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*USMLE* > Dermatology + STDs > Flashcards

Dermatology + STDs Flashcards

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USMLE® Step 1 flashcards
1
Q

actinic keratoses

s/s, histo + association

A

scaly, red, sandpapery lesions in sun-exposed areas

hyperkeratosis, parakeratosis + atypical keratinocytes

precursor to invasive SCC

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2
Q

basal cell carcinoma

description, histo, progno

A

sun-exposed areas; low metastatic potential

pearly papules with central depression or ulceration (#1 skin cancer)

nests of basaloid cells and peripheral palisading of nuclei

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3
Q

dermatofibroma

what are they? where are they + how do they look?

A

“superficial benign fibrous histiocytomas”; benign fibroblast proliferation

usually on legs, as solitary nodules

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4
Q

Kaposi sarcoma

association, appearance

A

HHV-8 in HIV patient

palpable macules, plaques + nodules; dark brown to violet

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5
Q

3 types of acne vulgaris + their characteristics

A

comedonal - closed or open comedones on forehead, nose + chin

inflammatory - small red papulse + pustules

nodular - large, painful nodules; sinus tracts + scarring

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6
Q

acne vulgaris pathogenesis

4 elements

A

hyperkeratinization - with pilosebaceous follicle obstruction

sebaceous gland enlargement - w/ increased sebum

Cutibacterium acnes - metabolizes sebum + releases inflammatory FFAs

follicular inflammation + rupture

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7
Q

acne vulgaris risk factors (5)

A

androgens - puberty, PCOS

mechanical - excess scrubbing, tight clothes

skin/hair products - oil is comedogenic

excess heat

obesity

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8
Q

Atopic Dermatitis

pathogenesis? clinical s/s? labs?

A

FILAGGRIN and other epidermal barrier protein defects > increased Ag exposure + hypersensitivity (assoc. with asthma, allergic rhinitis + family history)

intense pruritus
INFANTS - red, crusted lesions extensors + face/scalp/trunk (not diaper area)
ADULTS/KIDS - flexural eczema + lichenification

high IgE and eosinophilia

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9
Q

derma signs in ulcerative colitis (2)

A

pyoderma gangrenosum - ulcerative rash

erythema nodosum - painful raised red nodules

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10
Q

Langerhans cell histiocytosis

presentation? s/s? tx?

A

dendritic cell disorder > severe refractory red/ulcerative rash on SCALP, TRUNK, GROIN

infancy or early childhood

flares and resolves without intervention

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11
Q

1 prognostic factor + scales

Melanoma

A

1 progno = “Breslow depth” - distance from epidermal granular cell layer to the deepest visible melanoma cells

“Clark levels”
1 - only into stratum spinosum; 2 - thru basal layer + BM; 3 - well into papillary dermis; 4 - well into reticular dermis; 5 - into subcutaneous fat

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12
Q

Lentigo maligna

what is it? who has it?

histo? progno?

A

common pigmented lesions in ELDERLY; sometimes considered “melanoma in-situ” (atypical melanocytes along basilar layer just above BM)

MULTINUCLEATED GIANT MELANOCYTES are characteristic on histo

if it develops into “lentigo maligna melanoma” progno is similar to other melanomas of same stage

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13
Q

Heliotrope rash

how does it look, where is it, and what’s it assoc. with?

A

red/violet edematous eruption on UPPER EYELIDS and PERIORBITAL SKIN

dermatomyositis

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14
Q

Dermatomyositis

muscle biopsy, associations

A

PERIMYSIAL leukocytes, patchy ischemia/necrosis, and PERIFASCICULAR atrophy/fibrosis

can occur alone or as paraneoplasia to ADENOCARCINOMAS (more likely if pt develops dermatomyositis after 50)

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15
Q

Pemphigus Vulgaris

auto-Abs, sites, signs, type of WBC

A

anti-DESMOSOME antibody (desmoglein 1 and 3) deposit INTRAepidermally with EOSINOPHILIC infiltrate

weak, painful flaccid bullae on skin AND MUCOSA (mucosa rare in bullous pemphigoid)

