending on age, severity, and access
- Proactive intermittent therapy to frequent flare sites can reduce relapses
3
Infection and severe disease
- Treat impetiginized eczema with appropriate anti-staphylococcal antibiotics when clear infection is present
- Eczema herpeticum: urgent systemic acyclovir/valacyclovir; ophthalmology if eye involvement
- Moderate-severe refractory AD: phototherapy or systemic therapy such as dupilumab/tralokinumab, JAK inhibitors, cyclosporine, methotrexate, azathioprine, or mycophenolate under specialist care
4
Patient education
- Explain itch-scratch cycle and safe steroid use to improve adherence
- Avoid routine elimination diets without clear allergy because nutritional harm can occur
- Manage sleep disturbance and psychosocial burden; consider comorbid asthma/allergic rhinitis
Complications
- Secondary bacterial infection: Staphylococcus aureus impetiginization with honey crusting
- Eczema herpeticum: Disseminated HSV with monomorphic vesicles/punched-out erosions; dermatologic emergency
- Lichenification: Chronic thickened skin from scratching
- Sleep and mental health effects: Poor sleep, anxiety, depression, impaired school/work performance
- Topical steroid adverse effects: Atrophy, striae, telangiectasia when excessive potency/duration used
USMLE Step 2 CK Exam Tips
- 1Atopic dermatitis must itch; no itch makes the diagnosis less likely
- 2Infant cheeks/extensors; older child/adult flexures = classic age-dependent distribution
- 3First-line chronic care = emollients; flare care = topical corticosteroids
- 4Face/folds need low-potency steroid or topical calcineurin inhibitor
- 5Eczema herpeticum = painful punched-out erosions + fever in eczema patient; treat with acyclovir urgently
- 6Honey-colored crusting = impetiginized eczema from S aureus
- 7Do not order broad food allergy panels for routine eczema without immediate food reaction history
- 8Flexural eczema vs extensor silvery plaques helps separate atopic dermatitis from psoriasis
practicetest your knowledge on atopic dermatitisApply what you've learnt with USMLE Step 2 CK-style questions from the iatroX Q-Bank — dermatology and beyond.
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