Systemic Mycoses Flashcards
List the fungi that are considered systemic mycoses (4)
Histoplasma capsulatum
Blastomycosis dermatitidis
Coccidioides immitis
Paracoccidioides brasiliensis
For fungal infections in general, who is most at risk for developing systemic disease?
The immunocompromised. Many fungal infections are asymptomatic in most healthy people.
What disease is caused by histoplasma?
Histoplasmosis
Geographic area endemic to histoplasmosis
Midwestern/central USA along Mississippi and Ohio River Valley
Histoplasmosis transmission
Through respiratory tract. Associated with bird or bat droppings. Spores in bird/bat droppings are inhaled - these go to the lungs. Then they get ingested by macrophages.
May mention someone who has recently been in a cave or has been exposed to chicken coups (farmer)
What would histoplasmosis look like under microscope?
Macrophage filled with small, intracellular oval bodies. It is ovoid.
Sample is stained with KOH Prep.
Histo is much smaller than a RBC. Macrophage is only slightly larger than a RBC, Many Histo’s can fit inside the macrophage.
How do you diagnosis histoplasmosis?
Culture - takes a long time
Better option is rapid histoplasma urine or serum antigen tests
Histo dimorphism
Mold in the cold (soil). Yeast in the heat (body).
Histoplasmosis clinical presentation
Normally, the systemic fungi do not produce any symptoms, but they can cause granulomas
In the unlucky few that do show symptoms, it causes a pneumonia.
Lungs develop granulomas which eventually calcify leading to chronic pulmonary issues
Chronic Histo looks a lot like TB - cavitary lesions in upper lobes, calcified nodules with fibrotic scarring (mostly in hilar region)
Besides pneumonia, Histo can also cause erythema nodosum - painful red nodules on shins (normally)
Systemic Histoplasmosis Presentation
Systemic fungi are especially associated with the immunocompromised
When an immunocompromised person gets histo they get hepatosplenomegaly
Gross path will show calcifications in liver and spleen - the fungus targets reticuloendothelial system which has lots of macrophages.
Patients can also develop skin and neuro findings
Histoplasmosis Tx
Local/mild infection: Use azole drugs (Fluconazole, Ketoconazole)
Systemic: Amphoteric B - lots of side effects, reserved for life-threatening systemic cases
What geographic region is most associated with Blastomycosis?
Great Lakes and Ohio River Valley (some southern too) - similar to Histo. Blasto is on east coast though… Histo doesn’t reach that far east
Blastomycosis dimorphism
Mold in the cold (soil), Yeast in the heat (body)
Blastomycosis transmission
Inhalation of aerosolized spores
Blastomycosis replication
Single broad-based budding once it’s in the body
What does Blasto look like?
Fairly large. Same size as RBC.
Blasto in the lungs
Causes lungs to have patchy alveolar infiltrate on CXR (haziness). Also lesions and cavitations.
Pneumonia can be acute or chronic and is considered a local lung infection.
Majority of infections are subclinical.
Blastomycosis dissemination
Immunocompromised
Dissemination from lungs most likely occurs in skin and bone
Osteomyelitis
Diagnosis of Blastomycosis infection
Done through KOH prep or through culture
On KOH you’ll see round yeast with single, broad based bud.
Can also detect with rapid urine antigen test
Blastomycosis Tx
Local: Azoles (Itraconazole)
Disseminated: Amphotericin B (usually in immunocompromised)
What geographic region is most associated with coccidioides?
California and SW USA
Coccidioides transmission
Inhalation of spores in dust
Chance of infection goes up a ton when large amounts of dust goes into the air - frequent dust storms in San Joaquin Valley of California cause large incidence
Coccidioides infection sometimes called “San Joaquin Valley Fever”
Large amounts of dust is also kicked up during earthquakes - incidence can increased 10x
Coccidioides dimorphism
Mold in Cold
Spherules filled with endospores in the body (WHAT?! IT’S DIFFERENT?!?!)
What does coccidioides look like?
Spherules are larger than RBCs
Coccidio > Blasto > Histo
Coccidioides presentation
Asymptomatic/subclinical in most healthy people
In some, it presents as self-limited acute pneumonia with fever, sweats, arthralgias - can last for a couple weeks
Radiographic images may show either nothing (majority of cases) or cavities and/or nodules
Also associated with erythema nodosum (red, extremely tender nodules on shins)
REMEMBER! E.N. represents a robust immune response (you don’t see this in immunocompromised)
Disseminated Coccidioides
Immunocompromised
May disseminate to the bone in these patients (skin and lungs too)
Can also disseminate to meninges and cause meningitis
Coccidioides diagnosis
KOH stain or culture (takes a while). Could send off serum and check for antibodies too (like all systemic mycoses - IgM presence against it demonstrates infection)
Coccidioides Tx
Local: Ketoconazole
Systemic: Amphotericin B
What geographic region is most often associated with paracoccidioides?
Brazil and South America
What does paracoccidioides look like?
“Captain’s Wheel” in yeast form (in the lungs)
Very large. ~ Coccidioides size.
Paracoccidioides = Coccidioides > Blasto > Histo
Paracoccidioides dimorphism
Mold in environment
Yeast in heat
Paracoccidioides transmission and presentation
Respiratory droplets
Once these are inhaled, the fungus disseminates and causes lymphadenopathy - cervical, axillary, even inguinal
As it progresses from cervical it moves down to affect upper respiratory tract and lungs - causing granulomas in lungs
Development of mucosal ulcers in Upper Respiratory Tract - mucocutaneous lesions (esp mouth) - often in gums
Have ragged borders with small spots of hemorrhage
Remember!! Mucocutaneous lesions and lymphadenopathy
Paracoccidioides Tx
Local: Itraconazole
Severe: Amphotericin B
