Common skin infections Flashcards
Which pathogen causes cold sores?
Herpes Simplex
(HSV-1, HSV-2)
Where does HSV-1 most commonly affect?
orofacial
Where does HSV-2 most commonly affect?
genital
How is Herpes simplex virus transmitted?
direct contact at a mucosal surface or on sites of abraded skin
Describe Herpes simplex lesions
grouped vesicles on erythematous base
crust and erosions form
painful
Genital Herpes simplex treatment
topical acyclovir 5% ointment (can use systemic acyclovir)
HSV prognosis
persists in sensory ganglia for life
tends to recur
HSV complications
erythema multiforme
eczema herpeticum
affect CNS
What causes shingles (Herpes zoster)?
Varicella zoster virus
How is shingles transmitted?
reactivation of latent VZV in sensory ganglia (previously had chicken pox)
Shingles symptoms and signs
pain in dermatomal or band-like pattern
followed by grouped vesicles on erythematous base
crusting
fever
malaise
can involve the eyes (ophthalmology referral needed)
How is Herpes zoster treated?
analgesics
acyclovir (needs to be within 24-72 hours of disease onset)
Herpes zoster complications
post-herpetic neuralgia
cranial nerve syndromes (eg. Ramset hunt syndrome)
What causes viral warts?
human papillomavirus (HPV)
Define viral warts
benign epithelial growths
Which HPV subtypes can cause cancers?
16 and 18 are most common (cervical cancer)
Describe a wart
hyperkeratotic flesh-coloured papule and/or plaque studded with small black dots (thrombosed capillaries)
Proper name for verrucae?
plantar warts
Warts treatment
no treatment
topical salicylic acid with paring
duct tape
cryosurgery
What causes molluscum contagiosum?
molluscum contagiosum virus (MCV) (poxvirus)
Describe molluscum contagiosum
benign self-limited papular eruption
often look like pearly papules
smooth flesh-coloured, dome-shaped, umbilicated papules
contain keratotic (cheesy) plug
Transmission of molluscum contagiosum
skin-to-skin contact
Which pathogens cause impetigo?
staphylococcus aureus > streptococcus pyogenes
Describe non-bullous impetigo
vesicles or pustules on erythematous skin –> erosions –> golden yellow crust
Describe bullous impetigo
flaccid bullae with clear yellow fluid (S.Aureus) –> erosions –> golden yellow crust
Bullous impetigo treatment
topical and/or systemic antibiotics (topical = mupirocin, systemic = beta lactams eg. penicillins)
Which pathogens cause folliculitis/furunculosis/carbunculosis?
Staphylococcus aureus
Pseudomonas aeruginosa
Describe folliculitis
follicular pustules
Describe furunculosis
tender, erythematous, fluctuant nodules that rupture with purulent discharge
Describe carbunculosis
larger and deeper inflammatory nodules often with purulent drainage (larger than furuncles)
Furunculosis/carbunculosis treatment
topical treatment 1% clindamycin or 2% erythromycin
systemic antistaphylococcal antibiotics
incision + drainage
Which pathogens cause ecthyma?
Staphylococcus aureus
Streptococcus pyogenes
Describe ecthyma
vesicles and bullae that progress to punched-out ulcerations with adherent crust which heals with scarring
often dark centre
Ecthyma diagnosis
clinical presentation
confirmation by culture
Ecthyma treatment
oral antistaphylococcal antibiotics
Which pathogens cause erysipelas and cellulitis?
Staphylococcus aureus
Streptococcus pyogenes
Difference between erysipelas and cellulitis?
cellulitis affects deeper layers of skin
How do you monitor if antibiotics are working in erysipelas and cellulitis?
draw around erythematous areas
area should shrink if antibiotics working
Describe erysipelas
tender, well-defined erythematous patch
Erysipelas and cellulitis treatment
beta lactam antibiotics
Describe cellulitis
ill-defined erythematous and edematous patch
Which pathogens cause necrotising fasciitis?
