1b// Infections and infestations of the skin Flashcards
What are the pathogens that can cause skin infections and infestations?
bacteria
virus
parasites
fungus
What pathogen causes folliculitis?
bacteria
What is folliculitis?
Follicular erythema; sometimes pustular .
Is folliculitis infectious?
May be infectious or non-infectious.
What is another word for non-infectious folliculitis? And what is it associated with?
Eosinophilic (non-infectious) folliculitis is associated with HIV.
Why may recurrent cases of folliculitis occur?
Recurrent cases may arise from nasal carriage of Staphylococcus aureus, particularly strains expressing Panton- Valentine leukocidin (PVL).
there is a reservoir of staphylococcus in nose and throat
What is the treatment of folliculitis?
Antibiotics (usually flucloxacillin or
erythromycin)
Incision and drainage is required for furunculosis. (progressed folliculitis)
What is the difference between a furuncle and a carbuncle?
A furuncle is a deep follicular abscess
- Involvement with adjacent connected follicles = Carbuncle
What is a carbuncle more likely to lead to than a furnucle?
Carbuncle - more likely to lead to complications such as cellulitis and septicaemia
Why do some people develop recurrent staph impetigo or recurrent furunculosis?
Establishment as a part of the resident microbial flora (in reservoirs)
- Abundant in nasal flora
Immunodeficiency
- Hypogammaglobulinaemia
- Hyper IgE syndrome – deficiency
- Chronic granulomatous disease
- AIDS
- Diabetes Mellitus
What is impetigo?
Impetigo (also called pyoderma) is a superficial bacterial skin infection that is highly contagious. Impetigo can be caused by Streptococcus pyogenes and Staphylococcus aureus.
What does staphylococcus aureus express?
expresses virulence factors that confer pathogenic properties
such as…
- haemolysin
- PVL
- leukocidin
- alpha toxin
What can staphylococcus aureus cause?
ecthyma
impetigo
cellulitis
folliculitis
- furunculosis
- carbuncles
staphylococcal scalded skin syndrome (SSSS)
superinfects other dermatoses (e.g., atopic eczema, HSV, leg ulcers)
What is PVL short for and what does it do?
panton valentine leukocidin
pathogenic factor that leukocyte destruction and tissue (necrosis)
What is Panton Valentine leukocidin
Staphylococcus Aureus (PVL)?
beta pore forming exotoxin
What does PVL increase when it comes to infections?
higher morbidity, mortality, transmissibility
What does PVL Staphylococcus Aureus do and to what on the body?
skin
- recurrent and painful abscesses
- folliculitis
- cellulitis
extracutaneous:
- Necrotising pneumonia
- Necrotising fasciitis
- Purpura fulminans
What is the virulence of Streptococcus?
What increases the risk of acquiring panton valentine leukocidin staphylococcus aureus?
5 Cs
Close Contact – e.g. hugging, contact sports
Contaminated items , e.g. gym equipment, towels or razors.
Crowding –crowded living conditions such as e.g. military accommodation, prisons and boarding schools.
Cleanliness (of environment)
Cuts and grazes – having a cut or graze will allow the bacteria to enter the body
What is the treatment for Panton Valentine Leukocidin Staphylococcus Aureus?
Consult local microbiologist / guidelines
Antibiotics (often tetracycline)
Decolonisation – often:
- Chlorhexidine body wash for 7 days
- Nasal application of mupirocin ointment 5 days)
Treatment of close contacts
What is pseudomonal folliculitis?
What is cellulitis?
Infection of lower dermis and subcutaneous tissue
What happens during cellulitis?
Tender swelling with ill-defined, blanching erythema or oedema
What are most cases of cellulitis caused by?
Most cases: Streptococcus pyogenes & Staphylococcus aureus
What is a predisposing factor of cellulitis?
Oedema is a predisposing factor
What is the treatment for cellulitis?
systemic antibiotics
What is impetigo?
Superficial bacterial infection, stuck-on, honey-coloured crusts overlying an erosion.
What causes impetigo?
- Streptococci
or - Staphylococci
Caused by exfoliative toxins A & B, split epidermis by targeting desmoglein I
What is the impetigo by streptococci?
non-bullous
What is the impetigo by staphylococci?
bullous
What does impetigo often affect?
face (perioral, ears, nares)
How is impetigo treated?
Treated with topical +/- systemic antibiotics.
When does impetiginization occur?
Occurs in atopic dermatitis
- Gold crust
- Staphylococcus aureus
impetiginized eczema
Is lyme disease bacterial or viral?
bacterial
What is another word for lyme disease?
borreliosis
What is borreliosis (lyme disease)?
Annular erythema develops at -
site of the bite of a Borrelia- infected tick
- ring like in the picture
What do the bites from lyme disease form?
ixodes
*most patients don’t remember being bitten
What is the tick infected with in lyme disease?
