CAQ-Derm cheat sheet

Skin lesion description follows a fixed order: number, distribution (localized/generalized, symmetric, photodistributed, dermatomal), configuration (annular, linear, grouped, reticular), morphology, color, and secondary change (scale, crust, erosion, lichenification, atrophy).

Primary lesion vocabulary: macule <1 cm flat; patch ≥1 cm flat; papule <1 cm elevated; plaque ≥1 cm elevated with flat top; nodule deeper and palpable; vesicle <1 cm fluid-filled; bulla ≥1 cm; pustule pus-filled; wheal transient edema.

ABCDE melanoma criteria: Asymmetry, Border irregularity, Color variegation, Diameter >6 mm, Evolution (change). Sensitivity is imperfect; nodular and amelanotic melanomas may lack pigment and violate these rules.

Seven-point checklist for pigmented lesions scores major features (change in size, shape, color) as 2 points each and minor features (inflammation, crusting/bleeding, sensory change, diameter ≥7 mm) as 1 point; a total ≥3 warrants urgent referral.

Köbner phenomenon: isomorphic lesions appearing in traumatized skin, classically in psoriasis, lichen planus, vitiligo, and molluscum contagiosum.

Nikolsky sign (lateral pressure separates epidermis) is positive in pemphigus vulgaris and toxic epidermal necrolysis, and negative in bullous pemphigoid.

Dermoscopy of melanocytic lesions uses pattern analysis; a pigment network, irregular dots/globules, regression structures, and blue-white veil raise melanoma suspicion, while milia-like cysts and comedo openings favor seborrheic keratosis.

Patch testing is the gold standard for allergic contact dermatitis; readings are taken at 48-72 hours and again at 96-120 hours to capture delayed reactions.

Psoriasis: well-demarcated erythematous plaques with silvery scale on extensor surfaces and scalp; Auspitz sign (pinpoint bleeding on scale removal) and nail pitting/oil spots. First-line for limited disease is topical corticosteroid or vitamin D analog; phototherapy or systemic/biologic therapy for moderate-severe disease.

Atopic dermatitis: chronic relapsing pruritic eczematous lesions; flexural in adults, face/extensor in infants. Treatment is emollients plus topical corticosteroids, with calcineurin inhibitors as steroid-sparing options; dupilumab for moderate-severe refractory disease.

Contact dermatitis: sharply demarcated, often geometric or linear lesions confined to exposed skin; irritant is more common than allergic and does not require prior sensitization.

Pemphigus vulgaris: flaccid intraepidermal bullae, mucosal involvement, positive Nikolsky; IgG against desmoglein 1 and 3 on direct immunofluorescence with intercellular ('chicken wire') deposition.

Bullous pemphigoid: tense subepidermal bullae in older adults, negative Nikolsky; IgG against BP180/BP230 with linear deposition along the basement membrane zone.

Dermatitis herpetiformis: intensely pruritic grouped vesicles on extensor surfaces; granular IgA at dermal papillae on direct immunofluorescence; strongly associated with celiac disease and treated with dapsone plus gluten-free diet.

Erythema multiforme: target lesions with three zones, acrally distributed, usually triggered by herpes simplex virus; mucosal involvement defines EM major. Stevens-Johnson syndrome and toxic epidermal necrolysis are separate severe drug reactions classified by body surface area detachment (<10% SJS, >30% TEN).

Cellulitis: poorly demarcated, warm, tender, unilateral erythema with fever; Streptococcus pyogenes and Staphylococcus aureus are common pathogens. Erysipelas is a more superficial, sharply demarcated variant with raised borders, usually on the face or leg.

Acne vulgaris: follicular hyperkeratinization, sebum excess, Cutibacterium acnes colonization, and inflammation. Mild comedonal acne responds to topical retinoids; add benzoyl peroxide or topical antibiotic for inflammatory lesions; isotretinoin for severe nodulocystic or scarring disease.

Rosacea: centrofacial flushing, erythema, telangiectasia, and papulopustules without comedones; triggers include heat, sun, alcohol, and spicy food. Metronidazole or ivermectin topicals for papulopustular disease; oral doxycycline at subantimicrobial dose for anti-inflammatory effect.

Seborrheic dermatitis: greasy yellow scale on scalp, eyebrows, nasolabial folds, and chest; associated with Malassezia; treated with ketoconazole shampoo or topical azoles and low-potency corticosteroids.

Tinea corporis/pedis/cruris: annular scaly plaques with central clearing and active scaly border; potassium hydroxide preparation shows branching septate hyphae. Topical azoles or terbinafine for localized disease; oral terbinafine for extensive or hair/nail involvement.

Onychomycosis: distal and lateral subungual type is most common; confirm with KOH or fungal culture before prolonged oral therapy, since psoriasis and trauma can mimic it.

