Skin infestations and infections 2 Flashcards
What is the initial presentation of necrotising fasciitis?
dusky induration (usually of a limb), followed by rapid painful necrosis of skin, connective tissue and muscle
What is necrotising fasciitis caused by?
- Potentially fatal
* Usually synergistic: streptococci, staphylococci, enterobacteriaceae and anaerobes
What is in the diagnosis and treatment of necrotising fasciitis?
- Prompt diagnosis essential (requires high index of suspicion), followed by broad-spectrum parenteral antibiotics and surgical debridement
- MRI can aid diagnosis.
- Blood and tissue cultures can determine organisms and sensitivities.
- Mortality is high.
What is it called when necrotising fasciitis affects the scrotum?
Fournier’s gangrene
What is atypical mycobacterial infection?
Important cause of infection in immunosuppressed states
What do mycobacterium marinum cause?
- indolent granulomatous ulcers (fish-tank granuloma) in healthy people
- Sporotrichoid spread
What does myobacterium choelonae and abscessus come from?
puncture wounds, tattoos, skin trauma or surgery
What does myobacterium ulcerans cause?
limb ulceration in Africa (Buruli ulcer) or Australia (Searle’s ulcer)
Where does annular erythema develop (borreliosis lyme disease)?
at site of the bite of a Borrelia-infected tick
What does the bite form in lyme disease?
Ixodes tick infected with Borrelia burgdorferi
What are the intial cutaneous manifestations in lyme disease?
- Erythema migrans (only in 75%)
- Erythematous papule at the bite site
- Progression to annular erythema of >20cm
What are the other manifestations of lyme disease?
- 1-30 days after infection, fever, headache
- Multiple secondary lesions develop - similar but smaller to initial lesion
- Neuroborreliosis
- Arthritis – painful and swollen large joints (knee is the most affected join)
- Carditis
What happens in neuroborreliosis?
- Facial palsy / other CN palsies
- Aseptic meningitis
- Polyradiculitis
What is the serology and histopathology like in lyme disease?
- Serology not sensitive
- Histopathology - non-specific
- High index of suspicion required for diagnosis
What is tularaemia caused by?
Francisella tularensis
What is tularaemia aquired through?
- Handling infected animals (squirrels and rabbits)
- Tick bites
- Deerfly bites
What is the form of tularaemia?
Ulceroglandular form
What are the symptoms of tularaemia?
- Primary skin lesion is small papules at inoculation site that rapidly necroses – leading to painful ulceration
- +/- local cellulitis
- Painful regional lymphadenopathy
What are systemic symptoms of tularaemia?
fever, chills, headache and malaise
What is another word for ecthyma gangrenosum?
Pseudomonas aeruginosa
When does ecthyma gangrenosum occur?
neutropaenic patients
What does ecthyma gangrenosum look like?
- Red macule(s) to oedematous to haemorrhagic bullae.
2. May ulcerate in late stages or form an eschar surrounded by erythema
When organisms can cause a similar appearance to escharotic lesions?
- Pseudomonas
- Aspergillosis
- Leishmaniasis
- Cryptococcosis
- Lues maligna
- Rickettsial infections
- Cutaneous anthrax
- Tularaemia
- Necrotic arachnidism (brown recluse spider bite)
- Scrub typhus (Orientia tsutsugamushi)
- Rat bite fever (Spirillum minus)
- Staphylococcal or streptococcal
- Ecthyma
- Lyme disease
What is another name for syphilis?
Treponema pallidum
What is the primary infection chancre in syphilis?
painless ulcer with a firm indurated border
What happens one week after the primary chancre in syphilis?
- Painless regional lymphadenopathy one week after the primary chancre
- Chancre appears within 10-90 days
When does secondary syphilis begin?
50 days after chancre
What are the symptoms of secondary syphilis?
Malaise, fever, headache, pruritus, loss of appetite, iritis
Why is syphilis a great mimicker?
– low threshold for testing - Rash (88-100%) -Pityriasis rosea-like rash - Alopecia (‘moth-eaten’) - Mucous patches - Lymphadenopathy - Residual primary chancre - Condylomata lata - Hepatosplenomegaly
What is lues maligna?
Rare manifestation of secondary syphilis
What happens in lues maligna?
Pleomorphic skin lesions with pustules, nodules and ulcers with necrotising vasculitis
When is lues maligna more frequent?
HIV manifestation
What happens in tertiary syphilis?
- Gumma Skin lesions - nodules and plaques
- Extend peripherally while central areas heal with scarring and atrophy
- Mucosal lesions extend to and destroy the nasal cartilage
- Cardiovascular disease
- Neurosyphilis (general paresis or tabes dorsalis)
What is involved in the diagnosis of syphilis?
- Clinical findings
- Serology
- Strong index of suspicion required in 2ndary syphilis
What is the treatment of syphilis?
IM benzylpenicillin or oral tetracycline
What is the name for leprosy?
Mycobacterium leprae
What does leprosy affect?
- Obligate intracellular bacteria -predominantly affects skin & nerves, but can affect any organ
- Clinical spectrum
What happens in lepromatous leprosy?
- Multiple lesions: macules, papules, nodules
2. Sensation and sweating normal (early on)
What happens in tuberculoid leprosy?
- Solitary or few: elevated borders – atrophic center, sometimes annular
- Hairless, anhidrotic, numb
What can TB affect?
- any organ system, including the skin
- 5-10% of infections lead to clinical disease
How can cutaneous TB be acquired?
- Exogenously (primary-inoculation TB and tuberculosis verrucosa cutis)
- Contiguous endogenous spread – (scrofuloderma )or autoinoculation – periorificial tuberculosis
- Haematogenous/lymphatic endogenous spread –dissemination (lupus vulgaris, miliary
tuberculosis, gummas
What are the investigations for TB?
- Interferon-γ release assay (Quantiferon-TB)
- Histology – ZN stain
- Culture / PCR
What are the cutaneous manifestations of TB?
- Tuberculous chancre
- Tuberculosis verrucosa cutis
- Scrofuloderma
- Orificial TB
- Lupus vulgaris
- Miliary TB -
- Tuberculous gumma
What is TB chancre?
painless, firm, reddish-brown papulonodule that forms an ulcer
What is TB verrucosa cutis?
wart-like papule that evolves to form redbrown plaque
What is scrofuloderma?
subcutaneous nodule with necrotic material - becomes fluctuant and drains, with ulceration and sinus tract formation
What is orificial TB?
non-healing ulcer of the nasal mucosa that is painful
What us lupus vulgaris?
red brown plaque - +/- central scarring, ulceration
What is milary TB?
pinhead-sized, bluish-red papules capped by minute vesicles
What is TB gumma?
firm subcutaneous nodule - later ulcerates
What is molluscum contagiosum?
Poxvirus infection
When is molluscum contagiosum common?
children and immunocompromised
What are the differential diagnosis of molluscum contagiosum?
- Verrucae
- Condyloma acuminata
- Basal cell carcinoma
- Pyogenic granuloma
What are the treatment options for molluscum contagiosum?
●Usually resolve spontaneously ●Treatment options -curettage -imiquimod -cidofovir
