Infectious Dermatology Bacterial. Viral. Fungal. and EMERGENCIES

What is follicular?

Pattern involving hair follicles

How do the lesions often emerge in follicular?

Papular or pustular with a central emerging hair

What is folliculitis?

Infection of the hair follicle +/- pus in the ostium (where the hair shaft emerges) of the follicle

What are predisposing factors to folliculitis?

Shaving hairy regions

Occlusion of hair bearing areas

What are bacterial agents of folliculitis?

S. aureus

Pseudomonas aeruginosa

What are symptoms of folliculitis?

Slight burning

Tenderness

May be mildly pruritic

What is the classic hallmark of folliculitis?

Hair shaft emerging from the center of a pustule

Consider culture to differentiate bacterial vs non bacterial

What should you avoid during folliculitis management?

Avoid occlusion / friction, ex: wear looser clothing

How to treat bacterial folliculitis?

Topical antibiotics (clindamycin) +/- BPO wash

How to treat fungal folliculitis?

Topical antifungals (Ketoconazole cream) +/- oral antifungals (ex: fluconazole)

What is a furuncle?

Single follicle - based abscess

Localized, painful nodule

What is a carbuncle?

Multiple adjacent follicle abscesses

Larger, deeper, more inflammatory

May have systemic symptoms (fever, leukocytosis)

What are common sites of furuncle and carbuncles?

Neck, axillae, buttocks, thighs

What is an abscess?

Localized pus collection +/- follicle involvement

What is pseudofolliculitis barbae?

Not an infection

Foreign body inflammatory reaction from ingrown hairs

Occurs in hair bearing areas after shaving

Papules and pustules that may mimic folliculitis or acne

M/C in curly hair

Chronic/severe cases causes keloids

What is the treatment of pseudofolliculitis barbae?

Avoid close shaving

Reduce friction and irritation

Topical retinoids

Topical antibiotics ONLY if secondary infection

What are bacterial skin infections most commonly caused by?

Staphylococcus and streptococcus species

Entry often through disrupted skin barrier

What is non-bullous impetigo?

Superficial bacterial infection

Honey-colored crusts are classic

Highly contagious, common in children

What causes non-bullous impetigo?

Staph aureus or Streptococcus pyogenes (group A strep)

How do bacteria enter the body in non-bullous impetigo?

Through breaks in the skin (eczema)

What does bullous impetigo involve?

Toxin mediated Staph aureus

Large, fluid-filled, painless blisters that stay intact longer and often appear on the trunk or diaper area

What is ecthyma?

More serious, deeper form that penetrates into the dermis, causing painful punched out ulcers with yellow crusts and raised, purple borders

What is treatment for impetigo?

Topical Mupirocin

What is the prevention of impetigo?

Keep fingernails short to prevent scratching which can lead to spread

What causes erysipelas?

Group A Streptococcus (Strep Pyogenes)

How does erysipelas look like?

Bright red, raised, sharply demarcated borders

Fever and chills are common

What are the common locations of erysipelas?

Face (Classic)

Lower extremities

What is the treatment of erysipelas?

Pencillin

What is cellulitis?

Acute bacterial infection of the dermis and subQ tissue

Ill-defined borders

What are risk factors for cellulitis?

Skin barrier disruption

Tinea pedis

Chronic edema/venous insufficiency

Diabetes

Immunosuppression

Why do clinicians mark cellulitis?

Monitor progession

Assess treatment response

Distinguish infection from inflammation

When does cellulitis become emergency?

Signs of sepsis

Systemic signs

Rapidly spreading erythema

Immunocompromised patient

Severe pain out of proportion (think nec fasc)

What is necrotizing fasciitis?

Rapidly progressive, life-threatening soft tissue infection

Involves deep fascia with secondary necrosis of skin and subq tissue

What are the 5 Ws of necrotizing fasciitis?

Worsening pain

Worsening edema

Wound appearance

Worsening systemic signs

Worsening response to treatment

What should you not do with necrotizing fasciitis?

Do not manage as simple cellulitis

Do not wait for cultures

Do not rely on imaging to rule it out

TIME = TISSUE

Who is at risk for nec fasc?

Patients with diabetes

Immunosuppression

Chronic wounds

Recent surgery or trauma

What is the definitive treatment of abscesses?

If fluctuant, I&D

What is paronychia?

Infection of the nail margin

Red, swollen, tender

What is a felon?

Deep pulp space abscess of the fingertip

Severe throbbing pain

Tense swelling of distal finger

Can compromise circulation

What is management for paronychia or felon?

Early/Mild - warm soaks, topical antibiotic

PUS or FLUCTUANT -> incision and drainage

Felon = deeper -> higher risk of necrosis

What are complications of untreated skin abscesses?