Onychocryptosis (ingrown toenail): lateral nail fold inflammation; risk factors include improper nail trimming, tight footwear, and hyperhidrosis; partial nail avulsion with matricectomy for recurrence.

Alopecia areata: well-circumscribed nonscarring patches with exclamation-mark hairs; associated with autoimmune disease and thyroid dysfunction; intralesional corticosteroids for localized disease.

Androgenetic alopecia: patterned hair loss driven by dihydrotestosterone at the follicle; minoxidil topical and finasteride (men) are first-line; finasteride is contraindicated in pregnancy and teratogenic.

Basal cell carcinoma: pearly papule with telangiectasia, rolled border, central ulceration; most common skin cancer, locally destructive, rarely metastasizes; treated with surgical excision, Mohs micrographic surgery for high-risk sites, or topical/oral hedgehog inhibitors in advanced disease.

Squamous cell carcinoma: hyperkeratotic or ulcerated nodule on sun-exposed skin; arises from actinic keratosis; risk of metastasis is higher than BCC, especially on lip, ear, and in immunosuppressed patients.

Actinic keratosis: rough, sandpaper-like erythematous macules on sun-damaged skin; treated with cryotherapy, topical 5-fluorouracil, imiquimod, or photodynamic therapy.

Melanoma: Breslow thickness in millimeters is the strongest predictor of survival; sentinel lymph node biopsy is considered for tumors ≥1 mm or thinner lesions with ulceration or high mitotic rate.

Cutaneous T-cell lymphoma (mycosis fungoides): patches, plaques, and tumors in sun-protected areas; Sezary syndrome adds erythroderma, lymphadenopathy, and circulating atypical T cells.

Kaposi sarcoma: HHV-8-associated vascular tumor with violaceous plaques/nodules; seen in HIV with low CD4 counts and in iatrogenic immunosuppression.

Dermatofibroma: firm, hyperpigmented nodule that dimples on lateral compression (Fitzpatrick sign); benign, no treatment needed unless symptomatic.

Seborrheic keratosis: 'stuck-on' verrucous plaque with horn cysts on dermoscopy; benign; can be removed with cryotherapy or curettage for cosmetic reasons. Sudden eruption of many lesions (Leser-Trélat sign) warrants evaluation for internal malignancy.

Urticaria: transient pruritic wheals lasting <24 hours per lesion; if individual lesions persist >24 hours or leave bruising, consider urticarial vasculitis and biopsy. Chronic spontaneous urticaria is treated with second-generation H1 antihistamines, up-dosed before adding omalizumab.

Angioedema with airway involvement is an emergency: intramuscular epinephrine, airway management, and antihistamines plus corticosteroids; hereditary angioedema responds to C1-inhibitor concentrate, icatibant, or lanadelumab, not to antihistamines.

Anaphylaxis: epinephrine 0.01 mg/kg intramuscularly (max 0.5 mg adult) into the anterolateral thigh, repeated every 5-15 minutes as needed; adjuncts are antihistamines and corticosteroids.

Stevens-Johnson syndrome/toxic epidermal necrolysis management: stop the culprit drug, transfer to a burn unit or ICU, fluids and wound care, and ophthalmologic evaluation; prophylactic antibiotics are not routinely recommended.

Erythema nodosum: tender red nodules on the anterior shins, no ulceration; associated with streptococcal infection, sarcoidosis, inflammatory bowel disease, and drugs including oral contraceptives; biopsy shows septal panniculitis.

Pityriasis rosea: herald patch followed by a 'Christmas tree' distribution of oval scaly plaques on the trunk; self-limited over 6-8 weeks; associated with HHV-6/7 reactivation.

Drug rash with eosinophilia and systemic symptoms (DRESS): fever, morbilliform eruption, facial edema, lymphadenopathy, eosinophilia, and internal organ involvement, typically 2-8 weeks after starting an aromatic anticonvulsant, allopurinol, or sulfonamide.

Morbilliform drug eruption: symmetric maculopapular rash starting on the trunk and spreading; most common cutaneous drug reaction; management is withdrawal of the culprit and symptomatic care.

Scabies: intense nocturnal pruritus with burrows in web spaces, wrists, and genitalia; treat with permethrin 5% cream or oral ivermectin, and treat all close contacts simultaneously; itch may persist 2-4 weeks after successful treatment.

Pediculosis capitis: nits attached to hair shafts and scalp excoriations; treat with permethrin 1% or dimethicone, repeat in 7-10 days; do not use flammable agents.

Herpes zoster: dermatomal vesicular eruption with pain; antiviral therapy (acyclovir, valacyclovir, famciclovir) is most effective within 72 hours of rash onset; ophthalmic involvement requires urgent ophthalmology referral.

Tinea versicolor: hypopigmented or hyperpigmented finely scaly macules on the trunk; Malassezia; KOH shows 'spaghetti and meatballs'; treat with selenium sulfide or ketoconazole, with recurrence common.

