Dermatology

Question 1

Cellulitis

Answer 1

Acute bacterial infection of the skin
Causes: in adults most common are S. Aureus, GAS. In kids: HIB, GAS, S. aureus. varies with location.
S/Sxs: local erythema, heat, edema, tenderness with lymphangitis and LA. Systemic sxs such as fever, chills, tachycardia, HA, hypotension.
Distribution: Adults: lower legs most common. Children: cheeks, periorbital, head, neck
Diagnosis by H&P, CBC, culture of exudates or aspirate.
DDX: DVT, gout, CPPD, septic arthritis, stasis dermatitis, insect bite, erysipelas
Notes: Solid swelling, see if area is growing

Question 2

Cutaneous abscess

Answer 2

Localized collection of pus under the skin
S/Sxs: painful, tender, indurated and erythematous, varying in size from 1-3cm. Can be accompanied by lymphangitis, LAD, cellulitis.
Dx: H&P, CBC. Gram stain or culture
DDX: hidradenitis suppurativa (arms/sacrum - boils that ooze and looks like an abscess) ruptured epidermal cysts
Notes: Drain

Question 3

Erysipelas

Answer 3

Superficial cellulitis with dermal lymphatic involvement (streaking)
Cause: GAS, immunocompromise
S/Sxs: shiny, raised, indurated and plaque like lesions with distinct margins. High fever, chills, malaise possible. Sharp borders, raised, red, hot plaque that spread rapidly. Regional LAD and tenderness, and may see vesicles, bullae, petechiae, itching, burning, and pain may be severe. Red, painful streaks along lymph.
Complications: scarlet fever, fat necrosis, gangrene. SUDDEN ONSET
Distribution: legs most common, then face.
Dx: H&P, CBC, blood culture in toxic appearing patients.
DDX: Face - herpes zoster, contact derm.

Question 4

Erysipeloid

Answer 4

Like erysipelas except a different bacteria (erysipelothrix). Violaceous on the hands and forearms and is NOT HOT, though may be tender with fever and malaise. RARE
Notes: Common with animals, more purple than red. Mild

Question 5

Erythrasma

Answer 5

Superficial intertriginous infection with Corynebacterium.
S/Sxs: occurs in toe webs, between fingers, genitals with scaling, fissuring and maceration. May be patchy on the trunk.
Dx: coral red fluorescence with Wood’s lamp, no hyphae, skin scraping with KOH
DDX: tinea, candida

Question 6

Folliculitis

Answer 6

Inflammation of the hair follicle
Very common
Cause: S. aureus, fungal, persistent trauma, shaving
S/Sxs: pustule or inflam. nodule that surrounds a hair follicle. Superficial or deep, mild itching or pain. Abrupt onset may be chronic
“Hot tub” folliculitis - caused by pseudomonas infection - smells like grapes - onset 8hrs-5 days post hot tub. Trunk, groin mostly.
Distribution: anywhere but hands and feet
Dx: by examination, KOH to r/o dermatophyte
DDX: acne, follicular keratosis
Notes: treat with botanical, nutrition, omega 3 FA

Question 7

Furuncle (boil)

Answer 7

Acute tender nodules, caused by S. Aureus
Very painful
S/Sxs: A deep dermal or subQ red swollen and painful mass and drains to the surface. Pustule 5-30mm with central necrosis and pus discharge. May be recurrent. AFEBRILE.
Age: uncommon in children
Distribution: neck, under breasts, buttocks, groin most common
Dx: by examination. Culture to r/o MRSA
DDX: foliculitis, Hidra suppurativa, insect/spider bites, ruptured pilar cysts, cystic acne.
Notes: treat with poultice (onion, potato)

Question 8

Carbuncle

Answer 8

Cluster of furuncles with multiple draining orifices.
S/Sxs: neck, face, breasts and butt. uncomfortable, maybe painful, with FEVER.
Dx: by examination, culture if recurrent.
Notes: treat with poultice, herbs

Question 9

Impetigo

Answer 9

Superficial acute skin infection with crusting
*Honey colored crust
Cause: S. pyogenes, S. aureus. Warm moist climate, poor hygiene
S/Sxs: clusters of vesicles or pustules that rupture and develop honey colored crust. Scaling borders. Itchy.
Distribution: face, shins, extensor surfaces of forearms, lips, around mouth
Age: common in children
Dx: by examination. Culture to r/o MRSA
DDX: atopic, contact derm, periorbital derm, herpes simplex, herpes zoster, tinea

