Deep Mycoses

Question 1

Define ‘deep fungal infection’

Answer 1

Any infection below the stratum corneum (in the keratin layer)

Question 2

Are deep mycoses confined to tropical regions?

Answer 2

No! But more common due to
- medical care
- drug availability
- natural infectious sources
- lack of PPE

Question 3

What is the difference in the inflammatory response to a deep fungal infection in the immunocompetent versus immunocompromised?

Answer 3

Immunocompetent
- standard inflammatory response
- granulomatous, neutrophilic microabscesses

Immunocompromised
- anergia response (non-specific, lots of histiocytes)
- florid infection
- often disseminated

Question 4

What is the modality of choice for diagnosis of deep fungal infection?

Answer 4

Fungal culture
Best alternative - histology

Question 5

What is a mycetoma?

Answer 5

A general term for chronic, subcutaneous granulomatous infection with draining sinuses and fistulae

Question 6

What is the difference in the granule colour in actinomyces versus maduromycoses?

Answer 6

Actinomyces - yellow
Maduromycoses - black

Question 7

What is maduromycoses?

Answer 7

“Madura foot”
Was originally used for maduromycoses (madurella species) but now is generalised

Question 8

What are the 3 kinds of mycetoma?

Answer 8

Eumycotic (true fungi)
Actinomycotic (branching bacteria)
Botryomycotic (clump forming bacteria)

Question 9

What is the pathogenesis of mycetoma?

Answer 9

1. Inoculation of causative agent into soft tissue
2. Begins as a small nodule which discharges pus, often with granules
3. Develops slowly via centrifugal extension along the fascial planes
4. Eventually, bony destruction

Question 10

What is the response of mycetoma on microscopy regarding each causative agent?

Answer 10

Uniform response irrespective of agent - neutrophilic micro abscesses

Question 11

What are the features of mycetoma on histology?

Answer 11

Epidermal acanthuses
Parakeratosis
Orthoketatosis
Multinucleate giant cells
Splendore-Hoeppli phenomenon
Peripheral fibrosis

Question 12

Which feature of mycetoma on histology is mistake for SCC?

Answer 12

Orthokeratosis

Question 13

Where do you look for the organisms on histology?

Answer 13

In the micro abscesses

Question 14

What is the Splendore-Hoeppli phenomenon?

Answer 14

Eosinophilic antigen-antibody response around an organism (not specific to fungi)

Question 15

Why does peripheral fibrosis confound therapy of mycetoma?

Answer 15

Causes poor drug penetration

Question 16

Name causative organisms of eumycotic mycetoma

Answer 16

Madurella mycetomi
Allescheria boydii
Phialophera species

Question 17

Name causative organisms of botryomycotic mycetoma

Answer 17

Nocardia brasiliensis
Streptomyces
Actinomyces

Question 18

Name causative organisms of actinomycotic mycetoma

Answer 18

Staph
Strep
E.coli
Proteus
Pseudomonas

Question 19

How is mycetoma distinguished?

Answer 19

Gram
Grocott’s
PAS
ZN

Question 20

Which organism is the most common infective organism of the eumycotic mycetoma group?

Answer 20

Madurella mycetomi

Question 21

Which actinomyces is most common in the actinomycotic group?

Answer 21

Actinomyces israelii

Question 22

Why are pathological changes needed to confirm actinomyces israelii?

Answer 22

Commensal of the mouth and female genital tract

Question 23

What are common sites of actinomycosis?

Answer 23

Cervicofacial
Thoracic
Abdominal
IUCD

Question 24

What are the features of nocardia asteroids?

Answer 24

Delicate
Partially acid fast

Question 25

In which population is nocardiosis more common?

Answer 25

HIV patients

Question 26

What condition of nocardiosis often confused with?

Answer 26

TB

Question 27

What sites does nocardiosis like to infect?

Answer 27

Lung Sinuses Brain Soft tissue Abdomen

Question 28

How do you differentiate actinomyces from nocardia?

Answer 28

Actinomyces - anaerobic - not acid fast - oral and gut Nocardia - aerobic - acid fast - soil exposure

Question 29

What is chromomycosis?

Answer 29

Dermaticeous brown fungi from decaying wood and soil

Question 30

What does chromomycosis look like on histology?

Answer 30

"Stack of pennies" Epidermal hyperplasia

Question 31

Which organisms cause chromomycosis?