Verruca vulgaris: HPV-induced hyperkeratotic papule with loss of skin markings; destructive therapy with cryotherapy, salicylic acid, or immunotherapy; spontaneous resolution is common.

Molluscum contagiosum: umbilicated pearly papules caused by a poxvirus; common in children and in HIV with low CD4 counts; observation or curettage/cantharidin.

Erysipeloid: occupationally acquired (fish handlers, butchers) violaceous erythema of the hand caused by Erysipelothrix rhusiopathiae; treated with penicillin.

Cutaneous larva migrans: serpiginous pruritic track on the foot after contact with contaminated sand or soil; treated with ivermectin or albendazole.

Melanoma staging uses Breslow thickness, ulceration, mitotic rate, and sentinel node status; 5-year survival falls with increasing thickness and with nodal or distant metastasis.

Psoriasis is associated with metabolic syndrome, cardiovascular disease, and psoriatic arthritis; screen for joint symptoms and cardiovascular risk factors.

Atopic dermatitis is associated with asthma and allergic rhinitis (the atopic march); skin barrier dysfunction from filaggrin mutations is central to pathogenesis.

Vitiligo: depigmented macules with a sharply demarcated border; associated with thyroid disease, pernicious anemia, and Addison disease; screen for thyroid dysfunction.

Acanthosis nigricans: velvety hyperpigmented plaques on the neck and axillae; marker of insulin resistance; sudden extensive onset in a nonobese adult warrants evaluation for gastric adenocarcinoma.

Erythema migrans: expanding annular erythema ≥5 cm at a tick bite site, often with central clearing; treat with doxycycline for early Lyme disease.

Photosensitivity and porphyria cutanea tarda: blistering on sun-exposed dorsal hands, associated with hepatitis C, alcohol, and hemochromatosis; treat with phlebotomy or low-dose hydroxychloroquine.

Stevens-Johnson syndrome and toxic epidermal necrolysis are life-threatening; mortality correlates with the percentage of body surface area detached, and SCORTEN predicts in-hospital mortality.

Topical corticosteroid potency is classified by vasoconstrictor assay; class I (super-high) agents such as clobetasol are for short courses on thick skin, whereas low-potency agents are used on the face, groin, and in children.

Adverse effects of topical corticosteroids include skin atrophy, striae, telangiectasia, hypopigmentation, and tachyphylaxis; systemic absorption is greatest in thin skin and with occlusion.

Methotrexate for psoriasis is dosed weekly, not daily; supplement folic acid, monitor liver enzymes and blood counts, and avoid in pregnancy.

Isotretinoin is teratogenic: require two negative pregnancy tests before initiation, monthly pregnancy testing, and two forms of contraception; monitor lipids and transaminases.

Cyclosporine is nephrotoxic and causes hypertension; monitor blood pressure, creatinine, and drug levels, and avoid concurrent phototherapy because of increased skin cancer risk.

Biologic therapy for psoriasis (TNF inhibitors, IL-17 inhibitors, IL-23 inhibitors) requires screening for latent tuberculosis and hepatitis B before initiation.

Antihistamines are the mainstay of urticaria; first-generation agents cause sedation and anticholinergic effects, so second-generation agents are preferred for chronic disease.

Dapsone is used for dermatitis herpetiformis and leprosy; screen for G6PD deficiency before use and monitor for methemoglobinemia and hemolysis.

Skin biopsy techniques: punch biopsy for deep dermal and subcutaneous lesions, shave or saucerization for superficial lesions, excisional biopsy for suspected melanoma (full-thickness, with margins), and incisional biopsy for large tumors.

Direct immunofluorescence is the test of choice for autoimmune blistering disease; select perilesional normal skin, not the blister itself, and place it in Michel transport medium.

Potassium hydroxide (KOH) preparation: scrape scale from the active border; 10-20% KOH dissolves keratin; examine for hyphae, pseudohyphae, or budding yeast.

Wood's lamp: 365 nm ultraviolet light; coral-red fluorescence suggests erythrasma (Corynebacterium minutissimum), whereas tinea capitis caused by Microsporum can fluoresce blue-green.

Tzanck smear shows multinucleated giant cells in herpes simplex and varicella-zoster infection; it cannot differentiate HSV from VZV.

Patch testing indications: suspected allergic contact dermatitis, chronic hand eczema, and dermatitis unresponsive to treatment; use standardized allergen series and read at 48-72 and 96-120 hours.

Skin prick testing detects IgE-mediated immediate allergy; it has a high negative predictive value and is preferred over intradermal testing because of anaphylaxis risk.

The SCORTEN score for toxic epidermal necrolysis uses seven variables, including age, heart rate, malignancy, body surface area detached, urea, glucose, and bicarbonate, to predict mortality.

Sun protection: broad-spectrum sunscreen with SPF ≥30, reapplied every 2 hours and after swimming; protective clothing and avoiding peak UV hours reduce actinic damage.

