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Questions and Answers
If a patient is diagnosed with a severe case of blastomycosis, which treatment option would be the MOST appropriate initial course of action?
If a patient is diagnosed with a severe case of blastomycosis, which treatment option would be the MOST appropriate initial course of action?
- Initiation of amphotericin B therapy. (correct)
- Observation without intervention, as blastomycosis is typically self-limiting.
- Surgical excision of granulomas followed by itraconazole treatment.
- Prescription of oral fluconazole to penetrate the spinal fluid.
A patient presents with a lung infection caused by a systemic mycosis that exhibits intracellular parasitism. Which of the following organisms is MOST likely responsible?
A patient presents with a lung infection caused by a systemic mycosis that exhibits intracellular parasitism. Which of the following organisms is MOST likely responsible?
- Coccidioides immitis.
- Histoplasma capsulatum. (correct)
- Blastomyces dermatitidis.
- Paracoccidioides brasiliensis.
Which diagnostic method provides the MOST definitive identification of Histoplasma capsulatum?
Which diagnostic method provides the MOST definitive identification of Histoplasma capsulatum?
- Microscopic examination of tissue biopsy specimens.
- Isolation and culture of the organism or detection of exoantigens in urine. (correct)
- Radiological imaging of lung infiltrates.
- Detection of antibodies in serum samples.
A patient with a history of exploring bat-infested caves develops histoplasmosis. What aspect of Histoplasma capsulatum’s life cycle and transmission is MOST relevant to this scenario?
A patient with a history of exploring bat-infested caves develops histoplasmosis. What aspect of Histoplasma capsulatum’s life cycle and transmission is MOST relevant to this scenario?
A patient is diagnosed with blastomycosis after presenting with skin lesions and lung infiltrates. Microscopic examination of a tissue biopsy is performed. Which microscopic characteristics would MOST strongly support this diagnosis?
A patient is diagnosed with blastomycosis after presenting with skin lesions and lung infiltrates. Microscopic examination of a tissue biopsy is performed. Which microscopic characteristics would MOST strongly support this diagnosis?
What is the MOST critical factor determining whether a person develops a disseminated form of histoplasmosis rather than a localized pulmonary infection?
What is the MOST critical factor determining whether a person develops a disseminated form of histoplasmosis rather than a localized pulmonary infection?
Which of the following statements BEST explains why fluconazole is sometimes preferred over other antifungal medications in treating disseminated histoplasmosis?
Which of the following statements BEST explains why fluconazole is sometimes preferred over other antifungal medications in treating disseminated histoplasmosis?
A researcher is developing a new diagnostic assay for blastomycosis. Which of the following fungal structures would be the MOST appropriate target for a highly specific assay?
A researcher is developing a new diagnostic assay for blastomycosis. Which of the following fungal structures would be the MOST appropriate target for a highly specific assay?
In the United States, which of the following systemic mycoses MOST commonly affect immunocompetent individuals?
In the United States, which of the following systemic mycoses MOST commonly affect immunocompetent individuals?
A patient is suspected of having a systemic mycosis. What is the MOST common route of transmission for these types of infections?
A patient is suspected of having a systemic mycosis. What is the MOST common route of transmission for these types of infections?
Flashcards
Systemic Mycoses
Systemic Mycoses
Fungal infections affecting the entire body or multiple organ systems. Divided into those infecting healthy individuals (true pathogens) and those infecting immunocompromised individuals.
Blastomycosis
Blastomycosis
Caused by Blastomyces dermatitidis, acquired by inhaling microconidia. Primarily affects the lungs but can disseminate to skin, bone, and genitourinary tract.
Blastomycosis Treatment
Blastomycosis Treatment
Itraconazole is the first choice, Amphotericin B for severe cases, and surgical excision may help.
Histoplasmosis
Histoplasmosis
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Histoplasmosis Pathogenesis
Histoplasmosis Pathogenesis
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Histoplasmosis Treatment
Histoplasmosis Treatment
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True pathogens (mycoses)
True pathogens (mycoses)
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Coccidioidomycosis
Coccidioidomycosis
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Paracoccidioidomycosis
Paracoccidioidomycosis
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Coccidioidomycosis Treatment
Coccidioidomycosis Treatment
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Study Notes
- Systemic mycoses are fungal infections affecting the entire body
- They are classified into true pathogens that infect healthy people and those that infect immunocompromised individuals
- Common in the US are coccidioidomycosis, histoplasmosis, and blastomycosis
Blastomycosis
- Blastomyces dermatitidis causes blastomycosis, also known as North American blastomycosis
- Microconidia from the soil become airborne and enter the lungs
- In the lungs, microconidia germinate into thick-walled yeast cells with unipolar, broad-based buds
- Primary infection site is the lungs
- Secondary sites after dissemination include skin, bone, and the genitourinary tract that manifest as isolated granulomas
- Diagnosis involves microscopic examination of tissue biopsy
- Thick-walled yeast cells with broad-based buds are seen microscopically
- A B-cell assay is available to detect nucleic acids of Blastomyces
- Itraconazole is the preferred treatment
- Amphotericin B is for severe cases
Histoplasmosis
- Histoplasma capsulatum causes histoplasmosis and is a dimorphic fungus
- Forms tuberculated macroconidia (for lab ID) and microconidia (transmit infection)
- Histoplasma grows in soil contaminated with bird or bat droppings
- Inhalation of spores leads to conversion into yeast-like cells inside macrophages
- Can be acute, benign, and self-limiting
- In older or T-cell deficient individuals it can spread
- Dissemination affects the reticuloendothelial system
- Histoplasma capsulatum exhibits intracellular parasitism
- Diagnosis involves microscopic examination of tissue samples/bone marrow
- Yeast cells inside macrophages are seen microscopically
- Definitive diagnosis achieved through organism isolation/culture or exoantigen detection in urine
- Mild infections require no therapy
- Itraconazole is effective for progressive cases
- Amphotericin B is the preferred treatment for disseminated disease
- Fluconazole is often used for spinal fluid penetration
Coccidioidomycosis
- Coccidioides immitis causes coccidioidomycosis
- Endemic in arid regions of the southwestern US and Latin America
- Exists as a mold in soil and a spherule in tissues
- Hyphae are formed in the soil, with alternating arthrospores
- Arthrospores are carried by the wind
- Arthrospores are inhaled and can infect the lungs
- In the lungs, arthrospores form spherules with endospores
- When the wall ruptures, endospores are released and differentiate to form new spherules
- Granulomatous lesions can occur in bones and the central nervous system and cause meningitis
- Infection of the lungs is often asymptomatic
- Symptoms include influenza-like illness with fever and cough
- About 50% of cases show changes in the lungs
- Tissue specimens show spherules
- No treatment is needed for mild infections
- Amphotericin B or itraconazole is used for persistent infections
- Fluconazole is the drug of choice for meningitis
Paracoccidioidomycosis
- Paracoccidioidomycosis is caused by Paracoccidioides brasiliensis
- It is also called South American blastomycosis
- Spores are inhaled, leading to lung lesions
- It is similar to histoplasmosis and blastomycosis
- The most common secondary site of infection is the mucosa of the mouth and nose
- Painful, destructive lesions may develop
- 90% of symptomatic cases occur in mature males
- In tissue specimens, yeast cells with multiple buds resembling a "ship's wheel" are seen microscopically
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