Question 10

Candidiasis

Answer 10

skin infection with candida, mostly candida albicans 70-80%. Causes: Immunosuppression, sugar dysregulation, antibiotics, Oral BC,
S/Sxs: intertriginous, erythematous, well-demarcated, pruritic patches of varying shapes and sizes. Intense inflammation with satellite lesions around main area.
Types: balantitis (Penis), diaper derm, intertrigo, vulvovaginitis, oropharyngeal.
Dx: by examination, presence of yeast and pseudophytes on KOH prep, fungal culture or DNA probe.
DDX: changes with location. Dermatophytoses, allergic dermatitis, herpes, psoriasis, strep cellulitis, erythasma

Question 11

Dermatophytoses

Answer 11

Fungal infections of keratin in the skin and nails. Caused by epidermophyton, microsporum, and trichophyton.
S/Sxs: vary by site. Recurrent with little or no inflammation. Mildly pruritic, erythematous scaling lesions.
Dx: by appearance, Wood’s lamp, skin scraping and KOH prep.

Question 12

Tinea barbae

Answer 12

Barbae (beard). Uncommon. Develops slowly. 2 patterns: ringworm and follicular. Pruritic, at times painful and swollen.
Fungal cultures and biopsy can be helpful with dx.

Question 13

Tinea capitis

Answer 13

Capitis (head). Caused by trichophyton tonsuring. More common in african americans and hispanic. Children most effected.
4 patterns: seborrheic derm, inflammatory, black dot pattern and pustular.
S/Sxs: change with each. KOH exam of lesions hairs. Wood’s lamp exam of infected hairs reveals characteristic silver-blue fluorescence.
DDx: Psoriasis, seborrheic dermatitis

Question 14

Tinea Corporis

Answer 14

Carpers (body). S/Sxs: pruritic, circular or oval, erythematous, scaling patch/plaque that spreads centrifugally. central clearing follows. Red slightly raised. KOH will show hyphae.
DDx: pityriasis rosea, drug eruptions, nummular term, erythema multiform, tine versicolor, psoriasis.

Question 15

Tinea Cruris

Answer 15

Cruris (crotch). “Jock itch” Causes: obesity, diabetes and immunodeficient states.
S/sxs: erythematous patch on the inner aspect of one or both thighs. Spreads centrifugally. Slightly elevated, erythematous, sharply demarcated border that may show tiny vesicles that are visible only with a hand glass. Spares the scrotum. M>F.
Dx: KOH prep from scraping of an active border.
DDx: contact derm, psoriasis, candida, erythasma seborrheic derm.
Notes: vesicles think derm, herpes, fungus.

Question 16

Tinea Pedis

Answer 16

Pedis (foot). “Athletes foot”. Common, intensely pruritic, sometimes painful, erythematous vesicles or bullae between the toes or on the soles. Called an Id reaction (immune response to infection, gets a distant reaction elsewhere such as the hands).
Dx: skin scraping
DDx: dyshidrotic eczema, contact derm, psoriasis.
Note: chronic althetes foot are best treated with the big anti-fungals.

Question 17

Tinea versicolor

Answer 17

Superficial fungus infection with Malassezia furor (yeast)
S/Sxs: Hypopigmented, hyperpigmented, or erythematous merciless with scaling patches. Lesions are asx. Red, white, or dark patches.
Distribution: trunk and proximal upper extremities.
Dx: “spagetti and meatballs” microscopy viewed. Wood’s lamp.
DDx: Vitiligo, pityriasis rosea, tinea corporis, seborrheic, erythasma

Question 18

Cutaneous Larva Migrans

Answer 18

“creeping eruption” caused by hookworm larva from cat/dog feces.
S/Sxs: intense pruritis, erythema and papules at site of entry, winding tail of inflammation. Serpiginous, usually occurs 3 weeks after exposure.
Distribution: feet/ankles, butt, backs of legs and back
Dx: history and appearance, CBC can show eosinphila, CXR
DDX: scabies

Question 19

Lice (Pediculosis)

Answer 19

Wingless blood sucking insects that infect the head, body or pubis.
S/Sxs: intense pruritis, excoriations from scratching. Red punch from bites. Nits on hair shaft 1cm from scalp- gray/white. May see brown specs of excrement on hair or clothing.
Distribution: scalp, body hair, pubic hair.
Dx: living lice demonstration, wood’s lamp
DDx: seborrheic derm, impetigo, insect bites.