Photoprotection matters in photosensitive disorders such as lupus, porphyria, and polymorphous light eruption; some drugs (tetracyclines, thiazides, amiodarone) cause photosensitivity.

Tanning beds are classified as carcinogenic and increase melanoma and squamous cell carcinoma risk; there is no safe threshold of UV exposure.

Vitamin D synthesis requires UVB; patients with minimal sun exposure should obtain vitamin D from diet or supplements rather than deliberate tanning.

Wound care basics: cleanse with saline, keep the wound moist with an appropriate dressing, and avoid topical antibiotics because of contact allergy risk; debridement for necrotic tissue.

Pressure ulcer prevention: repositioning, pressure-relieving surfaces, moisture management, and nutrition; stage by depth of tissue involvement, with unstageable ulcers covered by slough or eschar.

Venous stasis ulcer: medial malleolus location, shallow, with surrounding edema and hemosiderin staining; compression therapy is the mainstay when arterial disease is excluded.

Diabetic foot ulcer: pressure points on the plantar surface; offloading is essential; assess for neuropathy and peripheral arterial disease before debridement.

Pediatric atopic dermatitis: face and extensor involvement in infants, flexural in older children; use emollients liberally and low-potency topical corticosteroids; avoid food elimination diets without proven allergy.

Diaper dermatitis: irritant type affects convex surfaces sparing the creases; Candida adds satellite pustules in the creases; treat with barrier cream or topical nystatin.

Kawasaki disease: fever ≥5 days, conjunctivitis, mucositis, polymorphous rash, extremity changes, and cervical lymphadenopathy; risk of coronary aneurysm; treat with IVIG and aspirin.

Measles: morbilliform rash starting at the hairline and spreading downward, with Koplik spots and the three Cs (cough, coryza, conjunctivitis).

Staphylococcal scalded skin syndrome: widespread tender erythema with superficial peeling in children, caused by exfoliative toxin; Nikolsky positive; treat with antibiotics and supportive care.

Hand-foot-and-mouth disease: coxsackievirus; vesicles on the palms, soles, and oral mucosa; usually self-limited.

Hemangioma of infancy: grows in the first months, then involutes; beta-blockers (oral propranolol) are first-line for problematic lesions; watch for airway involvement with 'beard' distribution.

Child abuse recognition: patterned bruises, injuries in nonmobile infants, and injuries inconsistent with the developmental stage warrant reporting per local mandatory reporting requirements.

Skin aging: intrinsic aging causes fine wrinkles and laxity, while photoaging causes coarse wrinkles, dyspigmentation, and telangiectasia; topical retinoids and sun protection are evidence-based interventions.

Melasma: symmetric hyperpigmentation of the cheeks, forehead, and upper lip; associated with sun exposure, pregnancy, and hormonal therapy; treat with sun protection, topical hydroquinone, and tranexamic acid in selected cases.

Postinflammatory hyperpigmentation: occurs after inflammation, more common in darker skin phototypes; treat the underlying condition and use sun protection; avoid aggressive resurfacing.

Keloid: scar extending beyond the original wound margin; more common in darker skin and on the chest and earlobes; treat with intralesional corticosteroids, silicone, or excision with adjuvant therapy.

Hypertrophic scar: remains within the wound boundary; often improves over time; pressure therapy and silicone gel are first-line.

Alopecia: nonscarring types include androgenetic, telogen effluvium, and alopecia areata; scarring types include discoid lupus and lichen planopilaris, which require biopsy and urgent treatment to prevent permanent loss.

Telogen effluvium: diffuse shedding 2-3 months after a trigger such as illness, childbirth, or severe stress; self-limited; check ferritin and thyroid function.

Aging skin barrier: reduced lipid content and slower turnover increase irritant contact dermatitis risk; use gentle cleansers and emollients.

Sexually transmitted infection skin findings: primary syphilis chancre (painless, indurated ulcer with clean base), secondary syphilis (copper-red maculopapular rash on palms and soles, condylomata lata), and tertiary gummas; serology confirms.

Condyloma acuminatum: HPV 6 and 11 cause anogenital warts; HPV 16 and 18 carry the highest oncogenic risk; treat with cryotherapy, podophyllotoxin, or imiquimod.

Herpes simplex: grouped vesicles on an erythematous base; PCR is the preferred diagnostic test; suppressive therapy reduces recurrence.

Chancroid: painful, tender ulcer with ragged edges and suppurative inguinal lymphadenopathy; caused by Haemophilus ducreyi.

Molluscum contagiosum in adults can be sexually transmitted; lesions are umbilicated papules.

HIV-associated skin disease: Kaposi sarcoma, severe seborrheic dermatitis, oral hairy leukoplakia, and eosinophilic folliculitis occur with advanced immunosuppression.

