Skin Infections - Plaza Flashcards
Impetigo
Superficial or deep?
Offending microbe?
Appearance?
Sites of infection?
Impetigo
Superficial.
Staph Aureus (sometimes Strep Pyogenes)
“Honey-crusted” vesicles. May form bullae.
Mouth, nose, and extremities.
SSSS
Superficial or deep?
Offending microbe?
Appearance?
Sites of infection?
SSSS
Superficial (splits stratum granulosum).
Staph Aureus (secretes Exfoliatins A/B).
Sudden onset macular eruption followed by large flaccid bullae.
Face, neck, & trunk (including intertriginous).
SSSS
How are adults and children affected differently?
SSSS
More common in children, & with good prognosis. Adults tend to experience staph septicemia.
Cellulitis
Superficial or deep?
Offending microbe?
Appearance?
Sites of infection?
Cellulitis
Deep
Beta-hemolytic Strep and/or Coag+ Staph
Tender, diffuse erythema.
Legs.
Erysipelas
Superficial or deep?
Offending microbe?
Appearance?
Sites of infection?
Erysipelas
Deep (involves dermal cutaneous lymphatics)
Strep Pyogenes (sometimes Staph Aureus or other Strep)
Sharply defined edematous, erythematous, painful plaques.
The legs of the elderly. Faces?
Verrucae
Superficial or deep?
Offending microbe?
Appearance?
Sites of infection?
Verrucae
Superficial (epidermal)
HPV (usually low risk serovars 6, 11)
Papular lesion: Pearly/fiiform/fungating/cauliflower- or plaque-like. (true of condyloma acuminatum, anyway)
Many sites; hands/feet, eyelids, mouth, genitals.
Verrucae
Describe their pathology.
How do they appear on histology?
Verrucae
HPV infection results in epidermal hyperplasia (especially s. granulosum) and koilocytosis of the upper epidermis.
Lesion is very papillary, extending above the normal skin line. Look for keratohyaline granules & intracytoplasmic aggregates.
Distinguish between the type types of Herpes simplex viruses and the skin symptoms they cause.
HSV-1 common in childhood, affects lips (cold store / gingivostomatitis)
HSV-2 seen after puberty (early >> child abuse)
Both cases: clear vesicles that heal without scarring.
**1 above the waist, 2 below it.
Describe the route of transmission, appearance, and complications of varicella. Who is usually affected?
Varicella (chickenpox) usually causes infection in children via respiratory route. A macular/vesicular/pustular rash forms. Pneumonia and cerebritis are complications (as is Reye’s syndrome).
What is the appearance and etiology of Shingles?
Varicella-Zoster recurs occasionally in elderly & IC’d patients.
Chickenpox-like rash (macular/vesicular/pustular) unilaterally in the dermatome of the sensory nerve in which the varicella was latent.
Describe the pathology of the skin findings of Herpes virus infections.
In both HSV & VSV:
Acantholysis (separation of dermis & epidermis)
Multinucleated keratonocytes with intranuclear (“Cowdry Type A”) inclusions.
Peri/intraneural inflammation.
What is a Tzank smear? What is it sensitive for?
A giemsa stain of a vesicular smear. Looks for multinucleated giant cells, found in herpesviruses (and, CMV, Pemphigus Vulgaris)
Molluscum Contagiosum
Offending microbe?
Appearance?
Sites of infection?
Who is affected?
Molluscum Contagiosum
Poxviruses.
Crater-like nodule with eosinophilic (“Henderson-Patterson”) cytoplasmic bodies.
Eyelids, face, axilla. Sometimes genitals (spread by self-inoculation)
Generally children & the IC’d.
Scabies
Offending microbe?
Appearance?
Sites of infection?
How is it diagnosed?
Scabies
Sarcoptes Scabiei (4-legged arthropod mite)
Extremely pruritic papulovesicular eruption. *4wks after initial infection.
Fingers, hands, axilla, waistband, umbilicus, penis.
Scrapings of the skin to reveal the mite or its eggs.
Dermatophytosis
Offending microbe?
Appearance?
Sites of infection?
How is it diagnosed?
Dermatophytosis
Microsporum/Epidermophyton/Trichophyton (organisms have location preferences, eg T. Tonsurans in scalp).
Scaly, erythematous, annular plaques.
Scalp (capitis), trunk (corporis), beard (barbae), groin (cruris), feet (pedis).
KOH treatment of scraping (or PAS stain) to reveal septate hyphae. Wood’s light?
