Fungi

Question 1

Tineas

Answer 1

• = Cutaneous fungi
• Almost all are transmitted human-to-human or zoonotic
• Three key genera:
  
  • Microsporum does not infect nails
  • Epidermophytan does not infect hair
    
    • Does not make microconidia → cannot be eaten by macrophages
  • Trichophytan infects nails, hair, & skin
• Terbinafine often used to treat b/c it accumulates in skin and nails.

Question 2

Microsporum

Answer 2

• Scaly patch on scalp
• Fluoresces w/ UV Wood’s Lamp

Question 3

Sporothrix schenckii

Answer 3

• = subcutaneous fungus
• CP: rose thorn puncture → nodule that is not particularly painful
• Weird garden disease that is best not to ignore: initial infection site appears as a small nodule which may ulcerate. About 2 weeks later, secondary nodules appear and a chain of nodules along lymph appear; these can ulcerate

Question 4

Systemic mycoses

Answer 4

• Coccidiodes imminitis
• Histoplasma capsultam
• Blastomyces dermatitidis
• Paracoccidiodes brasiliensis
• All dimorphic fungi
• All airborne transmission

Question 5

Coccidiodes immitis

Answer 5

• Travel to Arizone/SW US
• Cough, fever, recent hemoptysis (lung infections of varying severity)
• “Valley Fever”
• Coccidiodes is not a yeast in the beast; it forms spherules
  
  • “spherule filled with endospores”
• From the lungs, Coccidoides most commonly disseminates to bone marrow and CNS

Question 6

Histoplasma capsulatum

Answer 6

• “Dry, hacking, cough”
• Spelunking or cave-exploring
  
  • ​Bat and chicken poop
• Ohio & Mississipppi River Valleys
• Also Mexico & Central & South America
• Intracellular pathogen
  
  • Lives to live in macrophages
  • “Macrophage filled with round cells”
• Becomes disseminated in immunocompromised and goes to bone

Question 7

Blastomyces dermatiditis

Answer 7

• Broad based budding yeast
• Wider range around Ohio and Mississippi River Valley
• Can inhale it OR get it from the skin
• Frequently fatal, even in immunocompetent people, because they often think it is the flu or the cold and they stay home with it.
• Rarely disseminates, but when it does, it goes to bone, skin, & GU

Question 8

Paracoccidiodes brasiliensis

Answer 8

• CP:
  
  • Persistent cough w/ purulent sputum
  • CXR w/ nodular infiltrative lesions
  • Travel in South America
• “Pilot/Captain’s wheel” appearance of multiple budding yeast

Question 9

Opportunistic mycoses

Answer 9

• Candida albicans
• Cyptococcus neoformans
• Aspergillis fumigatus
• Pneumocystis jiroveci
• Mucor and Rhizomucor spp.

Question 10

Mucor and Rhizomucor spp

Answer 10

• Zygomycetes - form big hollow straws/tubes of aseptate hyphae
• CP:
  
  • Poorly controlled diabetic → these fungi really like glucose
  • pigmented lesion on FACE
• People breathe them in, but they don’t go farther than sinuses
• Tx with Amphotercin B

Question 11

Aspergillis fumigatus

Answer 11

• CP: neutropenic, septate hyphae w/ acute-angle branching
• Can get a big fungal ball in the lung (e.g., after TB)

Question 12

Cryptococcus neoformans

Answer 12

• CP: HIV+, fever, headache, seizure, drowsy
• Grows in pigeon poop
• Think:
  
  • HIV-associated meningitis
  • Budding yeast w/ a serious capsule
    
    • ​on india ink stain
    • Outer circle is all polysaccharide. Inner line circle is the cell wall.
      
      • Makes this to:
        
        • Evade our immune system
        • Prevent its desiccation (so it can survive longer)

Question 13

Microsporidia

Answer 13

• CP: s/p renal transplant, intermittent watery diarrhea
• Weird fungi
• Sometimes incorrectly classified as protozoa.
• They are a diagnosis of exclusion for GI and CNS infections.