Syphilis in pregnancy can cause congenital syphilis; screen at the first prenatal visit and treat with penicillin; desensitize if penicillin allergy.

Gonococcal and chlamydial infection may present with mucopurulent discharge or be asymptomatic; test all exposed contacts and treat empirically per guidelines.

Ethnic skin considerations: keloids, postinflammatory hyperpigmentation, and traction alopecia are more common; avoid high-potency corticosteroids on the face and intertriginous areas.

Central centrifugal cicatricial alopecia: scarring hair loss starting at the crown, common in women of African descent; associated with traction hairstyles; biopsy confirms and early treatment prevents progression.

Vitiligo treatment: topical corticosteroids or calcineurin inhibitors for limited disease, narrowband UVB for widespread disease, and camouflage; depigmentation is reserved for extensive disease.

Acanthosis nigricans and skin tags are markers of insulin resistance; address the underlying metabolic condition.

Hidradenitis suppurativa: recurrent painful nodules and abscesses in intertriginous areas (axillae, groin, inframammary); associated with smoking and obesity; treat with antibiotics, hormonal therapy, or biologics (adalimumab).

Pruritus in chronic kidney disease: generalized, worse at night; treat with emollients, gabapentin, or UVB phototherapy.

Pruritus in cholestasis: associated with jaundice; treat with cholestyramine, rifampin, or naltrexone.

Generalized pruritus without a rash in an older adult warrants evaluation for systemic disease, including thyroid disease, diabetes, renal or hepatic disease, and lymphoma.

Nail anatomy: the nail plate is produced by the matrix; the lunula is the visible distal matrix; the cuticle seals the proximal nail fold.

Beau lines: transverse depressions from temporary interruption of matrix activity after severe illness, chemotherapy, or trauma; grow out over months.

Onycholysis: separation of the nail plate from the bed; causes include psoriasis, onychomycosis, trauma, and hyperthyroidism.

Splinter hemorrhages: longitudinal hemorrhages under the nail plate; associated with trauma and endocarditis; nonspecific.

Pitting: punctate depressions in the nail plate; classic in psoriasis and alopecia areata.

Melanonychia: longitudinal pigmented band; Hutchinson sign (pigment extending onto the cuticle) raises concern for subungual melanoma and warrants biopsy.

Paronychia: acute (bacterial, usually Staphylococcus) versus chronic (irritant or Candida); treat acute with drainage and antibiotics; chronic with avoidance of irritants and topical steroid or antifungal.

Subungual hematoma: painful dark nail after trauma; trephination relieves pressure; larger hematomas may require nail removal.

Burns: estimate depth (superficial partial, deep partial, full thickness) and total body surface area using the rule of nines; parkland formula guides fluid resuscitation in the first 24 hours.

Superficial partial-thickness burn: painful, blistered, blanches; heals in 1-2 weeks; deep partial-thickness: less painful, mottled, heals with scarring.

Full-thickness burn: white or charred, insensate, leathery; requires excision and grafting.

Chemical burns: irrigate copiously with water; exceptions include dry lime (brush off first) and hydrofluoric acid (calcium gluconate).

Electrical burns: risk of cardiac arrhythmia and deep tissue injury; obtain ECG and monitor for rhabdomyolysis.

Frostbite: rapid rewarming in 37-39°C water; avoid rubbing; tPA for severe cases; watch for compartment syndrome.

Sunburn: erythema and pain 2-6 hours after exposure; treat with cool compresses, NSAIDs, and emollients; prevention with sunscreen is key.

Burn infection: signs include increased pain, discoloration, and systemic symptoms; wound cultures guide antibiotics; early excision reduces risk.

Lupus: acute cutaneous lupus (malar rash), subacute cutaneous lupus (annular or papulosquamous photodistributed lesions), and chronic cutaneous lupus (discoid plaques with scarring); biopsy and direct immunofluorescence (lupus band test) support diagnosis.

Dermatomyositis: heliotrope rash, Gottron papules, and proximal muscle weakness; associated with internal malignancy; screen with age-appropriate cancer screening.

Systemic sclerosis: sclerodactyly, Raynaud phenomenon, and nailfold capillary changes; CREST syndrome includes calcinosis, Raynaud, esophageal dysmotility, sclerodactyly, and telangiectasia.

Morphea: localized scleroderma with indurated plaques; no systemic involvement; treat with topical corticosteroids or phototherapy.

Sarcoidosis: erythema nodosum, lupus pernio, and maculopapular lesions; biopsy shows noncaseating granulomas.

Amyloidosis: waxy papules and purpura (pinch purpura) from dermal deposits; biopsy with Congo red stain shows apple-green birefringence under polarized light.

Mastocytosis: urticaria pigmentosa with Darier sign (wheal on rubbing); measure serum tryptase and screen for systemic involvement.

Sweet syndrome: tender erythematous plaques with fever and neutrophilia; associated with malignancy and drugs; responds to systemic corticosteroids.