Answer 31

Phialophera verrucosa P. pedrosai P. compost P. dermatitis Oladosporiom carionii

Question 32

What is the treatment of chromomycosis

Answer 32

5-flurocytosine Amphotericin B (resistance common)

Question 33

Which organism causes sporotrichosis?

Answer 33

Sporothrix schenckii

Question 34

What is the clinical presentation of sporotrichosis?

Answer 34

Painless nodule at inoculation site with dissemination along the lymphatics

Question 35

Discuss the histological features of sporotrichosis

Answer 35

Small, spherical, cigar-shaped bodies Asteroid bodies Splendore-Hoeppli phenomenon Epidermal hyperplasia Neutrophilic microabscesses

Question 36

How does sporotrichosis present in HIV patients?

Answer 36

Florid infection, easily misdiagnosed Proliferation of intracytoplasmic cigar shaped spores

Question 37

What is the treatment of sporotrichosis?

Answer 37

Potassium iodide

Question 38

How is sporothrix different to cryptosporidium on microscopy?

Answer 38

Sporothrix = mucicarmine negative

Question 39

Which histoplasma capsulatum type is worldwide versus only in Africa?

Answer 39

Worldwide - var capsulatum Africa - var duboisii

Question 40

What is the clinical presentation of histoplasma capsulatum?

Answer 40

Papulonodular lesions of the skin and subcutaneous tissue

Question 41

Which yeast are the spores of histoplasma capsulatum similar to?

Answer 41

Candida granulomatis

Question 42

Which stains are positive for histoplasma capsulatum?

Answer 42

PAS Grocott's H&E (may be refractive)

Question 43

Which type of necrosis is seen in histoplasma capsulatum?

Answer 43

Caseous necrosis (also cryptosporidium)

Question 44

Which site is common for histoplasma capsulatum and why?

Answer 44

Nose - cooler temperature

Question 45

How do you differentiate histoplasma capsulatum from cryptosporidium?

Answer 45

Histoplasma = small and uniform

Question 46

What is a differential diagnosis for histoplasmosis?

Answer 46

Leishmaniasis

Question 47

How is histoplasmosis transmitted?

Answer 47

Inhalation (recreational and occupational)

Question 48

What is the majority of clinical presentations of histoplasmosis?

Answer 48

90% subclinical with spontaneous resolution

Question 49

What are symptomatic presentations of histoplasmosis?

Answer 49

1. Acute pulmonary infection 2. Chronic pulmonary histoplasmosis 3. Disseminated histoplasmosis

Question 50

Discuss the features of acute pulmonary histoplasmosis

Answer 50

Flu-like illness with spontaneous resolution Pancytopenia May extend to mediastinal LN Granulomatous inflammation that mimics TB

Question 51

Discuss the features of chronic pulmonary histoplasmosis

Answer 51

May follow acute pulmonary OR latent lung infection Cavitatory, coin lesions Granulomatous, fibrosing mediastinitis Resembles TB and malignancy Epithelioid histiocytes Caseous necrosis IE HLH

Question 52

Discuss the features of disseminated histoplasmosis

Answer 52

Immunocompromised patients Extensive RES involvement - lymphadenopathy - HSM - BM suppression Oropharynx Papulonodular mucocutaneous lesions that may ulcerate Fever, cough, malaise, headache, weight loss

Question 53

What is the histopathology of histoplasmosis in immunocompetent patients?

Answer 53

Well-formed granulomata Multinucleate giant cells Caseous necrosis Scanty organisms Yeasts easily missed on H&E

Question 54

What is the histopathology of histoplasmosis in immunocompromised patients?

Answer 54

Histiocyte rich infiltrate Numerous small intracellular yeasts Neutrophils Lymphocytes Necrosis variable Dot-like appearance Refractile Narrow-based budding

Question 55

Discuss the features of histoplasma var duboisii

Answer 55

Tendency for caseous and cutaneous involvement Pulmonary disease unusual Long and flat bones Large multinucleate giant cells

Question 56

Which is larger: histoplasma capsulatum var capsulatum or var duboisii?

Answer 56

Var duboisii

Question 57

Which common yeast is mucicarmine positive?

Answer 57

Cryptosporidium

Question 58

In which patient population is mucormycosis most common in?

Answer 58

Diabetic ketoacidosis (rhinocerebral)

Question 59

What is the important feature of mucormycosis on histology?

Answer 59

Broad Non-septate Branch at 45 degrees