Dermatology Board Prep

Recognize the lesions, treat the rashes, refer the cancers. Daily ABFM practice grounded in AAD guidelines and primary care realities.

Dermatology contributes 5 to 7 percent of the ABFM Family Medicine boards. While smaller than cardiology or preventive care, dermatology questions are clinically rich and reward visual pattern recognition. The exam favors high-prevalence conditions you would actually see in a primary care clinic: acne, atopic dermatitis (eczema), psoriasis, contact dermatitis, common skin infections (cellulitis, impetigo, tinea), and skin cancer recognition. Dominant references include AAD (American Academy of Dermatology) clinical guidelines, the IDSA skin and soft tissue infection guidelines, and USPSTF skin cancer screening recommendations.

Skin cancer recognition is one of the highest-yield single topics. Three lesion types account for almost all primary care concern: basal cell carcinoma (pearly, telangiectatic, slow-growing), squamous cell carcinoma (scaly, hyperkeratotic, sometimes ulcerated), and melanoma (asymmetric, irregular border, color variation, diameter over 6 mm, evolving — the ABCDE criteria). Suspicious lesions warrant biopsy: shave biopsy is acceptable for clear basal or squamous cell, but melanoma suspicion requires full-thickness biopsy (excisional preferred, or punch biopsy) to assess Breslow depth. Never shave-biopsy a suspected melanoma — this is a tested error.

Acne management follows the 2024 AAD guidelines. Topical retinoids are foundational for almost all acne. Add benzoyl peroxide (reduces resistance development) for inflammatory components. Topical antibiotics (clindamycin) are appropriate as part of combination therapy, never as monotherapy due to resistance. Moderate inflammatory acne adds oral antibiotics (doxycycline first-line). Severe nodulocystic acne, refractory acne, or scarring acne warrants isotretinoin referral with iPLEDGE enrollment. Hormonal therapy (combined oral contraceptives, spironolactone) is effective in women with hormonal-pattern acne.

Atopic dermatitis (eczema) is treated with the basic eczema bundle: regular emollient use (the most evidence-supported intervention), trigger avoidance, topical corticosteroids during flares (low-potency for face and intertriginous areas, mid- to high-potency for body), and topical calcineurin inhibitors (tacrolimus, pimecrolimus) as steroid-sparing options. Severe refractory cases now have biologics like dupilumab as a referral option. Bleach baths and wet wraps help moderate cases.

Skin infections are a heavily tested practical topic. Cellulitis is treated empirically based on whether MRSA risk factors exist: cephalexin for non-purulent cellulitis without MRSA risk; trimethoprim-sulfamethoxazole or doxycycline (which cover MRSA but not strep) added or substituted if MRSA features (purulence, abscess, prior MRSA). Abscesses primarily require incision and drainage; antibiotics are added for surrounding cellulitis, immunocompromise, or large abscesses. Impetigo is treated with topical mupirocin for limited disease, oral antibiotics for extensive disease. Tinea responds to topical antifungals; oral terbinafine for tinea capitis or extensive infection.