Skin cancer screening: total-body skin examination for high-risk patients (fair skin, multiple nevi, family history, immunosuppression, prior skin cancer); document lesion size and location.

Dermoscopic follow-up: serial digital dermoscopy improves detection of early melanoma in patients with many atypical nevi.

Sun-protective behaviors and sunscreen use reduce actinic keratosis and squamous cell carcinoma risk.

HPV vaccination reduces anogenital warts and HPV-related cancers, including cervical and some oropharyngeal cancers.

Smoking cessation reduces hidradenitis suppurativa severity and improves wound healing.

Obesity is associated with psoriasis severity and hidradenitis suppurativa; weight management improves disease control.

Occupational skin disease prevention: identify and eliminate contact allergens and irritants, use protective equipment, and perform surveillance.

Patient education on chronic skin disease: adherence to topical therapy is often poor; simplify regimens and demonstrate application; address steroid phobia.

Dermatitis artefacta: self-induced lesions with bizarre shapes and sharp borders, often in areas accessible to the hands; the patient denies responsibility; approach nonjudgmentally.

Delusional parasitosis: fixed belief of infestation with excoriations and 'matchbox sign' (bringing specimens); treat with antipsychotics such as pimozide or risperidone.

Body dysmorphic disorder: preoccupation with an imagined skin defect; cosmetic procedures often worsen the condition; refer for psychiatric evaluation.

Trichotillomania: irregular patches of hair loss with broken hairs of varying lengths; treat with habit reversal therapy and SSRIs.

Neurotic excoriations: linear erosions and scars from picking; treat with SSRIs and habit reversal.

Psychosocial impact of psoriasis and acne: screen for depression and suicidal ideation, particularly with isotretinoin therapy.

Stress and skin: stress worsens psoriasis, atopic dermatitis, and urticaria; behavioral therapy may help.

Psychotropic drugs can cause skin reactions: lithium causes acne and psoriasis flares; SSRIs can cause sweating and bruising.

Eczema herpeticum: widespread vesicular eruption in a patient with atopic dermatitis, caused by HSV; a medical emergency requiring systemic antiviral therapy.

Cellulitis versus stasis dermatitis: bilateral leg erythema favors stasis dermatitis; cellulitis is usually unilateral and painful.

Necrotizing fasciitis: rapidly progressive pain out of proportion to findings, crepitus, and systemic toxicity; requires urgent surgical debridement and broad-spectrum antibiotics.

Toxic shock syndrome: fever, rash, hypotension, and multiorgan involvement; associated with staphylococcal or streptococcal toxins; remove the source and give antibiotics.

Erythroderma: generalized erythema with scaling involving >90% of body surface area; causes include psoriasis, drug reaction, and cutaneous T-cell lymphoma; risk of hypothermia, dehydration, and heart failure.

Stevens-Johnson syndrome: mucosal involvement plus <10% body surface area detachment; ophthalmologic and urologic evaluation are essential.

Purpura fulminans: disseminated intravascular coagulation with purpuric lesions in sepsis; treat the underlying infection and consider protein C replacement.

Rocky Mountain spotted fever: petechial rash starting on the wrists and ankles and spreading centrally; treat with doxycycline empirically, especially in children.

Leprosy (Hansen disease): hypopigmented anesthetic patches; caused by Mycobacterium leprae; diagnosis with skin slit smear or biopsy; treat with multidrug therapy (rifampin, dapsone, clofazimine).

Cutaneous tuberculosis: lupus vulgaris with apple-jelly nodules on diascopy; confirm with biopsy and culture.

Leishmaniasis: painless ulcer with raised border after sandfly bite; diagnose with Giemsa-stained smear; treat with liposomal amphotericin or pentavalent antimonials.

Tinea nigra: brown-black macule on the palm caused by Hortaea werneckii; treat with topical antifungal.

Chromoblastomycosis: verrucous nodules with 'copper penny' bodies on histology; caused by dematiaceous fungi; treat with itraconazole or excision.

Mycetoma: chronic swelling with sinus tracts and grains; caused by fungi or bacteria; requires prolonged antimicrobial therapy and sometimes surgery.

Ecthyma: deeper ulcerated form of impetigo with a thick crust; treat with systemic antibiotics.

Impetigo: honey-colored crusts; nonbullous type is usually streptococcal or staphylococcal; bullous type is staphylococcal toxin-mediated; treat with topical mupirocin for limited disease or oral antibiotics for extensive disease.

Wound healing phases: hemostasis, inflammation, proliferation, and remodeling; chronic wounds stall in the inflammatory phase.

Suture selection: absorbable sutures for deep and mucosal layers; nonabsorbable for skin surface; remove facial sutures in 5-7 days and trunk/extremity sutures in 10-14 days.

