Dermatology confusion pairs
17 Dermatology topics students commonly mix up on Step 1, each with the fastest separator, a side-by-side comparison, and a free practice question.
- Eczema vs Psoriasis and seborrheic dermatitisEczema is itchy flexural atopy; psoriasis is extensor silvery plaques; seborrheic dermatitis is greasy scale in sebum-rich areas.Video
- Irritant contact dermatitis vs Allergic contact dermatitisIrritant is direct toxic barrier damage with burning; allergic is delayed type IV pruritic vesicular dermatitis after sensitization.
- Pemphigus vulgaris vs Bullous pemphigoid and dermatitis herpetiformisPemphigus is flaccid mucosal intraepidermal anti-desmoglein; pemphigoid is tense subepidermal hemidesmosome; dermatitis herpetiformis is…
- Erythema multiforme vs SJS and TENEM is target lesions with limited detachment; SJS is severe mucosal disease with under 10% BSA detachment; TEN is over 30% BSA detachment.Video
- Lichen planus vs Lichen sclerosusLichen planus is purple pruritic polygonal papules with Wickham striae; lichen sclerosus is white atrophic vulvar sclerosis with SCC risk.
- Acne vulgaris vs Rosacea and folliculitisAcne has comedones; rosacea has flushing/telangiectasia without comedones; folliculitis is follicle-centered pustules.
- Cellulitis vs Erysipelas and necrotizing fasciitisCellulitis is poorly demarcated deeper infection; erysipelas is raised sharply demarcated superficial infection; nec fasc is toxic…
- Impetigo vs Herpes and eczema herpeticumImpetigo is honey-crusted bacterial erosion; herpes is grouped vesicles; eczema herpeticum is disseminated punched-out HSV in atopic skin.
- Melanoma vs BCC, SCC, and actinic keratosisMelanoma is ABCDE pigmented melanocyte malignancy; BCC is pearly telangiectatic; SCC is scaly keratinizing; actinic keratosis is rough…
- Superficial spreading melanoma vs Nodular, lentigo maligna, and acral lentiginous melanomaSuperficial spreading is common radial trunk/leg; nodular is early vertical nodule; lentigo maligna is older sun-damaged face; acral is…
- Seborrheic keratosis vs Actinic keratosis and solar lentigoSeborrheic keratosis is stuck-on waxy; actinic keratosis is rough premalignant scale; solar lentigo is flat sun macule.
- Vitiligo vs Albinism and tinea versicolorVitiligo is acquired autoimmune depigmentation; albinism is congenital melanin synthesis defect; tinea versicolor is scaly Malassezia…
- Pityriasis rosea vs Secondary syphilis and tinea corporisPityriasis rosea is herald patch and Christmas tree; secondary syphilis hits palms/soles; tinea corporis is annular KOH-positive ringworm.
- Bullous pemphigoid vs Pemphigus vulgarisPemphigoid is tense subepidermal hemidesmosome disease; pemphigus is flaccid mucosal anti-desmoglein intraepidermal disease.Video
- NF1 cafe-au-lait macules vs McCune-Albright and tuberous sclerosis skin findingsNF1 is cafe-au-lait plus neurofibromas/Lisch; McCune-Albright is cafe-au-lait plus fibrous dysplasia/endocrine; tuberous sclerosis is…
- Tinea capitis vs Alopecia areata and trichotillomaniaTinea capitis is scaly fungal alopecia; alopecia areata is smooth autoimmune patches; trichotillomania is irregular broken hairs of…
- Kaposi sarcoma vs Bacillary angiomatosisKaposi is HHV-8 spindle-cell vascular tumor; bacillary angiomatosis is Bartonella vascular infection with silver-staining organisms.