Systemic Mycoses

Question 1

What is the definition of systemic mycoses?

Answer 1

Fungi that can cause pneumonia and disseminate throughout the body.

Question 2

What are the primary fungal pathogens that are important to know?

Answer 2

• Histoplasma capsulatum
• Blastomyces dermatitidis
• Coccidioides

Question 3

found in soil, bird, and bat droppings

Answer 3

histoplasmosis

Question 4

What are the clinical manifestations of histoplasmosis?

Answer 4

• Asymptomatic for low-intensity exposure
• Pulmonary (infiltrates, mediastinal lymphadenopathy, TB-like illness, progression to cavitating lesions)
• Disseminated (febrile illness; spread to CNS, skin, adrenals; higher incidence in kids and immunocompromised adults)

Question 5

Describe histoplasma histology at 37 deg C vs. 25 deg C.

Answer 5

• At 37 deg C: intracellular budding yeasts form in a multinucleate giant cell
• At 25 deg C: hyphae are septate and hyaline with macro and microconidia

Question 6

also known as “Chicago disease”

Answer 6

Blastomyces dermatitidis

Question 7

What are the clinical manifestations of Blastomyces dermatitidis?

Answer 7

• Cutaneous=classic! (necrotic and fibrotic skin lesions that may be mistaken for squamous cell carcinoma)
• Pulmonary (may be asymptomatic; may involve chest pain, productive cough, hilar lymphadenopathy, fever)
• Lytic bone lesions
• Disseminated disease

Question 8

How is Blastomyces dermatitidis infection acquired?

Answer 8

via inhalation

Question 9

What is the classic lab diagnostic feature of blastomycosis?

Answer 9

broad based budding yeast! (on KOH prep)

Question 10

With blastomyces, conidiophores arise at ____ angles to hyphae.

Answer 10

right

Question 11

Also known as “Valley Fever” and thought to be geographically restricted to desert climate.

Answer 11

Coccidioides

Question 12

True or false: Coccidioides is transmitted person-to-person.

Answer 12

False!

Question 13

Describe the clinical manifestations of primary coccidioidomycosis.

Answer 13

• Fever, cough, chest pain, malaise
• CXR: infiltrate, hilar lymphadenopathy, pleural effusion
• Most cases resolve spontaneously (w/ complete recovery)
• May get dissemination to bone, skin, squamous and mucosal tissues, meninges, joints, other sites (dissem. occurs more frequently in certain populations)

Question 14

What are the cutaneous manifestations of coccidioidomycosis?

Answer 14

• Erythema nodosum: multiple erythematous, painful nodules limited to extremities
• Erythema multiforme: target-like lesions occurring within first 48 hrs of initial symptoms; reflect a hypersensitivity response to infection

Question 15

What is the classic lab diagnostic feature of coccidioidomycosis?

Answer 15

spherules filled with endosproes

Question 16

How does infection with coccidioides occur?

Answer 16

inhalation of arthroconidia bypasses upper airway into alveoli –> monocytes ingest arthroconidia –> arthroconidia convert to spherules (NOT yeast!)

Question 17

What is a key feature of coccidioides seen on culture?

Answer 17

alternating arthroconidia (alternate with empty disjunctor cells)

Question 18

contains arthroconidia that typically alternate with empty disjunctor cells

Answer 18

coccidioides