Local anesthesia: lidocaine with epinephrine prolongs duration and reduces bleeding; avoid epinephrine in digits or areas with end-arterial supply per traditional teaching, though evidence is limited.

Cryotherapy: liquid nitrogen for warts, actinic keratosis, and seborrheic keratosis; risks include hypopigmentation and scarring, especially in darker skin.

Electrosurgery and curettage: used for seborrheic keratosis and warts; ensure adequate hemostasis and proper specimen handling.

Mohs micrographic surgery: indicated for high-risk basal and squamous cell carcinoma and some melanomas; offers the highest cure rate with tissue conservation.

Surgical margins: basal cell carcinoma 4 mm for low-risk lesions; squamous cell carcinoma 4-6 mm; melanoma margins depend on Breslow thickness.

Postoperative care: keep the wound clean and moist, avoid sun exposure during healing, and counsel on scar management.

Hyperhidrosis: excessive sweating beyond thermoregulatory needs; focal (palmar, plantar, axillary) or generalized; treat with topical aluminum chloride, iontophoresis, botulinum toxin, or sympathectomy.

Bromhidrosis: unpleasant body odor from apocrine gland secretions and bacterial breakdown; treat with antibacterial cleansers and antiperspirants.

Vitiligo versus pityriasis alba: vitiligo is completely depigmented with a sharp border; pityriasis alba has ill-defined hypopigmentation with fine scale, common in children.

Tinea versicolor versus vitiligo: tinea versicolor has fine scale and KOH-positive hyphae; vitiligo has no scale.

Melasma versus postinflammatory hyperpigmentation: melasma is symmetric and photodistributed; PIH follows a preceding inflammatory lesion.

Hirsutism: excess terminal hair in a male pattern in women; evaluate for polycystic ovary syndrome and adrenal causes; treat with combined oral contraceptives or antiandrogens.

Hypertrichosis: excess hair growth in a nonandrogen-dependent pattern; may be drug-induced (minoxidil, cyclosporine) or paraneoplastic.

Skin tags: benign fibroepithelial polyps; associated with insulin resistance and obesity; remove for cosmetic reasons.

Psoriasis severity: body surface area <5% is mild, 5-10% moderate, and >10% severe; the Dermatology Life Quality Index captures impact on quality of life.

Atopic dermatitis severity: use the Eczema Area and Severity Index (EASI) or the SCORAD index; pruritus and sleep disturbance are key patient-reported outcomes.

Acne severity: count inflammatory and noninflammatory lesions; assess scarring and psychological impact; the Global Acne Grading System is commonly used.

Hidradenitis suppurativa staging: Hurley stage I (abscesses without sinus tracts), stage II (recurrent abscesses with sinus tracts and scarring), and stage III (diffuse involvement with multiple interconnected tracts).

Melanoma Breslow thickness: ≤1.0 mm, 1.01-2.0 mm, 2.01-4.0 mm, and >4.0 mm define T categories; ulceration and mitotic rate refine staging.

Alopecia severity: the Severity of Alopecia Tool (SALT) scores scalp hair loss; >50% loss may warrant systemic therapy.

Urticaria activity score: the UAS7 records wheals and itch daily over 7 days; a score ≥16 indicates severe disease.

Patient-reported outcomes: DLQI ≥10 indicates significant impairment; use it to justify systemic therapy and to monitor response.

Contact dermatitis history: ask about occupation, hobbies, cosmetics, and new products; the distribution often suggests the allergen (e.g., eyelid dermatitis from nail polish).

Atopic dermatitis history: ask about personal and family history of atopy, triggers, sleep disturbance, and response to prior therapy.

Psoriasis history: ask about joint pain, nail changes, and triggers such as streptococcal infection and medications (lithium, beta-blockers, antimalarials).

Hair loss history: ask about shedding patterns, styling practices, systemic illness, and medications; perform a hair pull test and examine the scalp for scarring.

Pigmented lesion history: ask about change in size, shape, color, bleeding, and itching; document with photography.

Drug eruption history: record all medications started in the preceding 8 weeks, including over-the-counter drugs and supplements.

Sexual history: ask sensitively about risk factors for STIs; screen for syphilis and HIV when indicated.

Occupational history: identify exposures to chemicals, irritants, and allergens; report occupational skin disease as required by local regulations.

Basal cell carcinoma subtypes: nodular, superficial, morpheaform, and pigmented; morpheaform is more aggressive and requires wider margins.

Squamous cell carcinoma variants: keratoacanthoma (rapid growth with central keratin plug), Bowen disease (in situ), and spindle cell carcinoma; high-risk features include depth >2 mm, perineural invasion, and immunosuppression.

Melanoma subtypes: superficial spreading (most common), nodular (fastest growing), lentigo maligna (sun-damaged elderly), and acral lentiginous (palms, soles, nail beds).

Merkel cell carcinoma: rapidly growing violaceous nodule in older adults; associated with Merkel cell polyomavirus; high metastatic potential.

