Cutaneous infections Flashcards
Impetigo
Common superficial bacterial infection
highly infectious (direct contact)
Staphylococcus aureus (and less commonly streptococcus pyogenes)
Small vesicles that rupture and are replaced by thick yellow crust (honey-colored)
The mouth, nose, and extremities most commonly affected
Bullous impetigo
Caused by epidermolytic toxin of staph aureus
Toxin-mediated type of exfoliative dermatitis
Toxigenic strain of Staph aureus (phage group II, type 71)
Two exotoxins epidermolytic toxin A (ET-A), and ETB
Cause intraepidermal splitting through the granular layer by targeting desmoglein 1
Staphylococcal Scalded skin syndrome
Staphylococcal Scalded skin syndrome
sudden onset of skin tenderness and a macular eruption
Followed by development of large flaccid bullae
Face, neck, and trunk including the axillae and groin
Mucous membranes are not involved
Good prognosis in children
In adults a staphylococcal septicemia may ensue
Cellulitis
Deep pyogenic infection
Diffuse inflammation of the Connective tissue of the skin and/or the deeper soft tissues
Most common on legs
Expanding area of erythema (tender)
B-hemolytic streptococci and or coagulase-postive staphylococci
Other organisms are implicated in the etiology of cellulitis
Erysipelas
Bacterial skin infection involving the upper dermis (superficial cutaneous lymphatics)
Sharply outlined edematous, erythematous, tender and painful plaque (elevated borders)
More common on lower extremities
Most prevalent in elderly
Strep. pyogenes, is the most common organism (other streptococci or S. aureus)
Verrucae aka Warts
Viral warts
HPV (DNA virus), Verruca vulgaris, plantar warts, anogenital warts, generally self limited
Regress spontaneously within 6 months to 2-3 yrs
low risk and high risk HPV
Most warts are caused by low-risk HPV
Pathology: verrucous epidermal hyperplasia, Koilocytosis (cytoplasmic vacuololization of upper layer of epidermis)
Infected cells show keratohyaline granules and intracytoplasmic aggregates
Condyloma Accuminatum
Caused by HPV 6 and 11 (90% of cases)
STD, high risk HPV types (16, 18, 31,33) may increase the risk for cancer
Single or multiple papular lesions that are pearrly filiform, fungating cauliflower, or plaque like
Herpes virus
double stranded DNA herpesvirus, lipid enveloped
Siplex and Varicella zoster
HSV: 1 (common in kids, lips, coldsores, gingivostomatitis)
2 (Afterpuberty genitalia, STI, child abuse)
Lesions: group of clear vesicle which heal without scarring
Varicella Zoster Virus
Chicken pox: Highly contagious and spreads thru respiratory route (incubation time 2 weeks), disease of childhood, rash progresses from macules to vesicles to pustules (all stages are simultaneosly present), complications : Reyes syndrome, pneumonia, self limited cerebelitis
Shingles (HSV): a recurrence of VZV years later, affects 10-20% of population during their lifetime, reactivation of latent VZV infection, increased incidence in elderly and immunocompromised pts, rash has a unilateral dermatomal distribution (thorax and lumber)
herpes virus pathology
HSV and VZV show the same histologic changes, acantholysis of epidermis
Multinucleated keratinocytes with intranuclear inclusions (cowdry Type A inclusion)
Perineurial and intraneurial inflammation
Tzanck Smear
A rapid cytological diagnosis
Make a smear from the base of a freshly opened vescile and staining it with giemsa stain, not as sensitive
Molluscum contagiosum
Cutaneous infection caused by a large brick shaped DNA posvirus
Children acquire infection from close contact eyelids face, axilla
Widespread disease can be seen in HIV pts
highly contagious, self inoculation
Penis vulva and groin STI
Molluscum contagiosum pathology
inverted nodule crater like
Eosinophilic cytoplasmic bodies
Scabies
Arthropod reaction
Contagious causeed by a mite (Sarcoptes scabiei)
Mite transmited thru prolonged direct human contact and rarely by fomites
Extremely pruritic papulovesicular eruption (sometimes burrows)
Fingers, penis, embilicus, waistband, axilla, hands
erupts 4 weeks after infestation
Superficial fungus Dermatophytosis
tinea, common superficial cutaneous infection
Three genera: microsprum, Epidermophyton, Trichophyton
Clinical appearance is variable
Scaly erythematous plaques, often annular, KOH prep rapid test to find the branching septate hyphae
Variations: tinea capitis: t tonsurans Tinea corporis (trunk, T rubrum) Tinea barbae (beard, T verrucosum) Tinea cruris (jock itch, t rubrum and floccosum) Tinea pedis (feet, T rubrum)
