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Acanthosis Nigricans
Appearance: hyper pigmented leathery plaque
Location: back of the neck, axilla, groin
Associated with: gastric, lung adenocarcinoma, Cushing Syndrome, PCOS
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Acanthosis Palmaris / Tripe Palms
Appearance: thickened velvety pattern of skin often gives a yellow hue to the skin
Location: palms and dorsal hands
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Accessory Tragus
Define: common, benign, congenital anomaly of the ear
Appearance: small, skin-colored nodule
Location: anterior to tragus
Tx: excise
Acne Keloidalis Nuchae
Appearance: flesh colored, dome shaped papules + pustules
Location: posterior scalp + neck
At risk: young darker tone male
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Acne Vulgaris
Etiology: folliculosebaceous unit is blocked, swollen, ruptures, and inflames the surrounding skin
Location: forehead, nose, chin, chest, upper back
Tx: tretinoin, adapalene, doxy, spironolactone
Acrochordons / Skin tags
Appearance: skin colored pedunculated, fleshy papules
Location: eyelids, neck, axillae, groin
Tx: snipping, LN, ED
Actinic Keratosis (AKs)
Appearance: pink/hyperpigmented thin scaly papules
Location: sun exposed areas
Tx: cryo
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African Trypanosomiasis
Etiology: T.b. rhodensiense, T.b. gambiense
Appearance:
- At site of Tsetse fly bite, chancre forms with enlarged lymph nodes
- 2-3 weeks later, a central necrotic eschar forms
- 6-8 weeks later, trypanids form (red patches, urticaria, targetoid lesions)
1/3
AL Amyloidosis
Etiology: accumulation of an immunoglobulin light chain (lambda > kappa) protein
Appearance: waxy skin with periorbital purpura (Raccoon eyes)
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Albinism
Etiology: mutation of TYR gene (oculocutaneous) = decreased tyrosine activity or defective tyrosine transportation
Inheritance: AR
Appearance: diffuse depigmentation
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Allergic Contact Dermatitis
Etiology: type IV hypersensitivity reaction to allergen (nickel, poison ivy, PCN, detergents)
Appearance: erythematous vesicular rash with edema
Alopecia Areata
Etiology: autoimmune condition
Appearance: hairless, smooth patches without scale, erythema, or inflammation
Test: positive hair test at periphery
Ass. conditions: autoimmune disorders, Down syndrome, atopy
Dermoscopy: exclamation point hairs
Tx: topical clobetasol solution, minoxidil, intralesional triamcinolone
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Angioedema
Appearance: swelling of dermis and SQ tissue
Location: face or portion of extremity
Sx: painful or burning, but not pruritic
Angiosarcoma
Etiology: 20% have history of radiation to head or neck
Appearance: blue or purple macular, sometimes raised or nodular; often become ulcerated or hemorrhagic
Location: face + scalp
Tx: complete resection with wide margins
Prog: 5 yr survival is ~35%
Angular Cheilitis
Appearance: erythematous fissuring, thin scales and crust
Location: corner of mouth
Ass. conditions: iron deficiency anemia, vitamin B deficiencies, protein malnutrition, chronic inflammatory diseases (IBD, Crohn Disease, Sjogren Syndrome)
1/8
Aphthous Ulcer / Canker Sore
Etiology: unknown antigen stimulates keratinocytes via increase pro-inflammatory cytokines
Appearance: round to oval ulcer with peripheral rim of erythema + yellowish adherent exudate centrally
Location: mucosa of lips, oral mucosa, tongue margins
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Aplasia cutis
Etiology: intrauterine trauma, vascular compromise, infection (HSV, VZV), meds (methimazole), Patau syndrome (on occiput)
Appearance: well-demarcated erosion or ulcer with loss of hair
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Arsenical keratosis
Define: development of thickened, wart-like growths on the skin due to chronic arsenic exposure
Appearance: multiple, small, yellowish, and horny (keratotic) papules or plaques
Location: palms + soles
At risk: farmers, well water use
Tx: cyro, ED, 5-FU, imiquimod, oral retinoids
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Arterial Ulcer
Etiology: peripheral artery disease (atherosclerotic stenosis)
Appearance: well defined punched out ulcer
Location: distal toes
Atopic Dermatitis / Eczema
Etiology: type 1 HS reaction associated with other atopic diseases; loss of function of FLG gene = mutation in filaggrin
Appearance: irregular border pink plaque with scale +/- lichenification
Location: flexural surfaces (adults) vs extensor surfaces (children)
Atopic Eruption of Pregnancy (AEP) / Prurigo of Pregnancy
Etiology: pregnancy causing cytokine imbalance
Appearance: hyper pigmented or erythematous papules
Prog: no increased risk to fetus
Tx: topical steroids
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