derm - infections and infestations Flashcards
what conditions can staph aureus infection cause
ecthyma impetigo cellulitis folliculitis: furunculosis, carbuncles staph scalded skin syndrome superinfects other dermatoses
how does staphylococcus cause infections
expresses virulence factors e.g toxins, haemolysin, leukocidin, peptidoglycan layers etcc that confer pathogenic properties
what virulence does strept possess that leads to infections
strept pyogenes - attaches to epithelial surface via lipoteichoic acid portion of fimbriae
- has m proteins (antiphagocytic) and hylauronic acide capsule
- produces erthrogenic exotoxins
- produces streptolysins S and O
what conditions can strept cause
ecthyma cellulitis impetigo erysipelas scarlet fever necrotising fascitis superinfects other dermatoses
what is folliculitis
follicular erythema - sometimes pustular
can be infectious/non infectious
recurrent cases may arise from nasal carriage of ataph aureus particularly strains expressing pvl
eosinophilic(non infectious) is associated with hiv
what are the treatments for follicultis
antibiotics - usually flucloxacillin or erythromycin
incision and drainage is required for furunculosis
what is difference between furuncle and carbuncle
furuncle = deep follicular abcess carbuncle = composes or furuncles and involves adjacent hair follicles
why do some patients develop recurrent staph impetigo or recurrent furunculosis
have established themselves as part of resident microbial flora (in particular nasal flora) immunodeficiencies : -hypogammaglobulinaemia - chronic granulomatous disease - AIDS - diabetes mellitus
what is panton valnetine leukocidin staph aureus
pvlsa
beta pore forming exotoxin
causes leukocyte destruction and tissue necrosis
= higher morbididity,mortality and transmissibility
in skin: recurrent and painful abcesses, follliculitis and cellulitis
*often painful, more than one site, recurrent, present in contacts
extracutaneous: necrotising pneumonia, necrotising fascitis and purpura fulminans
what are the 5c’s risk of acquiring pvla
close contact e.g hugging, contact sports contaminated items crowding cleanliness cuts and grazes
what is the treatment for pvla
antibiotics - tetracycline
decolonisation e.g chlorhexidine body wash for 7 days
nasal application of mupirocin ointment for 5 days
treatment of close contacts
what is psedomonal follicultis
associated with hot tub use, swimming pools and wet suits
appears 1-3 days after exposure, as diffuse truncal eruption
causes follicular erythematous papule
rarely - abcesses, lyphangitis and fever
most cases self limited - no treatment req
severe/recurrent cases can be treated with oral ciprofloxacin
what is cellulitis
infection of lower dermis and subcut tissue
tender swelling with ill defined,blanching erythema or oedema
most causes = strept pyogenes and staph aureus
oedema = predisposing factor
what is the treatment for cellulitis
systemic antibiotics
what is impetigo
superficial bacterial infection, stuck on honey coloured crusts overlyig an erosion
caused by strepttococci (non bullous) or staph (bullous)
caused by exfoliative toxins a and b, split epidermis by targeting desmoglein 1.
affects face: perioral, ears and
treatment of impetigo
treatment with topical and with or without systemic antibiotics
what is impetiginisation
refers to superficial infections
occurs in atopic dermatitis
typically gold crust and caused by staph aureus
what is ecthyma
severe form of strept impetigo
-thick crust overlying punch out ulceration surrounded by erythema
usually in lower extremities
what is staph scalded skin syndrome
usually in neonates, infants and immunocompromised adults
due to exfoliative toxin
infection occurs at distant site i.e conjunctivitis/abcess
organism cannot be cultured from denuded skin
in neonates - kidneys cannot excrete exfoliative toxin quickly
diffuse tender erythema with rapid progression leads to flaccid bullae, wrinkle and exfoliate leaving oozing erythematous base
clinically resembles sjsten
what is toxic shock syndrome
febrile illness caused by group a staph aureus strain that produces pyrogenic exotoxin tsst1
signs and symptoms of toxic shock syndrome
fever >38.9
hypotension
diffuse erythema
involvement of: gi,muscular,cns,renal and hepatic systems
mucous membranes - erythema
haematological (plts <1000000)
desquamation of palms ans soles 1-2 wks after resolution of erythema
what is erythrasma
infection of corynebacterium minutissiumum
well demarcated patches in interriginous areas
initially pink and becomes brown and scaly
what is pitted keratolysis
pitted erosions of soles
caused by corynebacteria
what is pitted keratolysis treated by
topical clindamycin
what is eryspipeloid
erythema and oedema of hand after handling of raw fish/meat
extends slowly over weeks
caused by erysipelothrix rhusiopathiae
what is anthrax
painless necrotic ulcer with surrounding oedema and regional lymphadenopathy (with pain in lymph nodes) at site of contact with hides, bone meal or wool infected with bacillus antracis
what is blistering distal dactylitis
rare infection caused by strept pyogenes or staph aureus
typically in young children
1/more tender superficial bullae on erythematous base on volar fat pad of a finger
toes may rarely be affected
what is erysipelas
infection of deep dermis and subcutis
casued by beta haemolytic strept or staph aureus
painful
prodrome of malaise,fever and headache
