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Papulosquamous
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Trunk / extremities
Palms / soles
Skin folds / intertriginous
Scalp / face
Acute / self-limited
Chronic / persistent
Child / adolescent
Adult
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NO FILTER · 41 CANDIDATES · DON'T-MISS ALWAYS SHOWN
COMMON (20)
PITYRIASIS ROSEA-LIKE (5)
Pityriasis rosea
Herald patch, christmas-tree pattern on the trunk, collarette scale, self-limited course
Drug-induced pityriasis rosea-like eruption
More widespread, larger plaques, less collarette scale, no herald patch, often pruritic and may persist or progress; classic triggers include ACE inhibitors (captopril), NSAIDs, beta-blockers, hydrochlorothiazide, gold, terbinafine, omeprazole, isotretinoin, biologics (TNF and checkpoint inhibitors), COVID-19 mRNA vaccines
Tinea corporis
Single or few annular plaques with active raised edge and central clearing, scale at advancing border; KOH positive
Guttate psoriasis
Smaller, drop-shaped, more uniform plaques with silvery (not collarette) scale; preceded by streptococcal pharyngitis; involves extensor surfaces; no herald patch
Nummular eczema
Round coin-shaped plaques, exudative or crusted, intensely pruritic, not in christmas-tree pattern, often on extremities; lichenification with chronicity
LICHEN PLANUS AND LICHENOID (3)
Lichen planus
Shiny, flat-topped, polygonal, violaceous papules with Wickham striae; wrists, flexor forearms, dorsal hands, presacral area, lower legs and genitalia; mucous membranes often involved; mean age 50
Lichenoid drug eruption
More generalized and symmetric including the trunk, often sparing classic lichen planus sites; more eczematous, psoriasiform or pityriasis rosea-like; Wickham striae uncommon; hyperpigmentation very common; photodistribution common with hydrochlorothiazide and other photosensitizers; mucous membranes usually spared; mean age 65
Hypertrophic lichen planus
Pruritic, thick, hyperkeratotic plaques, especially on the legs, shins and dorsal feet; persistent; squamous cell carcinoma risk
PALMS AND SOLES (6)
Psoriasis (plaque)
Well-marginated plaques with scale or pustules; psoriasis lesions elsewhere including nails; positive family history; psoriatic arthritis
Atopic dermatitis
Personal or family history of atopy; distal fingers with subacute or chronic change; apron distribution on the palms
Dyshidrotic / keratotic hand eczema
Clusters of vesicles on palms and volar fingers; central palm; some view keratotic eczema as a psoriasis variant
Tinea pedis
Interdigital spaces plus lateral foot involvement; often symmetric, accompanied by onychomycosis; dorsal and lateral lesions have well-demarcated circinate borders; occasional vesicular variant
Allergic contact dermatitis (footwear)
Dermatitis of the dorsal feet and toes from an allergen in the shoe upper, or of the weightbearing soles from an allergen in the sole; common allergens dichromate, rubber accelerators, colophony, dyes, formaldehyde resins, and topical antibiotics such as bacitracin; sock or stocking dermatitis extends more proximally, most often from azo dyes
Juvenile plantar dermatosis
Glazed, erythematous, fissured skin on the weightbearing surfaces of the forefeet and great toes; children 3-14 years, resolves by puberty; related to friction from synthetic socks and shoes in atopic children; spares the interdigital spaces, which distinguishes it from tinea
SKIN FOLDS (6)
Irritant / frictional intertrigo
Ill-defined erythema and maceration; predisposing factors obesity, heat and humidity, hyperhidrosis, diabetes mellitus, poor hygiene; secondary infections common
Seborrheic dermatitis
Well-demarcated, pink to red, moist patches and plaques centered along the inguinal creases; involvement of scalp, face and ears
Inverse psoriasis
Well-demarcated, pink to red plaques, shiny with little scale in the folds, centered along the inguinal creases; psoriasiform plaques elsewhere (genitals, intergluteal cleft, scalp, elbows and knees, hands and feet); nail psoriasis with pitting and oil spots
Candidiasis (intertriginous)
Intense erythema with desquamation and satellite papules or pustules; often involves the scrotum as well as skin folds; predisposing factors occlusion, hyperhidrosis, diabetes mellitus, antibiotic or corticosteroid use, immunosuppression
Erythrasma
Pink-red to brown patches with fine scale; coral-red fluorescence with Wood's lamp illumination
Tinea cruris
Less often centered along the inguinal creases; expanding annular lesions with a scaly erythematous border that may contain pustules or vesicles; extension to inner thigh and buttock, usually spares the scrotum; coexisting tinea pedis or unguium very common
DON'T MISS (11) - ALWAYS SHOWN
PITYRIASIS ROSEA-LIKE (3)
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Secondary syphilis
Involves palms and soles (pityriasis rosea usually does not), copper or ham-colored lesions, mucous patches, condylomata lata, moth-eaten alopecia, lymphadenopathy, systemic symptoms
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Mycosis fungoides (patch stage)
Persistent patches in bathing-trunk distribution, atrophy, poikiloderma, slow evolution over years, fails to resolve over 6-8 weeks like pityriasis rosea
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Nutritional deficiency dermatitis (zinc, biotin)
Acral and periorificial distribution; associated systemic features
PITYRIASIS LICHENOIDES (1)
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Febrile ulceronecrotic Mucha-Habermann disease (FUMHD)
Hyperacute, fulminant onset over days; large coalescent ulceronecrotic plaques with hemorrhagic crust and eschar, widespread and can involve mucosa; high fever, malaise, arthralgias, lymphadenopathy, GI and CNS involvement, sepsis-like picture
LICHEN PLANUS AND LICHENOID (1)
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Lichen planopilaris
Follicular lichen planus; keratotic plugs surrounded by violaceous erythema, especially on the scalp but can affect any hair-bearing area; usually results in cicatricial alopecia
ERYTHRODERMIC (6)
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Sezary syndrome
Erythrodermic cutaneous T-cell lymphoma with more than 1000/uL circulating Sezary cells, lymphadenopathy, alopecia, ectropion and keratoderma
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DRESS / drug-induced hypersensitivity syndrome
Erythroderma with fever, eosinophilia, lymphadenopathy and organ involvement; classic 2-8 week onset after the culprit drug
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Crusted (Norwegian) scabies
Always consider in a nursing-home or immunosuppressed patient
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Adult T-cell leukemia/lymphoma
Erythroderma from HTLV-1 associated adult T-cell leukemia/lymphoma
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Graft-versus-host disease
Erythroderma, acute or chronic, after hematopoietic stem cell transplantation
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Paraneoplastic erythroderma from a solid tumor
Erythroderma driven by an underlying lung, gastrointestinal, prostate, breast or thyroid malignancy
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