Systemic Mycoses Flashcards
1
Q
the big 4 mycoses in the US?
A
- coccidioides
- histoplasma
- blastomyces
- paracoccidioides
2
Q
major themes
A
- environmental- spores/ fungi in soil
- inhaled into lungs
- thermal dimorphism
- wide range of severity: asymptomatic clearance to death
- NOT person to person
- coccidio, histoplasma, blastomyces may mimic TB, source is American dirt, not foreign crowds
- drug resistance is low
3
Q
coccidio
A
- coccidiodes immitis (most common)
- C. posadasii
- dimorphic- mold in soil, spherule in tissue
- grow in the rainy season as mycelia (noninfectious)
- in dry summer, forms hyphae with alternating athrospores and empty cells
- when disturbed by wind or excavation, readily release arthroconidia (infectious)
- spores are carried by the wind and inhaled by humans
- can have asymptomatic seroconversion in a healthy person
4
Q
coccidio 2
A
- endemic in southwest US and Latin America, may travel home in returning patient or arrive in contaminated shipped material
- caseload has increased as endemic areas have become population areas (old people go southwest!!)
- symptomatic disease can keep a previously healthy person out of school or work for a month
- was considered rare and uniformly fatal until 1929 when some med student named Harold Chope inhaled it and got lung illness accompanied by erythema nodosum
5
Q
pathogenesis of coccidio
A
- athrospores (arthroconidia) are inhaled
- infectious dose can be as low as a single IU, though high dosage more likely to cause symptoms
- within terminal bronchiole they change form
- spherules are highly resistant to eradication by immune system
- 30 micrometer in diameter
- thick, double refractive wall
- filled with endospores
- wall ruptures to release endospores develop into new spherules
- spherules and endospores aren’t infectious
- *endospores can make new spherules in lung but not new arthrospores
6
Q
what can happen with low dose and healthy innate immunity?
coccidio
A
-asymptomatic clearing
7
Q
what happens with a moderate dose and healthy CMI?
Coccidio
A
- asymptomatic containment
- nonspecific flulike illness, containment
- mild, pneumonia, erythema, nodosum, containment
8
Q
what happens with a high dose and immunosuppressed?
Coccidio
A
- serious pneumonia
- dangerous dissemniation
9
Q
acute phase of coccidio pathogenesis?
A
-innate immunity (macrophage response) attempts to clear infection and is often successful
10
Q
chronic phase of coccidio pathogensis?
A
- innate immunity inadequate for clearance
- lymphocytes and histiocytes initiate granuloma and giant cell formation (containment)
- if CMI is healthy, infection is contained in granulomas in the lung, many eventually cleared asymptomatically
- many patients who become ill have nonspecific flulike symptoms that resolve at home
- 60% exposures= asymptomatic +flulike
11
Q
symptomatic disease of coccidio?
A
- symptomatic disease may appear as valley fever or desert rheumatism
- fever
- arthralgias
- erythema nodosum- immunogenic, painful tender rash esp on shins
- erythema multiforme
- chest pain
12
Q
coccidio pathogenesis 2?
A
- if immunosuppressed, disseminated infection both by intracellular travel in macrophages and hematogenous spread
- risk factors- advanced age, immunocompromise, late stage pregnancy, occupational high level exposure (farmers, construction), black or Fillipino race
- may affect any organ, primarily seen in bones and meninges
- induces immune anergy, may be rapidly fatal
- localized extrapulmonary infection may also result from contaminated injury, usually resolves without treatment
13
Q
coccidio Dx on exam
A
- usually summer or autumn, incubates 7-30 days
- obtain history of travel to or residence in endemic area
- PPD with coccidio or pherulin
- if exposed with cleared or contained infection
- neg is unexposed or disseminated infection
14
Q
what does contained infection look like on exam?
Coccidio
A
\+PPD -often asymptomatic -may have flu like illness 50% have lung changes on xray -infiltrates -adenopathy -effusions -nodules resembling malignancy -bronchoscopy may be useful -10% develop erythema nodosum in adults, erythema multiform in peds or arthralgias
15
Q
erythema nodosum
A
- desert bumps, hypersensitivity reaction
- red, tender nodules on exterior surfaces like lower legs
- delayed cell mediated hypersensitivity to final antogens
- immunogenic complication of granulomatous diseases
- hypersensitivity may also manifest in eye as conjunctivitis
- EN means risk of dissemination is low
16
Q
what does disseminated infection look like on exam?
Coccidio
A
- may affect any organ most common:
- meninges, classic sx but insidious onset
- bone (osteomyelitis)
- skin or lymph node (soft tissue abscess, hematogenously seeded)
- disseminates in 1% of general population, 10% of African American, Fillipino, late pregnancy patients, diabetes, pre-existing cardiopulmonary
- dramatic sweats, dyspnea, fever, weight loss
- erythema nodosum is a good sign
- may arise after prolonged incubation or reactivated after treatment
- night sweats, dyspnea, fever, weight loss, and chronic cough may also appear in smokers from chronic lung infection
17
Q
coccidio dx on lab
A
- take biopsies of relevant tissues, CSF, blood, urine, stain with H&E or fungal stains, look for spherules
- cultures on sabourauds agar at 25C: cottony white mold composed of hyphae with arthrospores (cultures are infectious!) biosafety level 3
- serology for exposure, titers (IgG from blood and/or CSF), titer spikes if disseminating
- positives are very reliable, but some false negatives occur
- PCR available
18
Q
CSF of coccidio?
A
-lymphocytic pleocytosis, elevated protein, hypoglycorrgachia, eosinophilia, CF IgG