Borrelia burgdorferi
What is the initial cutaneous manifestation of lyme disease?
Erythema migrans (only in 75%)
- Erythematous papule at the bite site
What does the erythematous papule progress to in lyme disease?
Progression to annular erythema of >20cm
What happens 1-30 days after infection in lyme disease?
fever and headache
Multiple secondary lesions develop - similar but smaller to initial lesion
Neuroborreliosis
- Facial palsy / other CN palsies
- Aseptic meningitis
- Polyradiculitis
Arthritis – painful and swollen large joints (knee is the most affected join)
Carditis
What are the investigations for lyme disease (borreliosis)?
Serology not sensitive
Histopathology - non-specific
High index of suspicion required for diagnosis
treat w/out certainty, bc the risk of progression is worse than rik of antibiotics
Why don’t you perform a biopsy for borreliosis?
bc it’s non specific for lyme disease
Is syphilis bacterial or viral?
bacterial
What is the bacteria that causes syphillis?
Treponema pallidum
What is the primary infection like for syphillis?
Chancre (a single ulcer)
painless ulcer with a firm indurated border
What happens 1 week after the primary chancre in syphillis?
painless regional lymphadenopathy
When does the chancre appear for syphilis?
chancre appears within 10-90 days
What happens if syphilis is left untreated?
Secondary syphilis
When does secondary syphilis begin?
50 days after chancre
What happens during secondary syphilis?
Malaise, fever, headache, pruritus, loss of appetite, iritis
- Rash (88-100%) -Pityriasis rosea-like rash
- Alopecia (‘moth-eaten’)
- Mucous patches
- Lymphadenopathy
- Residual primary chancre
- Condylomata lata
- Hepatosplenomegaly
*‘Great mimicker’ – low threshold for testing
What is a rare manifestation of secondary syphilis?
lues maligna
What is lues maligna?
Pleomorphic skin lesions with pustules, nodules and ulcers with necrotising vasculitis
Where is lues maligna more frequent?
in HIV manifestation
What is tertiary syphilis?
it can destroy nasal cartilage, because it can happen over cartilage destroying it
How do you diagnose syphilis?
● Clinical findings
● Serology
Strong index of suspicion required in 2ndary syphilis
What is the treatment for syphilis?
IM benzylpenicillin or oral tetracycline
What is the only virus you need to know in derm?
herpes simplex virus
What are all the bacterial infections you need to know for derm? (6)
folliculitis
cellulitis
pseudomonal foliculitis
impetigo
Borreliosis (lyme disease)
Syphilis
What is herpes simplex virus?
Primary and recurrent vesicular eruptions
What does herpes favour?
Favour orolabial and genital regions
What I transmission of herpes not limited to?
Transmission can occur even during asymptomatic periods of viral shedding
What are the types of herpes simplex virus, and how can they be transmitted?
● HSV-1 – direct contact with contaminated saliva / other infected secretions
● HSV-2 - sexual contact
Where does herpes replicate?
Replicates at mucocutaneous site of infection
How does herpes simplex virus travel?
Travels by retrograde axonal flow to dorsal root ganglia
travels back down (anterograde) to cause flare ups
When do symptoms of herpes occur?
with 3-7 days of exposure
What happens before the symptoms in herpes?
Preceded by tender lymphadenopathy, malaise, anorexia
± Burning, tingling
What are the symptoms of herpes?
Painful rouped vesicles on erythematous base → ulceration / pustules / erosions with scalloped border
Crusting
Orolabial lesions – often asymptomatic
Genital involvement – often excruciatingly painful→ urinary retention
When does crusting resolve in herpes?
2-6 weeks
What happens when there is reactivation of herpes?
spontaneous, UV, fever, local tissue damage, stress
What are the symptoms of herpes (google)?
Pain or itching around the genitals.
Small bumps or blisters around the genitals, anus or mouth.
Painful ulcers that form when blisters rupture and ooze or bleed.
Scabs that form as the ulcers heal.
Painful urination.
Discharge from the urethra, the tube that releases urine from the body.
Discharge from the vagina.
What are the systemic manifestations of herpes simplex virus?
aseptic meningitis in up to 10% of omen
What is an emergency in herpes?
Eczema herpeticum
- emergency
- Monomorphic,
punched out erosions (excoriated vesicles)
- give IV antivirals (acyclovir)
What happens more in HSV-1 than HSV-2?
What is herpetic whitlow often misdiagnosed as?
paronychia or dactylitis
In who does herpetic whitlow occur most in?
children
What is the danger of giving birth if you have herpes?
Neonatal HSV infection
What happens during neonatal HSV infection?
