USMLE World Dermatology

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USMLE World Dermatology

What is the strongest risk factor for malignancy?

recently changed mole (RR of 10)

Sun sensitivity increases risk by 2-3 fold
Positive FHx: 8 fold
Previous sunburns: RR of 2

How does angioedema present?

rapid onset
- noninflammatory edema of face, limbs, genitalia
- laryngeal edema
- edema of bowels resulting in colicky abd pain

What is the pathology behind angioedema?

C1 inhibitor deficiency, dysfxn, destruction
- C2b and bradykinin increased (edema producing factors)

most common acquired form of angioedema is ACEI use

What are cherry hemagiomas?

small red cutaneous papules common in aging adults
Do not regress spontaneously and typically increase in number w/ age
Light microscopy: proliferation of capillaries and postcapillary venules in papillary dermis

What are strawberry hemangiomas?

infantile hemangioma that appears during first weeks of life, initially grow rapidly and then involute by 5-8yrs

What are cavernous hemangiomas?

dilated vascular spaces w/ thin-walled endothelial cells
present as soft blue compressible masses up to a few cm in size
- seen on skin, mucosa, deep tissues, and viscera
- less likely to regress spontaneously than capillary hemangiomas
- cavernous hemangiomas of the brain and viscera are assoc w/ von Hippel-Lindau disease

What are cystic hygromas?

lymphatic cysts lined by a thin endothelium
benign tumors
present at birth and are most commonly located on the neck and lateral chest wall.
Assoc w/ Turner's syndrome and Down syndrome

How is hypothermia tx?

rapid rewarming w/ warm water
extremity should be immersed in warm water which is continuously circulated

What kind of hypersensitivity is allergic contact dermatitis?

Type IV (cell mediated)

How does squamous cell carcinoma present microscopically?

invasive cords of squamous cells w/ keratin pearls

**How is moderate- to-severe acne tx?

**oral isotretinoin

**How is acne predominantly non-inflammatory comedones tx?

**topical retinoids

**How is mild inflammatory acne tx?

topical benzyl peroxide
topical abx (erythromycin, clindamycin, tetracycline)
or combo

**How is moderate-to-severe inflammatory acne tx?

**oral abx (most common tetracyclines)

What is bullous pemphigoid?

Benign pruritic disease
tense blisters
oral lesions rare
immunofluorescence shows IgG and C3 deposits in the dermal epidermal jxn

What is bullous impetigo?

contagious infxn of the skin caused by Staph, Strep or both
- macules, vesicles, bullae, honey colored crusts, have red denuded areas when removed
- bullous type is assoc w/ Staph

What is erythema multiforme?

macular, papular, bullous or purpuric
"target" lesions noted
most commonly involved sites: extensor surface, palms, soles, and mucous membranes

What is dermatitis herpetiformis?

manifested by pruritic papules, vesicles over the elbows, knees, buttocks, posterior neck, and scalp
Immunofluorescence: granular IgA deposits along dermal papillae
Can detect circulating anti-endomysial antibodies can be detected in all pts (gluten-sensitive enteropathy)

What is pemphigus vulgaris?

mucocutaneous blistering disease that is characterized by flaccid bullae and intercellular IgG deposits in the epidermis
Autoabs are formed against desmoglein (adhesion molecule)

What is the tinea versicolor?

superficial fungal infxn of the skin
pale, velvety pink or whitish hypopigmented macules that do not tan and do not appear scaly, but scale on scraping
Caused by Malassezia furfur
areas never tan
skin scrapings after KOH preparation reveals large, blunt hyphae and thick-walled budding spores ("spaghetti and meatballs" appearance)

How is tinea versicolor tx?

selenium sulfide lotion and ketaconazole shampoo

How do you distinguish between tinea versicolor and vitiligo?

vitiligo usually presents w/ peri-orificial lesions or lesions on the tips of fingers
total depigmentation and not just lessened pigmentation

What is Pityriasis rosea?

oval, fawn-colored plaques that measure up to 2cm in diameter and occur in a Christmas tree pattern.
initial lesion (herald patch) that is followed by generalized eruption in 1-2 wks

What is the most common cause of acquired angioedema?

ACEI
- can occur at any time, not just within/wks of starting meds

What is molluscum contagiosum?

single or multiple, rounded, dome-shaped papules w/ central umbilication
ASx lesions
no systemic signs
initially firm, but may later soften and suppurate
Children: trunk and extremities are mainly involved
Adults: face, lower abd, genitals
Sexually active: penis, pubis and inner thighs
Seen in AIDS, especially if less than 100/ul

What causes molluscum contagiosum?

poxvirus

What is miliaria?

heat rash
superficial aggregated small vesicles, papules or pustules over the trunk
associated w/ burning and itching

What is tinea corporis?

characterized by ring-shaped scaly patches w/ central clearing and distinct borders

How is tinea corporis tx?

2% antifungal lotions and creams (terbinafide)
OR systemic tx w/ griseofulvin (extensive disease) offers good relief

What is TEN?

severe mucocutaneous exfoliative disease
- erythematous morbilliform eruption that rapidly evolves into exfoliation of the skin
- positive Nikolsky's sign
- oral mucosa shows painful blisters
- neg drug rxn: sulfonamides, barbituates, phenytoin, NSAIDs

What is the difference between TEN and Steven Johnson Syndrome?