Question 20

Scabies

Answer 20

Infection of skin with scabies mite sarcoptes.
S/Sxs: burrows are fine, wavy lines in the skin 2-10 mm long, covered by lichenified skin. Intensely pruritic, esp. at night. erythematous papillose present sometimes. Others in living quarters affected.
distribution: hands, arms, feet, gluteal fold, axilla, back of knees.
Dx: burrows are pathognomonic. Often made by Hx and PE.
DDx: insect bites, fungus, eczema, folliculitis, impetigo

Question 21

Molluscum contagiosum

Answer 21

caused by pox virus in epidermal cells.
S/Sxs: smooth flesh colored umbilicated dome, hard. Cheesy core, may become inflamed. Asx. up to 15mm in diameter, lesions persist of 6-9 months.
Age: Any but more common in 3-9yrs
Distribution: face, arms, chest, genitals,
Dx: by appearance. Biopsy will show molluscum bodies in keratinocytes. Biopsy should be used in immunocompromised patients.
DDx: folliculitis, milia, verrucae
Note: Normally self-limiting, often confused with warts.
Keynote: dimple in middle

Question 22

Warts (Verrucae vulgaris)

Answer 22

Benign contagious neoplasms caused by HPV
Common wart: dome shaped, round or irregular, rough; colors can be gray, yellow, brown, black, skin colored. 2-10mm usually asx.
Distribution: hands, knees, genitalia, feet.
Age: any but peaks at 12-16 yrs
Skin lines are interrupted by hyperkeratosis
Black punta when scraped with pinpoint bleeding
Types: Filiform, flat, plantar, mosaic, condylloma accuminata (genital).
Dx: by appearance, biopsy if necessary to r/o SCC
Notes: be concerned about possible child abuse in children with genital warts

Question 23

Varicella

Answer 23

“Chicken pox”
Acute highly contagious vesicular eruption caused by a primary infection with varicella HHV-3
S/Sxs: prodrome with malaise, chills, HA, sore throat, anorexia and dry mouth. Then the rash starts and itching is severe. Lesions are papules, merciless, vesicles, pustules and crusts all at the same time.
20% of patients vaccinated will still get infection.
Distribution: begins on trunk and spreads to face and extremities. Most lesions present on trunk, can also occur in mouth and vagina.
Infectious from 2 days before ask until all lesions crust over.
Dx: Characteristic rash, culture or tzanck smear in some cases.
DDx: other viral diseases, contact term, zoster, folliculitis, impetigo

Question 24

Herpes Simplex

Answer 24

Recurrent viral infection with intraepidermal infection by HSV 1 or 2.
S/Sxs: single or cluttered vesicles. systemic symptoms with primary infections: fever, malaise, myalgia, HA, and regional LA. Prodromal period of tingling or discomfort in many, then appearance of small vesicles on a red base. They often rupture and ulcerate. Often painful. Heal within 2-6 weeks.
Distribution: mouth, eyes, genitals
Herpetic whitlow: infects distal phalanx with a very painful lesion that swells
Dx: characteristic lesions. Tzanck smear. Definitive dx is with culture of freshly ulcerated lesion.
DDx: impetigo, eczema, zoster, hand foot and mouth, aphthous stomatitis.
Notes: virus lives on nerve root. cold weather can trigger sxs.

Question 25

Herpes Zoster (shingles)

Answer 25

Latent varicella HHV 3 infection
S/Sxs: virus remains in the nerve roots and erupts along the associated dermatome. May start with radicular pain and itching for 2-3 days, followed by herpetic rash. There may be severe pain, scarring or post-herpetic neuralgia which can be debilitating. Lesions last 5 days. Pain may last weeks, months, years or forever.
Distribution: follows dermatome, never crosses midline
Dx: pathognomonic rash, tzanck smear. differentiate virus by culture.
DDX: changes with stage of dz. Before rash onset: MI, pleurisy, migraine. After lesions appear: HSV, primary varicella.