presents as erythematous indurated with sharply demarcated border and cliff drop edge +- blistering
face and limb +- red streak of lymphangitis and local lymphadenopathy
portal of entry must be sought e.g tinea pedis
how is erysipelas treated
with intravenous antibiotics
what is scarlet fever
disease of children
caused by upper rti with erythrogenic toxin producing strept pyogenes
preceded by sore throat,headache, malaise,chills, anorexia and fever
eruption begins 12-48 hrs later
- blanchable tiny pinkish red spots on chest,neck and axillae
- spread to whole body within 12 hrs
- sandpaper like texture
what are some complication of scarlet fever
otitis mastoiditis sinusisitis pneumonia myocarditis hepatitis meningitis rheumatic fever acute glomerulonephritis
what is necrotising fasciitis
initial dusky induration (usually of limb) followed by rapid painful necrosis of skin, connective tissue and muscle
- potentially fatal
usually synergistic: strept,,staph,enterobacteriacae and anaerobes
treatments/diagnosis for necrotising fasciitis
prompt diagnosis essential followed by broad spectrum parenteral antibiotics and surgical debridement
mri can aid diagnosis
blood and tissue cultures determine organisms and sensitivities
mortality is high
can affect scrotum - fourniers gangrene
what is atypical mycobacterial infection
important cause of infection in immunocompromised states
- mycobacterium marinum causes indolent granulomatous ulcers(fish- granuloma) in healthy people, sporotrichoid spread
- mycobacterium chelonae and abcesses - puncture wounds, tattoos, skin trauma or surgery
- mycobacterium ulcerans - important cause of limb ulceration in africa (buruli ulcer) or australia (searles ulcer)
what is borreliosis(lymes disease)
annular erythema develops at site of borrelia infected tick
bite form ixodes tick infected with borrelia burgdorferi
initial cutaneous manifestations - erythema migran - only 75%
- erythematous papule at bite site
- progression to annular erythema of >20cm
what can occur 1-30 days after infection, fever and headache in lyme disease
multiple secondary lesions develop - similar but smaller to initial lesions
- neuroborreliosis: facial palsy/other cn palsies, asesptic meningitis, polyradiculitis
- arthritis - painful and swollen large joints
- carditis
how to diagnose lyme disease
serology not sensitive and histology is non specific therefore high index of suspicion is used to make diagnosis and based of clinical features
what is tularaemia
caused by francesella tularensis
acquired through: handling infected animals,tick bites and deerfly bites
- ulceroglandular form
- primary skin lesions is small papules at innoculation site that rapidly necrosis leading to painful ulceration
+- local cellulitis
painful regional lymphadenopathy
what are the systemic features of tularaemia
fever, chills, headache and malaise
what is ecthyma gangrenosum
pseudomonas aeruginosa
usually occurs in neutropaenic patients
red macules - oedematous - haemorrhagic bullae
- may ulcerate in late stages/form eschar surrounded by erythema
what is syphilis
caused by treponema pallidum
primary infection chancre - painless ulcer with firm indurated border
painless regional lymphadenopathy one week after primary chancre
chancre appears within 10-90 days
what is secondary syphilis
begins 50 days after chancre skin manifestations: pityriasis rosea like rash allopecia mucous patches lymphademopathy residual primary chancre condylomata lata hepatosplenomegaly
symptoms of secondary syphilis
systemic symptoms
malaise fever headache pruritus loss of appetite iritis
what is lues maligna
rare manifestation of secondary syphilis
pleomorphic skin lesions with pustules,nodules and ulcers with necrotising vasculitis
more frequent in hiv maifestations
what is tertiary syphilis
glumma skin lesions - nodules and plaques
extend peripherally while central areas heal with scarring and atrophy
mucosal lesions extend to and destroy nasal cartilage
can also develop cvd and neurosyphilis
how to diagnose syphilis
clinical findings
serology
strong index of suspicion required in secondary syphilis
what is the treatment for syphilis
im benzylpenicillin or oral tetracycline
what is leprosy
caused by mycobacterium leprae
obligate intracellular bacteria - predominantly affects skin and nerves but can affect any organ
what is the difference between lepromatous leprosy and tuberculoid leprosy
lepromatous :
- multiple lesions: macules,papules and nodules
sensation and sweating normal early on
tuberculoid: solitary or few lesions with elavated borders, atrophic center sometimes annular
hairless,anhidrotic,numb
what is tuberculosis
can affect any organ incl skin
only 5-10% lead to clinical disease
caused by mycobacterium tuberculosis
how can cutaneous tuberculosis be acquired
exogenously - primary innoculation tb and tuberculosis verrucosa cutis
contigous endogenous spread - scrofulderma or autoinnoculation can develop into periorificial tuberculosis
haematogenous/lymphatic endogenous spread - dissemination( lupus vulgaris, miliary tb, gummas)
what are the investigations for tuberculosis
interferon gamma release assay
histology - zn stain
culture/pcr
what is tuberculous chancre
- painless, firm, reddish brown papulonodule that forms ulcer
what is tuberculosis verrucosa cutis
wart like papule that evolves to form redbrown plaque
what is scrofulderma
