Fungal Infections

Question 1

list the endemic vs. opportunist fungi

Answer 1

• endemic:
  
  • histoplasmosis
  • coccidioides
• opportunistic:
  
  • candida
  • aspergillus
  • mucor
  • cryptococcus
  • pneumocystis jiroveci

Question 2

describe the damage by fungal infections and an exception

Answer 2

• causes tissue inflammation (mixture of acute and chronic)
• the presence of PMN + lymphocytes + monocytes + giant cells
• tendency to invade blood vessels → hemorrhage, thrombosis, infarction
• exceptions:
  
  • cryptococcus: elicits minimal or absent inflammatory cell infiltrate in immunodeficient hosts

Question 3

describe th etiology and risk factor pneumocystis jeroveci pneumonia (PCP)

Answer 3

• etiology:
  
  • P. jiroveci
• risk factor:
  
  • advanced HIV infection (<200 CD4 T-cell); may also affect severe malnourished children, organ transplant patients and individuals on chemotherapy

Question 4

describe the clinical features and diagnosis of PCP

Answer 4

• clinical features:
  
  • SOB, dry cough, hypoxia
• diagnosis:
  
  • CXR (best initial test)
  • bronchio-alveolar lavage

Question 5

describe the 4 types of candidiasis

Answer 5

caused by Candida albicans

1. oral thrush: gray-white, dirty gray pseudomembrane
2. esophagitis: seen in AIDS and hematolymphoid malignancies
   
   • presentation: odynophagia
3. vaginitis: seen in diabetes, pregnancy, oral contraceptive pills
   
   • itching, soreness, redness, thick (creamy cheese) discharge
4. skin infection: onychomycosis, paronychia, folliculitis, balanitis, diaper rash
5. invasive candidiasis
   
   • immunocompromised patient
   • causes candidemia with wide spread abscesses in the brain, eyes, kidney, bones, lung, liver, heart
   • candida endocarditis: most common fungal endocarditis
     
     • occurs in pt with prosthetic heart valves or IV drug abusers

Question 6

describe the investigations of Candidiasis

Answer 6

• investigation: PAS stain → pink slender hyphae

Question 7

describe what is seen in the image

Answer 7

Question 8

describe the etiology and risk factors for Cryptococcus infections

Answer 8

• etiology:
  
  • Cryptococcus neoformans: budding yeast with narrow-based buds; surrounded by a thick capsule
    
    • found in pigeon excretions
• risk factors:
  
  • HIV/AIDS, organ transplant, leukemia and lymphomas

Question 9

describe the pathogenesis of Cryptococcus infections

Answer 9

• pathogenesis:
  
  • the polysaccharide capsule is a major virulence factor, inhibiting phagocytosis, leukocyte migration and recruitment of inflammatory cells
  • primary lung disease (40%): granulomatous inflammation with caseation
    
    • do NOT have to be immunocompromised

Question 10

describe a complication of Cryptococcus infection

Answer 10

• if disseminated: meningitis and meningoencephalitis

Question 11

describe the cycle of Cryptococcus infection

Answer 11

Question 12

describe the clinical features of Cryptococcus infections

Answer 12

• clinical features:
  
  • lung: fever, dry cough, SOB and chest pain
  • brain: fever, headache, confusion, nausea and vomiting
    
    • brain gross examination: cystic spaces containing “soap bubble” like organisms

Question 13

describe investigations of Cryptococcus infections

Answer 13

• investigations:
  
  • sputum and BAL
  • PAS, silver stain, mucicarmine
  • CSF: add a drop of India ink → organisms appear as clear halo → negative staining (best initial test)
  • latex agglutination test: using antibodies that detects cryptococcal antigens in blood and CSF (most specific test)

Question 14

describe what is seen in the image

Answer 14

Question 15

describe what is seen in the image

Answer 15

Question 16

describe what is seen in the image

Answer 16

Question 17

describe the etiology of aspergillosis

Answer 17

• opportunistic fungal infection: occurs with weakened immunity or with the presence of an underlying lung disease
• caused by Aspergillus fumigatus
• ubiquitous in nature, spores can be isolated from air anywhere on earth

Question 18

describe allergic bronchopulmonary aspergillosis

Answer 18

• common in patients with asthma
• can lead to COPD in untreated
• IgE mediated (type I hypersensitivity reaction
• presents as worsening asthma (cough, wheezing, SOB)

Question 19

describe aspergilloma

Answer 19

• also called fungal balls
• occurs after the fungus colonizes pre-existing lung cavities (TB, old abscesses)
• can cause massive hemoptysis in 60-80% of patients

Question 20

describe invasive aspergillosis

Answer 20

• occurs in severely immune suppressed patients
• necrotizing pneumonia with vascular invasion
• presents with cough, dyspnea, pleuritic chest pain and sometimes, hemoptysis
• vascular involvement can lead to hemorrhagic infarctions
• can disseminate to heart, brain kidney

Question 21

describe investigations of aspergillosis

Answer 21

• investigation:
  
  • demonstrate hyphae by PAS, silver stains
    
    • hyphae have frequent septae, narrow angled (<45 degrees)

Question 22

describe what is seen in the image

Answer 22

Question 23

describe the etiology of mucromycosis

Answer 23

• caused by zygomycetes (Rhizopus and mucor)
• opportunistic infection:
  
  • common in immunosuppressed patients
  • associated with diabetes-1 (DKA)

Question 24

describe the pathogenesis of mucormycosis

Answer 24

• pathogenesis:
  
  • route of entry: spores inhalation, ingestion or via skin
  • colonize nasal cavity/sinuses → extend to brain, orbit and other head/neck structures
  • can affect the lungs (cavitation) or gut (among malnourished)
  • marked vascular invasion → necrosis, infarction

Question 25

describe the clinical features of mucormycosis

Answer 25

* clinical features: * **rhinocerebral** **mucormycosis**: headache, nasal congestion, black pus discharge and fever * late symptoms: diplopia, visual loss, proptosis and confusion * **pulmonary mucormycosis**: cough, hemoptysis, SOB * **GI mucromycosis:** abdominal pain, bloody stool and diarrhea

Question 26

describe the investigations for mucormycosis

Answer 26

* investigations: * MRI/CT scan, biopsy with silver stain, PAS * **non-septate hyphae, which branch at 90 degree angles**

Question 27

Answer 27

Question 28

describe the etiology of histoplasmosis

Answer 28

* caused by histoplasma capsulatum * most common systemic fungal infxn * endemic in Ohio and central Mississippi river valleys * exposure occurs in construction sites, caves * inhalation of spores in dust contaminated with excreta from bats, starlings or chickens

Question 29

describe the pathogenesis of histoplasmosis

Answer 29

* weakened immunity → inhalation of spores → multiplication within macrophages → spread to different organs via lymphatics

Question 30

describe the clinical features of histoplasmosis

Answer 30

* usually asymptomatic * if symptoms occur, they are nonspecific; flu-like syndrome usually self-limited * fever, fatigue, night sweats, dry cough +/- hemoptysis * similar to TB

Question 31

describe the pathology/morphology of histoplasmosis

Answer 31

* acute (primary) pulmonary infxn * chronic (granulomatous) pulmonary disease * disseminated military disease

Question 32

describe the investigations of histoplasmosis

Answer 32

* investigations: * CXR, CT scan * serology * BAL with Gomori Methenamine Silver (GMS) stain * fine needle aspiration cytology from LN or lungs

Question 33

Answer 33

Question 34

Answer 34