High-yield dermatology topics

• Skin cancer recognition (ABCDE criteria). Asymmetry, Border irregularity, Color variation, Diameter over 6 mm, Evolving. Basal cell: pearly, telangiectatic, slow-growing, sun-exposed areas. Squamous cell: scaly, hyperkeratotic, sometimes ulcerated. Suspect melanoma in any pigmented lesion meeting ABCDE criteria — full-thickness biopsy required.
• Acne stepwise treatment (AAD 2024). Mild comedonal: topical retinoid plus benzoyl peroxide. Mild inflammatory: add topical antibiotic (clindamycin). Moderate: add oral antibiotic (doxycycline). Severe nodulocystic or scarring: isotretinoin referral. Women with hormonal pattern: spironolactone or combined oral contraceptive. Never use topical antibiotic alone.
• Atopic dermatitis management. Daily emollients (foundation of treatment). Topical corticosteroids during flares: low-potency for face, mid to high for body. Topical calcineurin inhibitors as steroid-sparing. Bleach baths for moderate cases. Wet wraps for severe flares. Dupilumab for severe refractory disease (referral).
• Cellulitis empirical antibiotics. Non-purulent cellulitis without MRSA risk: cephalexin or dicloxacillin (cover strep). Purulent cellulitis or MRSA risk factors (recent IV antibiotics, prior MRSA, IDU, severe disease): TMP-SMX or doxycycline. For abscess: incision and drainage is primary; antibiotics if surrounding cellulitis, immunocompromise, or systemic features.
• Tinea infections and antifungal selection. Topical azoles (clotrimazole, miconazole) or terbinafine for tinea corporis, cruris, pedis. Oral terbinafine for tinea capitis (in children, 4 to 6 weeks) and onychomycosis (6 weeks for fingernails, 12 weeks for toenails). Confirm onychomycosis with KOH or culture before treating.
• Psoriasis management. Mild plaque psoriasis: topical corticosteroids plus calcipotriene or tazarotene. Moderate to severe (over 5 to 10 percent BSA, scalp, palms/soles, genital): phototherapy or systemic therapy. Biologics (TNF inhibitors, IL-17, IL-23 inhibitors) for moderate-severe disease per AAD-NPF guidelines. Screen for psoriatic arthritis annually.
• Skin cancer screening (USPSTF). USPSTF Grade I (insufficient evidence) for routine clinical visual skin cancer screening in average-risk adults. Patient education on sun protection (Grade B) for fair-skinned adults age 6 months and older. Self-skin examination is reasonable for high-risk patients (significant sun exposure, family history, prior skin cancer, atypical nevi).
• Common pediatric skin conditions. Hand-foot-mouth disease (Coxsackie): vesicles on hands, feet, mouth, supportive care. Erythema infectiosum (fifth disease, parvovirus B19): "slapped cheek" then lacy rash, supportive care. Roseola (HHV-6): high fever then rash as fever breaks. Scabies: pruritus worse at night, burrows in webspaces, treat with permethrin 5 percent.

ABFM exam tips

For any pigmented lesion meeting ABCDE criteria, biopsy is the answer. "Watchful waiting" or "topical steroid trial" are wrong answers for suspected melanoma. Full-thickness biopsy (excisional preferred, deep punch acceptable) is required to assess Breslow depth.

Never shave-biopsy a suspected melanoma. Shave biopsy can transect a deep melanoma, miss invasive depth, and complicate staging. This is one of the most-tested errors in dermatology questions on the ABFM.

For acne, layer treatments by severity. Topical retinoid plus benzoyl peroxide is foundation. Add topical antibiotic (always with benzoyl peroxide). Add oral doxycycline for moderate inflammatory disease. Refer for isotretinoin in severe, scarring, or refractory disease. Avoid topical antibiotic monotherapy (resistance).

For cellulitis, MRSA risk drives antibiotic choice. Non-purulent without MRSA risk: cephalexin. Purulent or MRSA risk factors: TMP-SMX or doxycycline. Severe disease or systemic features: hospitalize and use IV antibiotics (vancomycin or linezolid for MRSA coverage).

For abscesses, I&D is the primary intervention. Antibiotics alone are not curative for established abscess. After I&D, antibiotics are added for surrounding cellulitis, immunocompromise, large abscesses (over 5 cm), or systemic features.

Recognize "scaly" vs "smooth" rash patterns. Eczema is itchy, scaly, often flexural, with dry skin. Psoriasis has well-demarcated plaques with silvery scale, often extensor. Tinea has central clearing with peripheral scale. Contact dermatitis has a clear distribution pattern. Pattern recognition is testable.

Common pitfalls

Do not use topical antibiotic monotherapy for acne. Resistance develops rapidly with single-agent topical antibiotic use. Always combine with benzoyl peroxide (which reduces resistance) or a retinoid. Clindamycin alone is inadequate and is a tested error.

Do not prescribe oral isotretinoin without iPLEDGE enrollment. All prescribers, pharmacies, and patients must be registered. Female patients require two negative pregnancy tests before starting and monthly thereafter, with two contraception methods. Liver enzymes, lipids, and pregnancy testing on schedule. This is a referral-level medication for primary care purposes.

