Endemic Mycoses Flashcards
difference between dimorphic fungi and other fungi.
Dimorphic fungi exist as mold in environment and transform to yeast in human host
Describe how endemic mycoses are acquired.
- all acquired by inhalation of spores
- specific geographic locations
- acute and/or reactivation disease (reactivation may occur outside of area of endemicity)
- ranges of disease severity: can cause serious disease in normal hosts
- H. capsulatum, C. immitis, and P.marneffei are major opportunistic pathogens
Histoplasmosis mode of transmission
- Mold lives well in soil with high nitrogen content - areas contaminated with bird or bat droppings
- Disturbance of soil results in aerosolization of microconidia.
- Outbreaks associated with soil disturbance.
- exposure to caves and bird roosts
- excavation and demolition of old buildings
- Ohio and Mississippi river valleys of the U.S.,
Histoplasmosis pathogenesis
Spores -> Lungs -> yeast form -> into macrophages -> RES
-Multiply within macrophages
-Travel to hilar and mediastinal LNs
-Spread thru entire reticuloendothelial system (lungs, lymph nodes, liver, spleen, bone marrow)
2-3 weeks after infection develop cellular immunity.
-Macrophages become fungicidal
-Develop necrosis with fibrous encapsulation (granuloma)
-Calcium deposition and, within a few years, calcified granulomas
-small #s of yeast remain viable within granulomas and can cause relapses of disease
Histoplasmosis Clinical Manifestations
-most infected individuals are asymptomatic
Pulmonary syndromes
-Acute
-usually mild, self-limited illness (Sxs 10-14d after exposure)
-more severe after heavy inoculum
-fever, sweats, cough, occ HA and GI complaints
-diffuse pulmonary infiltrates, +/- hilar or mediastinal LNs
Subacute – presents over weeks
-fever, sweats, cough, weight loss
-hilar or mediastinal lymphadenopathy
-possible focal or patchy pulmonary infiltrates
Chronic – inability to clear the infection
- F, cough, sweats, weight loss
-interstitial or consolidative infiltrates
+/- bullae, +/- calcifications
Mediastinitis
-frequent complication of pulmonary histoplasmosis
-can lead to acute pericarditis and cardiac tampanode
Progressive disseminated histoplasmosis
-patients with compromised cell-mediated immunity and patients on TNFα inhibitors
-fever, wt loss, sweats
-hepatosplenomegaly and lymphadenopathy (but less than 50%)
-hematologic abnormalities due to bone marrow involvement
respiratory distress
-possible GI, adrenal, CNS, and mucosal involvement
-Consider histoplasmosis whenever TB is being considered.
Histoplasmosis Diagnostic Tools
- Culture:
- good:“gold standard”
- bad: 2-4 weeks to get results; low sensitivity
- Fungal stain
- Good: rapid
- Bad: low sensitivity
- Serology:
- Good: rapid, high sensitivity
- Bad: false – (immunocompromised &1st few weeks after exposure); false + (cross-reacts other fungi)
- can’t differentiate active vs prior infxn
- Antigen:
- Good: rapid
- Bad: low sensitivity in localized dz
Histoplasmosis Treatment
- Primary self-limited: none
- Moderate disease: Itraconazole
- Severe disease: Amphotericin B
- HIV pts may require lifelong suppressive Rx
Blastomycosis Mode of transmission
- Mold grows in soil and leaf litter.
- Disturbance of soil results in release of spores.
- Dogs are 10x more susceptible than humans.
- history of a pet dog recently ill may be a clue to the diagnosis
Blastomycosis Pathogenesis
- Inhalation of conidia into alveoli.
- Organisms change to the yeast form in the lungs.
- Multiply by budding.
- Hematogenous dissemination may occur before immunity develops.
Blastomycosis Clinical Presentation
-Most cases probably asymptomatic/subclinical
-Most common clinical manifestations
1. pulmonary
2. cutaneous
3. bone
4. genitourinary
Pulmonary disease
-Acute pneumonia
-frequently presents as atypical pneumonia with alveolar
-infiltrates that doesn’t respond to usual antibioticss
-mass-like lesions frequently misdiagnosed as cancer
Subacute and chronic pneumonia
–fever, sweats, fatigue, weight loss
Radiology: varied
-alveolar infiltrate, mass-like lesion, multiple nodules
-lobar infiltrates, and cavitary lesions can be seen
Non-pulmonary manifestations of blastomycosis
-COMMON
1.cutaneous lesions: verrucous w/ raised border or ulcerative
2.GU tract infection – prostatitis and epididymoorchitis
3.osteomyelitis (up to ¼ of extra-pulmonary cases)
-LESS COMMON
-septic arthritis
-laryngeal and orpharyngeal nodules
-ocular infection
-meningitis
-intracerebral abscesses
Blastomycosis Diagnostic Tools
- Histopathology
- Culture: colonization not believed to occur, so any culture + for Blastomycosis is considered pathogenic.
- Serology not particularly helpful for clinical diagnosis (poor specificity)
Blastomycosis Treatment
Mild disease: itraconazole
Severe disease: amphotericin B
Coccidioidomycosis Mode of Transmission and Pathogenesis
Mode of Transmission
-people acquire infection by breathing in arthrocondia
Pathogenesis
- Fungus grows in sandy soils of southwest
- Grows wing like chains caused Mycelia that allow it to become airborne
- Living spores take flight w/ wind and other disturbances
- Once airborne, spores are easily inhaled
- In the lungs the spores become spherules that begin replicating and filling the lung
Coccidioidomycosis Clinical Presentationi
-A spectrum of disease: 50-70% of patients with asymptomatic infection
-Most common presentation: Self-limited pneumonia 1-3 wks after exposure
-Symptoms: fever, cough, chest pain, fatigue, shortness of breath, chills,
-muscle and joint aches, night sweats, weight loss
-these can last for several months.
-5-10% have persistent pulmonary symptoms
-develop residual pulmonary sequelae such as nodules or peripheral thin-walled cavities.
Eosinophilia in about 25% of patients
Extrapulmonary coccidioidomycosis
Dissemination to skin, bone, and meninges most common
Very uncommon in immunocompetent hosts
- 0.5% of infxns within persons of Caucasian ancestry
Coccidioidomycosis Diagnostic Tools
- Direct microscopic evaluation of sputum or tissue
- Culture at 25°C (tell lab b/c v infectious)
- Serology (rising titers are bad prognostic sign)