subcutaneous nodule with necrotic material - becomes fluctuant and drains, with ulceration and sinus tract formation
what is orificial tb
non healing ulcer of nasal mucosa that is painful
what is lupus vulgaris
red brown plaque +- central scarring and ulceration
what is miliary tb
pinhead sized, bluish red papules capped by minute vesicles
what is tuberculous gumma
firm subcutaneous nodules, later ulcerates
what is molluscum cantagiosum
poxvirus infection
common in children and immunocompromised
usually resolves spontaneously
what is the differential diagnosis for molluscum contagiosum
verrucae
condyloma acuminata
basal cell carcinoma
pyogenic granuloma
what are the treatment options for molluscum contagiosum
curettage
imiquimod
cidofovir
what is herpes simplex virus
primary and recurrent vesicular eruptions
favour orolabial and genital regions
transmission can occur even during asymptomatic periods of viral shedding
how does hsv 1 spread
direct contact with contaminated saliva/ other oral secretions
virus replicates at mucocutaneous site of infection
travels by retrograde axonal flow to dorsal root ganglia
how does hs2 spread
sexual contact
what are the symptoms of hsv
symptoms occur within 3-7 days of exposure
preceded by tender lymphadenopathy, malaise, anorexia +- burning and tingling
painful rouped vesicles on erythematous base -> ulceration/pustules/erosions with scalloped border
crusting and resolution within 2-6 weeks
orolabial lesions - often asymptomatic
genital involvement - often excruciatingly painful -> urinary infection
systemic manifestations - aseptic meningitis in upto 10% of women
reactivation - spontaneous, uv, fever, local tissue damage, stress
what is eczema herpeticum
emergency
monomorphic punched out erosions - excoriated vesicles
how is eczema herpeticum treated
intravenous acyclovir accompanies by antibiotics for superinfections with staph aureus or strept
whatis hepatic whitlow
hsv 1>2 infection of digits - pain swelling and vesicles
misdiagnosed as paronychia or dactylitis
often in children
what is hepres gladiatorum
hsv1 involvment of cutaneous site reflecting sites of contact with another athletes lesion
contact sports e.g wrestling
what is neonatal hsv infection
exposure to hsv during vaginal delivery - risk higher when hsv acquired near time of delivery
hsv1/2
onset from birth to 2 wks
locally usually - on scalp/trunk
vesicles - bullae erosions
encephalitis - mortality >50% without treatment, 15% with treatment, can lead to neurological deficits
how to treat neonatal hsv
requires iv antivirals
what is severe/chronic hsv
immunocompromised patients e.g hiv/transplant recipients
most common presentation - chronic enlarging ulceration
often atypical e.g verrucous, exophytic or pustular lesions
involvement of resp/gi tract can occur
how to diagnose for hsv
swab for polymerase chain reaction
what is treatment for hsv
dont delay!
oral valacyclovir/acyclovir 200mg 5 times daily in immunocimpetent localised infections
intravenous 10mg/kg tds
what is varicella zoster virus
is dermatomal disease
can affect singledermatomes or multidermatomal
what is hand foot and mouth disease
caused by coxackie a16, echo71
an acute self limiting coxsackievirus infection
prodrome of fever, malaise and sore throat
spread by direct contact via oral oral route and oral faecal route
how does hand foot and mouth disease present
red macules, vesicles and ulcers develop on buccal mucosa, tongue,palate and pharynx - may also develop on hand and feet
what viruses cause morbilliform( measle like) eruptions
measles rubella ebv cmv hhv6 hhv7 leptospirosis rickettsia
what causes petechial/purpura infestations
coagulation abnormalities
vasculitis
infections
viruses - hep b, cmv, rubella, yellow fever, dengue fever, west nile virus
bacterial - borrelia, rickettsia, neisseria,endocarditis
other: plasmodium falciparum, trichnella,ten,ergot poisoning raynauds
what is giannoti crosti syndrome
papular acrodermatitis of childhood
viral eruption that causes acute symmetrical erythematous papular eruption on face,extremities and buttocks - usually age 1-3 yrs
what are the causes of gianotti crosti syndrome
ebv - most common cmv hhv6 coxsackie virus a16,b4,b5 hep b
what is erythema infectiosum
parovirus b19
initially mild fever and headache
few days later = slapped cheeks for 2-4 days
ten reticulated rash of chest and thighs in 2nd stage
what is roseola infantum
aka exanthem subitum aka 6th disease common in children 2-5 days high fever followed by appearance of small pale pink papules on trunk and head last hrs to 2 days caused by hhv6 and hhv7
what is orf
Caused by parapoxvirus
direct exposure to sheep or goats
dome shaped, firm bullae that develop umbilicated crust
usually develop on hands and forearms
generally resolve without therapy in 4-6 wks
what are warts
caused by 200 subtypes of hpv
what are superficial fungal infections caused by
pity:
hypopigmented, hyperpigmented or erythematous macular eruption +- fine scale
caused by malassezia spp
begins during adolescence when sabaceous glands become active
flares when temperatures and humidity are high - immunosuppression
what are superficial fungal infections treated with
topical azole
what are dermatophytes
fungi that live on keratin
what causes the most fungal infections
trichophytan tonsurans
what is kerion
an inflammatory fungal infection that may mimic a bacterial folliculitis or an abscess of scalp.
