Deep Mycoses Flashcards
Define ‘deep fungal infection’
Any infection below the stratum corneum (in the keratin layer)
Are deep mycoses confined to tropical regions?
No! But more common due to
- medical care
- drug availability
- natural infectious sources
- lack of PPE
What is the difference in the inflammatory response to a deep fungal infection in the immunocompetent versus immunocompromised?
Immunocompetent
- standard inflammatory response
- granulomatous, neutrophilic microabscesses
Immunocompromised
- anergia response (non-specific, lots of histiocytes)
- florid infection
- often disseminated
What is the modality of choice for diagnosis of deep fungal infection?
Fungal culture
Best alternative - histology
What is a mycetoma?
A general term for chronic, subcutaneous granulomatous infection with draining sinuses and fistulae
What is the difference in the granule colour in actinomyces versus maduromycoses?
Actinomyces - yellow
Maduromycoses - black
What is maduromycoses?
“Madura foot”
Was originally used for maduromycoses (madurella species) but now is generalised
What are the 3 kinds of mycetoma?
Eumycotic (true fungi)
Actinomycotic (branching bacteria)
Botryomycotic (clump forming bacteria)
What is the pathogenesis of mycetoma?
- Inoculation of causative agent into soft tissue
- Begins as a small nodule which discharges pus, often with granules
- Develops slowly via centrifugal extension along the fascial planes
- Eventually, bony destruction
What is the response of mycetoma on microscopy regarding each causative agent?
Uniform response irrespective of agent - neutrophilic micro abscesses
What are the features of mycetoma on histology?
Epidermal acanthuses
Parakeratosis
Orthoketatosis
Multinucleate giant cells
Splendore-Hoeppli phenomenon
Peripheral fibrosis
Which feature of mycetoma on histology is mistake for SCC?
Orthokeratosis
Where do you look for the organisms on histology?
In the micro abscesses
What is the Splendore-Hoeppli phenomenon?
Eosinophilic antigen-antibody response around an organism (not specific to fungi)
Why does peripheral fibrosis confound therapy of mycetoma?
Causes poor drug penetration
Name causative organisms of eumycotic mycetoma
Madurella mycetomi
Allescheria boydii
Phialophera species
Name causative organisms of botryomycotic mycetoma
Nocardia brasiliensis
Streptomyces
Actinomyces
Name causative organisms of actinomycotic mycetoma
Staph
Strep
E.coli
Proteus
Pseudomonas
How is mycetoma distinguished?
Gram
Grocott’s
PAS
ZN
Which organism is the most common infective organism of the eumycotic mycetoma group?
Madurella mycetomi
Which actinomyces is most common in the actinomycotic group?
Actinomyces israelii
Why are pathological changes needed to confirm actinomyces israelii?
Commensal of the mouth and female genital tract
What are common sites of actinomycosis?
Cervicofacial
Thoracic
Abdominal
IUCD
What are the features of nocardia asteroids?
Delicate
Partially acid fast
In which population is nocardiosis more common?
HIV patients
What condition of nocardiosis often confused with?
TB
What sites does nocardiosis like to infect?
Lung
Sinuses
Brain
Soft tissue
Abdomen
How do you differentiate actinomyces from nocardia?
Actinomyces
- anaerobic
- not acid fast
- oral and gut
Nocardia
- aerobic
- acid fast
- soil exposure
What is chromomycosis?
Dermaticeous brown fungi from decaying wood and soil
What does chromomycosis look like on histology?
“Stack of pennies”
Epidermal hyperplasia
Which organisms cause chromomycosis?
Phialophera verrucosa
P. pedrosai
P. compost
P. dermatitis
Oladosporiom carionii
What is the treatment of chromomycosis
5-flurocytosine
Amphotericin B (resistance common)
Which organism causes sporotrichosis?
Sporothrix schenckii
What is the clinical presentation of sporotrichosis?
Painless nodule at inoculation site with dissemination along the lymphatics
Discuss the histological features of sporotrichosis
Small, spherical, cigar-shaped bodies
Asteroid bodies
Splendore-Hoeppli phenomenon
Epidermal hyperplasia
Neutrophilic microabscesses
How does sporotrichosis present in HIV patients?
Florid infection, easily misdiagnosed
Proliferation of intracytoplasmic cigar shaped spores
What is the treatment of sporotrichosis?
Potassium iodide
How is sporothrix different to cryptosporidium on microscopy?
Sporothrix = mucicarmine negative
Which histoplasma capsulatum type is worldwide versus only in Africa?
Worldwide - var capsulatum
Africa - var duboisii
What is the clinical presentation of histoplasma capsulatum?
Papulonodular lesions of the skin and subcutaneous tissue
Which yeast are the spores of histoplasma capsulatum similar to?
Candida granulomatis
Which stains are positive for histoplasma capsulatum?
PAS
Grocott’s
H&E (may be refractive)
Which type of necrosis is seen in histoplasma capsulatum?
Caseous necrosis (also cryptosporidium)
Which site is common for histoplasma capsulatum and why?
Nose - cooler temperature
How do you differentiate histoplasma capsulatum from cryptosporidium?
Histoplasma = small and uniform
What is a differential diagnosis for histoplasmosis?
Leishmaniasis
How is histoplasmosis transmitted?
Inhalation (recreational and occupational)
What is the majority of clinical presentations of histoplasmosis?
90% subclinical with spontaneous resolution
What are symptomatic presentations of histoplasmosis?
- Acute pulmonary infection
- Chronic pulmonary histoplasmosis
- Disseminated histoplasmosis
Discuss the features of acute pulmonary histoplasmosis
Flu-like illness with spontaneous resolution
Pancytopenia
May extend to mediastinal LN
Granulomatous inflammation that mimics TB
Discuss the features of chronic pulmonary histoplasmosis
May follow acute pulmonary OR latent lung infection
Cavitatory, coin lesions
Granulomatous, fibrosing mediastinitis
Resembles TB and malignancy
Epithelioid histiocytes
Caseous necrosis
IE
HLH
Discuss the features of disseminated histoplasmosis
Immunocompromised patients
Extensive RES involvement
- lymphadenopathy
- HSM
- BM suppression
Oropharynx
Papulonodular mucocutaneous lesions that may ulcerate
Fever, cough, malaise, headache, weight loss
What is the histopathology of histoplasmosis in immunocompetent patients?
Well-formed granulomata
Multinucleate giant cells
Caseous necrosis
Scanty organisms
Yeasts easily missed on H&E
What is the histopathology of histoplasmosis in immunocompromised patients?
Histiocyte rich infiltrate
Numerous small intracellular yeasts
Neutrophils
Lymphocytes
Necrosis variable
Dot-like appearance
Refractile
Narrow-based budding
Discuss the features of histoplasma var duboisii
Tendency for caseous and cutaneous involvement
Pulmonary disease unusual
Long and flat bones
Large multinucleate giant cells
Which is larger: histoplasma capsulatum var capsulatum or var duboisii?
Var duboisii
Which common yeast is mucicarmine positive?
Cryptosporidium
In which patient population is mucormycosis most common in?
Diabetic ketoacidosis (rhinocerebral)
What is the important feature of mucormycosis on histology?
Broad
Non-septate
Branch at 45 degrees