Dermatofibrosarcoma protuberans: locally aggressive, rarely metastasizes; characterized by a t(17;22) translocation; treated with Mohs or wide excision.

Atypical fibroxanthoma: sun-exposed head and neck in older adults; diagnosis of exclusion; usually benign behavior.

Angiosarcoma: violaceous bruising-like lesion on the scalp or face of older adults, or post-radiation; poor prognosis.

Cutaneous B-cell lymphoma: violaceous nodules on the trunk or head; biopsy with immunohistochemistry and molecular studies.

Pruritus treatment: emollients, cool compresses, and avoidance of irritants; topical corticosteroids for inflammatory causes; antihistamines for histamine-mediated itch; gabapentin or pregabalin for neuropathic itch.

Pain management in skin disease: NSAIDs for mild pain; gabapentin or pregabalin for neuropathic pain; opioids for severe pain in conditions such as hidradenitis suppurativa.

Wound infection signs: increasing pain, erythema, warmth, purulent drainage, and systemic symptoms; obtain cultures and treat with antibiotics.

Antibiotic stewardship: use narrow-spectrum agents when possible; avoid topical antibiotics for simple wounds because of contact allergy risk.

Wound debridement: sharp, enzymatic, autolytic, or mechanical; remove necrotic tissue to promote healing.

Compression therapy: indicated for venous ulcers and lymphedema; contraindicated in uncompensated heart failure and severe arterial disease.

Nutrition in wound healing: protein, vitamin C, and zinc are essential; screen for malnutrition in patients with chronic wounds.

Prevention of pressure ulcers: risk assessment tools, repositioning, and support surfaces; document skin assessments.

Vitiligo pathogenesis: autoimmune destruction of melanocytes; associated with thyroid disease, pernicious anemia, and Addison disease; screen for thyroid dysfunction.

Melasma pathogenesis: melanocyte stimulation by UV, hormones, and visible light; treatment includes sun protection, hydroquinone, and tranexamic acid.

Postinflammatory hyperpigmentation pathogenesis: melanin deposition after inflammation; more common in darker skin; treat the underlying condition and use sun protection.

Acne pathogenesis: follicular hyperkeratinization, sebum production, C. acnes colonization, and inflammation; treat each component.

Rosacea pathogenesis: innate immune dysregulation, neurovascular instability, and Demodex mites; triggers include heat, sun, and spicy food.

Hidradenitis suppurativa pathogenesis: follicular occlusion, inflammation, and bacterial colonization; associated with smoking and obesity.

Psoriasis pathogenesis: IL-23/Th17 axis; biologics targeting IL-17 and IL-23 are highly effective.

Atopic dermatitis pathogenesis: skin barrier dysfunction (filaggrin), immune dysregulation (Th2), and microbial colonization (S. aureus).

Melanoma ABCDE: Asymmetry, Border irregularity, Color variegation, Diameter >6 mm, Evolution; sensitivity is imperfect for nodular and amelanotic melanoma.

Psoriasis Auspitz sign: pinpoint bleeding on removal of scale; indicates epidermal hyperproliferation.

Nikolsky sign: lateral pressure separates epidermis; positive in pemphigus vulgaris and toxic epidermal necrolysis.

Darier sign: wheal on rubbing a lesion; positive in urticaria pigmentosa (mastocytosis).

Fitzpatrick sign: dimpling on lateral compression; suggestive of dermatofibroma.

Koebner phenomenon: isomorphic lesions in traumatized skin; seen in psoriasis, lichen planus, vitiligo, and molluscum.

Hutchinson sign: pigment extending onto the cuticle; raises concern for subungual melanoma.

Leser-Trélat sign: sudden eruption of multiple seborrheic keratoses; warrants evaluation for internal malignancy.

Lichen planus: pruritic, purple, polygonal, planar papules with Wickham striae; mucosal involvement; associated with hepatitis C; treat with topical corticosteroids.

Pityriasis rosea: herald patch followed by a 'Christmas tree' distribution; self-limited; associated with HHV-6/7.

Erythema multiforme: target lesions with three zones; triggered by HSV; mucosal involvement defines EM major.

Urticaria: transient pruritic wheals lasting <24 hours; chronic spontaneous urticaria treated with second-generation antihistamines, up-dosed before omalizumab.

Erythema nodosum: tender red nodules on the anterior shins; septal panniculitis; associated with streptococcal infection, sarcoidosis, IBD, and drugs.

Vitiligo: depigmented macules with a sharp border; associated with thyroid disease and pernicious anemia.

Melasma: symmetric hyperpigmentation of the cheeks and forehead; associated with sun exposure, pregnancy, and hormonal therapy.

Acanthosis nigricans: velvety hyperpigmented plaques on the neck and axillae; marker of insulin resistance; sudden extensive onset warrants evaluation for gastric adenocarcinoma.