scalp is tender and patient usually has posterior cervical lymphadenopathy
- frequently secondarily infected with staph aureus
what is tinea pedis
trichophyton rubrum - scaling and hyperkeratosis of plantar surface of food trichophyton mentagrophytes( interdigitale) - sometimes vesiculobullous reaction on arch/side of foot
what is an id infection
aka dermatophytid reaction
inflammatory reactions at sites distant from associated dermatophyte infection
may include urticaria, hand dermatitis or erythema nodosum
likely secondary to host immunologic response against fungal antigens
what us majocchi granuloma
follicular abscess produced when dermatophyte infection penetrates follicular wall into surrounding dermis: tender
trichophyton rubrum/ mentagrophytes are usually culprit
what is candidiasis
caused by candida albicans
predisposed by occlusion, moisture, warm temp, diabetes m
most sites show erythema oedema, thin purulent discharge
usually an intertriginous infection (affecting axillae, submammary folds, cururae and digital clefts) or of oral mucosa
common cause of vulvovaginitis
may affect mucosae
can be systemic - immunocompromise
what are deep fungal infections
capacity for deep invasion of skin or production of skin lesions secondary to systemic visceral infection subcutaneous fungal infections - infections of implantations (inoculation) - sporotrichosis - phaeohypomycosis - chromomycosis - mycetoma - lobomycosis - rhinospordiosis
what do systemic resp endemic fungal infections include
blastomycosis histoplasmosis coccidiomycosis paracoccidoiomycosis penicillinosis disease in both immunocompetent and immunosupressed
what is a risk factor for aspergillosis
neutropaenia and corticosteroid therapy
what is aspergillosis
primarily resp pathogen
cutaneous lesions being well circumscribed papule with necrotic base and surrounding erythematous halo
propensity to invade blood vessels causing thrombosis and infarction
lesions destructive - may extend into cartilage, bone and fascial planes
should be considered in differential of necrotising lesions
fusarium causes similar illness and cutaneous lesions both clinically and histologically
what is presentation of mucormycosis
fever, headache, facial oedema, proptosis, facial pain, orbital cellulitis +- cranial nerve dysfunction
what can mucormycosis be caused by
apophysomyces, mucor, rhizopus, absidia, rhizomucor
what are the associations with mucormycosis
diabetes mellitus malnutrition neutropenia meds: steroids/antibiotics/desferoxamine burns hiv
what is the treatment for mucormycosis
aggressive debridement and antifungal therapy
- culture positive in only 30% of cases
what are scabies
contagious infestations caused by sarcoptes species
female mates, burrows into upper epidermis, lays eggs and dies after one month
affects interdigital areas of digits, volar wrists, axillary areas, genitalia
what is hyperkeratosis
crusted/norwegian scabies
often asymptomatic - found in immunocompromised individuals
what is the treatment for scabies
permethrin
oral ivermectin
- 2 cycles of treatment are required
what are head louse
pediculus humanus capitis
entire life cycle spent in haor
secondary infection common
what is the treatment for head louse
malathion
permethrin
oral ivermectin
what is body louse
pediculus humanus corporis
lives and reproduces in clothing - lives to feed, rarely found on skin
- pruritic papules and hyperpigmentation
- found in overcrowding, poverty and poor hygiene
- eliminated by thorough cleaning/discarding clothes
what is pubic louse
phithrus pubis aka crabs - 3 pairs of legs
eggs found on hair shaft, also found in occipital scalp, body hair, eyebrow and eyelash, axillary hair
what is the treatment for pubic louse
malathion/permethrin
oral ivermectin
what are bedbugs
climex lectularis - reddish browb, wingless insect
itch weals around central punctum