ASBOE-HANSEN positive - bullae spread laterally when pressure is applied

NIKOLSKY positive - new blisters form with gentle traction/rubbing (negative in bullous pemphigoid)

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16
Q

Bullous Pemphigoid

auto-Abs, sites + signs

A

anti-HEMIDESMOSOME antibody (basement membrane) deposit SUBepidermally

Nikolsky NEGATIVE - new blisters do NOT form with rubbing

ASBOE-HANSEN positive - bullae spread laterally

only skin, no mucosa lesions

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17
Q

Skin lesion differential

Bartonella henselae vs. Mycobacterium marinum vs. Blastomyces dermatitidis

A

Bartonella - bacillary angiomatosis in immunocompromised; purple tender nodules; bleed if squeezed

M. marinum - wounds inoculated with contaminated water; solitary papule or nodule, eventually ulcer + scarring; granulomatous inflamm. on histo

Blastomyces - verrucous lesions, irregular borders; culture for dx; histo shows granulomas

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18
Q

Wound contracture

when does it happen + via what cells/enzymes

A

healing by second intention (large wound with irregular borders)

MMPs encourage MYOFIBROBLAST (fibroblasts with ACTIN) accumulation around wound edge; excess MMPs can result in contracture

(MMPs made by fibroblasts, macros, neutros, synovium + some epithelium)

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19
Q

Seborrheic keratosis

who? what? histo? cause? association?

A

middle-aged to old pts

variable: macule, wart-like tan/brown epidermal tumor; few mm to cm

velvety/greasy surface; well-defined; “stuck-on” look

histo - small basal-like cells, variable pigment, hyperkeratosis (thick corneum) and KERATOCYSTS

cause - maybe FGFR-3 activating mutation

rapid onset of many = LESER-TRELAT SIGN of internal malignancy, often GASTRIC ADC (maybe via IGF-1 from tumor)

20
Q

Chancroid

microbe, microscopy, features of primary lesion

A

H. ducreyi

red papules erode into multiple, deep ulcers; yellow-gray base exudate (regional nodes may swell + ulcerate)

organisms clump in long parallel “SCHOOL OF FISH” strands

lesion IS painful (you “do cry” with ducreyi)

21
Q

Herpes

microbe, microscopy, features of primary lesion

A

HSV1/2

multiple, small, grouped ulcers; shallow red base

multinucleated giant cells + Cowdry type A bodies (nuclear inclusions) on Tzanck

lesion IS painful

22
Q

Granuloma Inguinale / Donovanosis

microbe, microscopy, features of primary lesion

A

Klebs granulomatis

extensive/progressive ulcers with NO node swelling; base may have granulation

deep gram-neg cytoplasmic cysts (Donovan bodies)

lesion NOT painful

23
Q

Syphilis

microbe, microscopy, features of primary lesion

A

T. pallidum

single, indurated, well-circ ulcer; clean base

spirochetes on DF

lesion NOT painful

24
Q

Lymphogranuloma venereum

microbe, microscopy, features of primary lesion

A

C. trachomatis

small, shallow ulcers; large, painful coalesced inguinal nodes (“buboes”)

cytoplasmic inclusion bodies in epithelium/leukocytes

lesion NOT painful (but nodes are!)

25
Q

Which two ulcerative STDs have PAINFUL initial ulcers?

A

Chancroid - H. ducreyi (you “do cry” with ducreyi)

Herpes - HSV1/HSV2

26
Q

Which 3 ulcerative STDs have PAINLESS initial ulcers?

A

Syphilis - T. pallidum

Granuloma Inguinale / Donovanosis - Klebs granulomatis

Lymphogranuloma venereum - C. trachomatis (has painful “buboes” of coalesced nodes after a painless ulcer)

27
Q

serotypes and complications (3) of lymphogranuloma venereum

A

L1-L3 (remember A-C ocular, D-K cause classic STI + inclusion conjunctivitis)

fibrosis
lymph obstruction
anogenital strictures + fistulas

28
Q

Supernumerary nipples

where? due to what?