Streptococcus pyogenes
Group B and C streptococci
Vibrio vulnificus
Clostridium perfringens
Bacteroides fragilis
(mixed infections common)
What is necrotising fasciitis?
infection of subcutaneous tissue and fascia
Transmission necrotising fasciitis
after injury
idiopathic
Describe necrotising fasciitis + symptoms
erythema
pain
extends to deep underlying fascia
skin becomes dusky and bullae forms followed by necrosis, gangrene
rapid progress
fever
systemic toxicity, organ failure, shock, death
Necrotising fasciitis treatment
biopsy for histology
gram stain and culture to identify pathogen
Necrotising fasciitis treatment
surgical debridement or amputation
antibiotics (gentamicin, clindamycin)
Which pathogen causes scabies?
Sarcoptes scabiei var.hominis (human itch mite)
What is scabies?
infectious disease of skin causes by S.scabiei burrowing into epidermis
Scabies symptoms
itching (especially at night)
Describe scabies
burrows, vesicles, papules and pustules
common in finger webs
How is scabies diagnosed?
looking for mites
look for eggs under microscope (skin scrapings)
Scabies treatment
skin lotions containing permethrin
all family members
all over body
repeat treatment in 7 days (as more eggs may have hatched)
What are the 3 subtypes of leishmaniasis?
Cutaneous leishmaniasis
Mucocutaneous leishmaniasis
Diffuse cutaneous leishmaniasis
Which pathogens cause each subtype of leishmaniasis?
CL = leishmania tropica
MCL = leishmania braziliensis
DCL = leishmania mexicana, leishmania aethiopia
Cutaneous leishmaniasis symptoms
skin lesions with erythema, inflammation and ulceration
Mucocutaneous leishmaniasis symptoms
lesions of nasal and/or oral mucosa
Diffuse cutaneous leishmaniasis symptoms
multiple deep skin lesions
Transmission of mucocutaneous leishmaniasis
bites of infected sandflies
Leishmaniasis treatment by subtype
CL = self-healing, antibiotics
MCL, DCL = pentavalent antimony, amphotericin B
What pathogen causes cutaneous larva migrans (creeping eruption)?
larva of dog and cat hookworm (Ancylostoma braziliensis)
What is cutaneous larva migrans?
cutaneous eruption usually confined to skin of feet, arms or buttocks caused by migrating larva
Transmission of cutaneous larva migrans
active penetration of the skin by larva
Cutaneous larva migrans symptoms
erythematous, pruritic, serpiginous (wavy margin) lesions that advance several mm/day
Cutaneous larva migrans treatment
thiabendazole (topical or oral)
albendazole
mebendazole
ivermectin
antibiotics
What is tinea?
fungal infection of skin
usually peripheral scaling discoid lesions
How is tinea diagnosed?
skin scrapings
direct microscopy (may see branching hyphae)
woods light = green fluorescence
Tinea main symptom
itch
Tinea treatment
topical antifungals (imidazoles)
systemic antifungals for nails, scalp, widespread or chronic infections
Which tinea subtype affects the body?
Tinea Corporis
Which tinea subtype affects the head?
Tinea Capitis
Which tinea subtype affects the feet?
Tinea Pedis
Which tinea subtype affects the groin?
Tinea Cruris
What causes candidal intertrigo?
yeast - usually candida albicans
What is candidal intertrigo?
superficial mycotic infection of skin
tend to affect moist occluded skin folds
Describe candidal intertrigo
erythematous macerated patch with satellite macules or pustules extending beyond the flexure
Candidal intertrigo diagnosis
skin scrapings or swab
Which 2 conditions can predispose someone to candidal intertrigo?
Diabetes mellitus
HIV
Candidal intertrigo treatment
topical antifungals (eg. clotrimazole)
or antifungal with weak steroid (eg. daktacort)
keep area dry (eg. lose weight, loose clothing)
oral antifungals if severe (eg fluconazole)
What causes pityriais versicolor?
yeast - Malassezia furfur
What is pityriasis versicolor?
superficial mycotic infection of skin
Describe pityriasis versicolor
confluent, fine, scaly, well-demarcated, hypo/hyper-pigmented plaques
Pityriasis versicolor diagnosis
skin scrapings or swab
Pityriasis versicolor treatment
selenium sulfide shampoo
ketoconazole shampoo
topical antifungals