Steven Johnson Syndrome: up to 10% of BSA involved
TEN: >30% of BSA is involved

What is Staphylococcal scalded skin syndrome?

syndrome of acute exfoliation of skin caused by toxin that is produced by phage group 2 Staph
Skin is tender and warm, with a diffuse erythematous rash that is sandpaper-like.
Bullae, positive Nikolsky's sign, facial edema, perioral crusting, and dehydration are other features.
Children <6yrs of age

What is rosacea?

30-60yo
telangiectasia over the cheeks, nose, and chin
Flushing of these areas typically precipitated by hot drinks, heat, emotion, and other causes of rapid body temp changes

How is rosacea tx?

Flagyl

How does basal cell carcinoma present?

slow-growing nodules w/ pearly quality and rolled border
often telangictasias overlying and at the periphery of the lesion
bleeding and ulcerations are common features
thinning or loss of eyelashes in the region of the tumor is typical
most common location for eyelid BCCs is the lower eyelid margin

What is Keratoacanthoma?

rapidly growing "volcano-like" nodule w/ a central keratotic plug
self-limited lesion
tx like SCC

What conditions are assoc w/ vitiligo?

autoimmune processes
- pernicious anemia
- autoimmune thyroid disease (Graves' or chronic autoimmune thyroiditis)
- type 1 diabetes mellitus
- primary adrenal insufficiency
- hypopituitarism
- alopecia areata

What type of skin condition is associated w/ Parkinson's disease?

seborrheic dermatitis
- waxy scales w/ underlying erythema on the scalp, central face, presternal region, interscapular areas, umbilicus and body fluids
also assoc w/ HIV

What is porphyria cutanea tarda?

assoc w/ Hep C
condition that arises from the deficiency of uroporphyrinogen decarboxylase (enezyme in heme synthesis pathway)
- painless blisters
- increased skin fragility on the dorsal surfaces of the hands, facial hypertrichosis and hyperpigmentation
- triggered by ingestion of certain substances (ethanol, estrogens)

DX: elevated urinary porphyrin levels

TX: phlebotomy or hydroxychloroquine may provide relief, interferon-alpha (esp in pts w/ Hep C)

What is acantholytic dermatosis?

Grover disease
pt presents w/ pruritus erythematous to brown keratotic papules over anterior chest, upper back, lower rib cage
unknown etiology

What condition is assoc w/ dermatitis herpetiformis?

Celiac sprue
- pts may have GI sx suggestive of malabsorption
- presence of anti-endomysial abs
- increased risk for gastro-intestinal lymphomas

How is dermatitis herpetiformis tx?

dapsone

What vitamin supplementation can be added to tx measles?

Vitamin A

How is melanoma dx?

excisional biopsy w/ narrow margins
TX:
- if depth is < 1mm, excise w/ 1cm tumor free margin
- if depth >1mm, sentinal lymph node study needed

What class of abx cause photosensitivity?

tetracyclines
- doxycycline

**What is the best form of photo-protection?

**sun avoidance > sunscreen

When should sunscreen be applied?

15-60 min prior to sun exposure

**What is herpetic whitlow?

**viral infxn of the hand
caused by Type 1 or 2 herpes simplex virus, and is self-limiting
at risk: health care workers who come in direct contact w/ infected orotracheal secretions

What virus causes measles?

paramyxovirus

How does measles present?

1) exposure to virus (transmitted via respiratory droplets)
2) prodrome after 10 days (coryza, conjunctivitis, cough = 3 Cs)
3) Koplik's spots (red spots w/ bluish specks over the buccal mucosa, opposite the premolar tooth) and slowly fade once the rash appears
4) characteristic rash is erythematous maculopapular, initially over the face and then spreads to cover the entire trunk and extremities

What drugs can trigger bullous pemphigoid?

autoimmune blistering disorder
- furosemide
- NSAIDs
- captopril
- penicillamine

What does direct immunofluorescence reveal in bullous pemphigoid?

IgG and C3 deposits linearly along the basement membrane zone

What is warfarin-induced skin necrosis?

serious complication of oral anticoagulants
- breasts, buttocks, thighs, and abdomen
- pain, bullae formation and skin necrosis
- occurs weeks after starting therapy
Tx: Vita K admin
exchange and use heparin instead

How does scarlet fever present?

toxin-related process from Group A strep
children
prodrome of fever, headache, vomiting, and sore throat
12-28hrs
fine pink blanching papules appear on the neck and upper trunk and quickly generalize w/ flexural accentuation
eruption is rough, sandpaper-like texture

How does rubella present?

1) exposure to virus (transmitted via respiratory droplets)
2) development of fever, malaise, tender suboccipital adenitis after 14-21 days
3) characteristic rash appears 1-5 days later (maculopapular rash initially on the face, and then spreading to involve the trunk and extremities, lasting for less than 3 days)

polyarthralgia is common in adults. posterior cervical and posterior auricular lymphademopathies are common.

What conditions predispose pts to molluscum contagiosum?

cellular immunodeficiency
corticosteroid use
chemotx

What is ichthyosis vulgaris?

normal skin at birth with gradual progression to dry scaly skin

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