A

anywhere along “embryonic milk line” from axilla to perineum; BILATERAL in 50%

failed involution of mammary ridge

29
Q

Similarities and differences between “ephelides” (freckles) and SOLAR LENTIGINES?

where found? what are they histologically?

size? in whom?

A

Both - sun-exposed areas; flat hyperpigmentations (macules)

Ephelides - increased melanin production; smaller; in kids

Solar lentigo - increased melanocyte number; larger; in adults

30
Q

Topical tx for acne vulgaris

drug and moa

A

Benzoyl peroxide

becomes benzoic acid which kills Propionibacterium acnes

31
Q

Topical anti-inflammatory for ACTINIC KERATOSIS

A

Diclofenac

32
Q

Topical abx for rosacea

A

metronidazole

33
Q

Topical analgesic for postherpetic neuralgia (+ other neuropathic pain)

A

Capsaicin

activates TRPV1, depletes substance P > nociceptive fiber dysfunction

34
Q

First-line tx for localized psoriasis (2 things)

A
  1. Corticosteroids - DIFLORASONE

2. Vit D analogs - CALCIPOTRIENE / CALCITRIOL (inhibit T cell + keratinocyte proliferation)

35
Q

Scabies

s/s? where on body? when is it bad + what causes it pathophysiologically?

A

RAPID spreading PRURITIC rash with RED PAPULES and EXCORIATIONS on the LIMBS

flexor surfaces of wrists, lateral surface of fingers, finger webs

worse at night; type IV HS rxn

36
Q

most specific finding in scabies

dx?

A

“linear burrows” - but can be obscured by scratch marks

micro of skin scrapings with mites, ova and feces

37
Q

infectious causes of SJS? (2)

how long after infection?

A

CMV
Mycoplasma

1-3 weeks after infection

38
Q

Leukocytoclastic vasculitis

aka what? causes (2 categories; 5 examples in one)?

A

cutaneous small vessel vasculitis

  1. Hepatitis B or C
  2. Drugs - penicillins, cephalos, sulfonamides, phenytoin, allopurinol
39
Q

Leukocytoclastic vasculitis (aka cutaneous small vessel vasculitis)

s/s?

A

NONBLANCHING palpable PURPURA usually on LEGS

shortly after new drug exposure, or with hep B/C

40
Q

Leukocytoclastic vasculitis (aka cutaneous small vessel vasculitis)

histo

A

inflamed small vessels with FIBRINOID necrosis

NEUTROPHILS in perivascular infiltrate in first 24 hrs with FRAGMENTED NUCLEI

later mononuclear cells

41
Q

Vitiligo

histology

A

partial or complete LOSS OF MELANOCYTES with a complete ABSENCE OF MELANIN

42
Q

postinflammatory hypopigmentation

what are the 2 mechanisms of hypopigmentation?

A
  1. REDISTRIBUTION of existing melanin within skin

2. REDUCED TRANSFER of melanin to keratinocytes

43
Q

Cafe au lait macules

histo

A

increased MELANOSOME AGGREGATES within melanocyte cytoplasm

44
Q

Lentigo

histo

A

a benign LINEAR MELANOCYTIC HYPERPLASIA

45
Q

Photoaging

what type of UV?
Mechanism of damage?
What is down- and up-regulated (3)?
Specific collagen + other molecule types?

A

UV-A penetrates deeper and create…

ROS > inflammatory cell receptor activation

  1. DECREASED collagen FIBRIL production
  2. INCREASED production of MMPs (eg, collagenase)
  3. INCREASED collagen CROSS-LINKS

Degrades TYPE I + III COLLAGEN and ELASTIN

46
Q

Photoaging

histo

(what happens to epidermis, dermis + junction)

A
  1. EPIDERMAL THINNING - corneum dessicates
  2. FLATTENED RETE RIDGES - at dermoepidermal junction
  3. in dermis, less fat, vessels, hair follicles, sweat + sebaceous glands
47
Q

Skin lesion commonly found in Turner or Downs patients

when, where and made of what?

A

Cystic Hygroma

  • at birth
  • lymphatic cyst lined with thin endothelium
  • posterior neck + lateral chest wall

*USMLE* (28 decks)

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