Spread of infection

Formation of multiple abscesses

Skin scarring

Chronic infections

Damage to deeper tissues

What are systemic complications?

Bacteremia

SEPSIS

If the skin looks bad, but the patient looks worse, worry about what?

Sepsis

What is sepsis?

Life-threatening organ dysfunction caused by infection

If pus is present, what should you do?

Culture it

When should you NOT culture?

Uncomplicated impetigo

Mild cellulitis responding to treatment

Classic folliculitis

Typical acne

Uncomplicated eczema or dermatitis

HSV-1 is classically what?

Oral

HSV-2 is classically what?

Genital

What is HSV?

Painful grouped vesicles on an erythematous base

How to diagnose HSV?

Tzanck smear: multinucleated giant cells

What is the treatment for HSV? (no cure)

Acyclovir

Valacyclovir

Famcyclovir

What is the varicella chicken pox look like?

Dew drop on a rose petal

How long is chicken pox contagious until?

Until lesions have crusted

What should you avoid in chicken pox?

Aspirin (Reyes Syndrome)

What is herpes zoster virus (shingles)>

Painful, unilateral rash

Dermatotomal distribution

What are the clinical features of zoster?

Pain, burning, or tingling often precedes rash

Grouped vesicles on an erythematous base

Unilateral and does not cross the midline

What is postherpetic neuralgia?

Chronic neuropathic pain after rash resolution

PHN risk increases with age (esp >50)

Antiviral (cyclovirs) reduces severity and risk of PHN risk

Shingles vaccine recommended for prevention

What can herpes simplex cause on the eye?

Herpes keratitis (corneal infection)

Symptoms: painful red eye, photophobia, blurred vision

Classic finding: dendritic corneal ulcer on fluorescein exam

DON'T USE TOPICAL STEROIDS

What do bites/stings often mimic?

Cellulitis or abscess

What are scabies?

Intense nocturnal pruritus

Burrows

Webs spaces

What is treatment of scabies?

Permethrin 5% cream (repeat treatment)

What is pediculosis?

Lice

Head, body, or pubic lice

Scalp pruritus

Nits (eggs) attached to hair shafts

What is treatment to pediculosis?

Permethrin 1% lotion

What type of rash occurs in benign drug eruptions?

Morbilliform/maculopapular eruption

What is the timing of benign drug eruptions?

Appearing 3-14 days after starting a new med

What are viral exanthems common in?

Children (but can also occur in adults)

Diffuse, symmetric, maculopapular rash

Often starts on the trunk and spreads

What is hand foot mouth disease?

2/2 Coxsackie Virus

Oral ulcers (painful)

Vesicles on hands and feet

May have fever, sore throat, malaise

What is mollucsum contagiosum caused by?

Poxvirus

Pearly, dome shaped papules

Central umbilication - key feature

What is treatment for molluscum contagiosum?

Cryotherapy

Cantharone

Do warts have roots?

No

What are verruca vulgaris (warts) caused by?

HPV

What are classic features of verruca vulgaris?

Disrupts normal skin lines

Black dots = thrombosed capillaries

Where are verruca vulgaris (common) located?

Anywhere

m/c hands, knees & periungal

What are plantar warts located?

Soles

Painful with pressure

Thrombosed vessels after paring

What are flat warts?

Smooth, flat-topped

Common in children and after shaving

Where is condyloma acuminatum found?

Genital/perianal

STD

What is the treatment of warts?

Cryotherapy

What are fungal infections caused by?

Dermatophytes

What does tinea infections (dermatophytes) look like?

Annular plaques with central clearing

Scaling, advancing borders

Often pruritic

What is candidiasis?

Erythematous patches with satellite lesions

Occurs in intertriginous areas (skin folds)

What is the treatment for oral candidiasis?

Topical nystatin (swish and swallow)

What is onychomycosis?

Fungal infection of the nail

Thickened, yellow, brittle nails

Usually from untreated tinea pedis

What is the treatment for onychomycosis?

Topical ciclopirox solution

Topical jublia

Oral terbinafine

What is erythema multiforme?

Acute self limited Type IV hypersensitivity reaction

What causes erythema multiforme?

HSV triggered

Medications ex: sulfa drugs

What are the classic presentations of erythema multiforme?

Target lesions

Dusky violaceous

What are general red flags of erythema multiforme?

Prodrome - fever, malaise, sore throat preceding a rash

Dusky or targetoid lesions

Blistering w/ epidermal detachment

What is SJS / TEN?

Not an infection

Severe mucocutaneous drug reaction that causes blistering

Dusky purpura with blistering, what should you check for?

SJS/TEN

What are causes of SJS?

Sulfonamides

Allopurinol

Tetracycline

Anticonvulsants

NSAIDs