Do not miss acanthosis nigricans as a marker for insulin resistance. Velvety, hyperpigmented skin in flexural areas (neck, axilla, groin) suggests insulin resistance and warrants metabolic workup (fasting glucose or A1c). Treating the skin alone misses the underlying disease.

Do not use systemic steroids for atopic dermatitis flares. Oral steroids cause rebound flares when tapered and can severely worsen long-term control. Use topical steroids appropriately and reserve systemic therapy (cyclosporine, methotrexate, dupilumab) for refractory cases — these are referral-level.

Do not miss necrotizing fasciitis. Pain out of proportion to exam, rapidly spreading erythema, systemic toxicity, crepitus, hemorrhagic bullae, or skin necrosis are emergency findings. Surgical consultation and broad-spectrum IV antibiotics (carbapenem plus clindamycin plus MRSA coverage) are urgent. This presents in ABFM vignettes as "the question that looks like cellulitis but is not."

Do not over-treat tinea versicolor with antifungals indefinitely. Hypopigmented or hyperpigmented patches caused by Malassezia respond to selenium sulfide shampoo, ketoconazole shampoo, or topical azoles. Pigmentation changes resolve over months after treatment. Recurrence is common; preventive monthly shampoo use is reasonable.

Do not treat seborrheic keratoses as concerning. "Stuck-on," waxy, well-demarcated brown lesions in older adults are benign seborrheic keratoses. They do not require biopsy unless atypical features are present. Patients sometimes worry about new lesions; reassurance is the answer.

Frequently asked questions

How much dermatology is on the ABFM?

Dermatology typically makes up 5 to 7 percent of the ABFM exam, or roughly 15 to 22 questions. Skin cancer recognition, acne, eczema, common skin infections, and rashes account for the majority. Visual pattern recognition is rewarded, and the questions assume you can recognize classic descriptions in words.

What is the right way to biopsy a suspected melanoma?

Excisional biopsy with narrow (1 to 3 mm) margins is preferred. Deep punch biopsy through the thickest area is acceptable when excisional is not feasible. Shave biopsy is contraindicated because it can transect the lesion and prevent accurate Breslow depth assessment. Refer to dermatology if you are uncertain about technique.

How do I treat cellulitis based on MRSA risk?

Non-purulent cellulitis without MRSA risk: cephalexin or dicloxacillin (cover Group A strep). Purulent cellulitis, abscess, or MRSA risk factors (recent IV antibiotics, prior MRSA, IDU, severe disease, healthcare exposure): TMP-SMX or doxycycline. Severe disease: hospitalize for IV vancomycin. Add MRSA coverage when uncertain in moderate disease.

When does acne need oral therapy?

Moderate inflammatory acne not responding to topicals warrants oral antibiotics (doxycycline 100 mg twice daily for 3 to 6 months). Severe nodulocystic acne, scarring acne, or refractory disease warrants isotretinoin referral. Hormonal-pattern acne in women may benefit from spironolactone or combined oral contraceptives.

What are the AAD recommendations for atopic dermatitis maintenance?

Daily emollient use is the cornerstone, applied twice daily and after bathing while skin is damp. Topical corticosteroids for flares (low-potency for face and intertriginous, mid- to high-potency for body). Topical calcineurin inhibitors as steroid-sparing maintenance. Bleach baths twice weekly for moderate cases. Identify and avoid triggers (irritants, allergens, stress).

Should I screen all adults for skin cancer?

Routine clinical visual skin cancer screening in asymptomatic adults is USPSTF Grade I (insufficient evidence). Patient counseling on sun protection (sunscreen, protective clothing, avoiding peak UV exposure) is Grade B for fair-skinned adults aged 6 months and older. High-risk patients (significant sun exposure, family history, prior skin cancer, atypical nevi) often have annual full-skin examinations.

How do I recognize necrotizing fasciitis on the boards?

Pain out of proportion to physical findings, rapidly progressive erythema, systemic toxicity (fever, hypotension, tachycardia), crepitus, hemorrhagic bullae, or skin necrosis. The LRINEC score helps risk-stratify. Treatment is emergency surgical debridement plus broad-spectrum IV antibiotics including MRSA and anaerobic coverage. Delay in surgery is the leading cause of death.