Exposure to HSV during vaginal delivery – risk higher when HSV acquired near time of delivery
HSV 1 or 2
When does onset of neonatal HSV infection start?
onset from birth to 2 weeks
Where is neonatal HSV infection usually localised?
scalp or trunk
What are the symptoms of neonatal HSV infections?
Vesicles → bullae erosions
What is the mortality like for neonatal HSV infection and what does it require to be treated?
Encephalitis → mortality >50% without treatment, 15% with treatment → neurological deficits
requires IV antivirals
Give an example of where there can be variable manifestations of Herpes?
immunocompromised patients such as HIV or transplant recipients (they have chronic ulcers and wart like lesions)
What is the most common presentation of herpes?
chronic, enlarging ulceration
it can be multiple sites or disseminated
Give examples of how herpes is often atypical?
verrucous, exophytic or pustular lesions
What may herpes start affecting?
Respiratory or GI tracts
How do you diagnose for herpes?
swab for polymerase chain reaction
How do you treat herpes?
Don’t delay
Oral valacyclovir or acyclovir 200mg five times daily in immunocompetent localised infection
- Intravenous 10mg/kg 3 times a day X 7-19 days
How can you classify fungal infections?
superficial
depp/ soft tissue
disseminated
What is an example of a superficial fungal infection?
Pityriasis versicolor
What fungus causes Pityriasis versicolor?
malassezia
What does Pityriasis versicolor cause?
Hypopigmented, hyperpigmented or erythematous macular eruption +/- fine scale
- more noticeable when tanned
When does Pityriasis versicolor begin?
Begins during adolescence (when
sebaceous glands become active)
When are there flares of Pityriasis versicolor?
Flares when temperatures and humidity are high – Immunosuppression
How do you treat pityriasis versicolor?
topical versicolor
What are dermatophytes? And what type of fungal infection do they cause?
fungi that live on keratin
superficial fungal infection
What is are examples of dermatophytes and what do they cause the most of?
Trichophyton rubrum causes the most fungal infections
Trichophyton tonsurans causes the most tinea capitis
What is a kerion?
an inflammatory fungal infection that may mimic a bacterial folliculitis or an abscess of the scalp; scalp is tender and patient usually has posterior cervical lymphadenopathy
What are kerions frequently secondarily infected with?
staphylococcus aureus
What is an Id reaction?
Aka Dermatophytid reactions
Inflammatory reactions at sites distant from the associated dermatophyte infection
What may an Id reaction include?
May include urticaria, hand dermatitis, or erythema nodosum
What is an Id reaction likely secondary to?
likely secondary to a strong host immunologic response against fungal antigens
What is candidiasis?
candida albicans
What do most sites of candidiasis show?
most sites show erythema oedema, thin purulent discharge
What is an example of an opportunistic fungal infection (the only one you need to know)?
Mucormycosis
What is the presentation of mucormycosis?
oedema, then pain, then eschar
What are the symptoms of mucormycosis?
fever, headache proptosis, facial pain, orbital cellulitis ± cranial nerve dysfunction
What are the fungi that can cause Mucormycosis?
Apophysomyces, Mucor, Rhizopus, Absidia, Rhizomucor
What is Mucormycosis associated with?
Diabetes mellitus (1/3 of patients - Diabetic ketoacidosis very high risk)
Malnutrition
Uraemia
Neutropaenia
Medications: Steroids / antibiotics / desferoxamine
Burns
HIV
What is the treatment for Mucormycosis?
aggressive debridement & antifungal therapy amphotericin
What pathogen causes scabies?
parasite
What is scabies?
Contagious infestation caused by Sarcoptes species
How does sarcoptes work for scabies to occur?
Female mates, burrows into upper epidermis, lays her eggs and dies after one month.
What is the onset like for scabies?
Insidious onset of red to flesh-coloured pruritic papules
An insidious disease is any disease that comes on slowly and does not have obvious symptoms at first
What areas of the body does scabies affect?
Affects interdigital areas of digits, volar wrists, axillary areas, genitalia
v itchy
What does scabies look like?
A diagnostic burrow consisting of fine white scale
Crusted or ‘Norwegian’ scabies - hyperkeratosis
often asymptomatic in immunocompromised individuals
How do you treat scabies?
permethrin, oral ivermectin
- Two cycles of treatment are required
What is folliculitis?
inflammation of the hair follicles
How does staphylococcal impetigo manifest on the skin?
as small blisters that burst to leave a yellow, crusty coating
How does borreliosis manifest on the skin?
as a single, expanding red rash often resembling a bull’s-eye
How does HSV infection manifest in new-borns?
as small grouped vesicles on a red base, often accompanied by systemic symptoms
What is the name of the fungus responsible for causing pityriasis versicolor?
malassezia furfur
How does scabies manifest on the skin?
as a fine, red rash accompanied by intense itching, especially at night
