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Which of the following findings is most likely to be observed in the lung lesions?
Dr. Shoaib Ahmad Baig
December 12, 2024
🔍 Question
A 21-year-old man with no prior health issues presents with fever, fatigue, muscle pain, and a dry cough that started two weeks after returning from a caving trip in Missouri. He does not smoke, drink alcohol, or use drugs. His temperature is 38.3°C (100.9°F), blood pressure is 120/70 mm Hg, pulse is 96/min, and respiratory rate is 16/min. Physical examination reveals crackles in the lungs. A chest X-ray shows patchy infiltrates in the lung tissue along with enlarged mediastinal and hilar lymph nodes.
Which of the following findings is most likely to be observed in the lung lesions?
A. Budding yeasts with a thick capsule
B. Macrophages containing small intracellular yeasts
C. Round spherules filled with endospores
D. Septate hyphae with dichotomous branching
E. Yeasts with pseudohyphae and blastoconidia
Correct Answer: Macrophages with Intracellular Small Yeasts
⚙️
🧠 Cave exposure in endemic region (Missouri)
⬇️
⚙️ Inhalation of Histoplasma capsulatum microconidia (fungal spores)
⬇️
🧠 Alveolar deposition
⬇️
⚙️ Phagocytosis by alveolar macrophages
⬇️
⚙️ Survival inside macrophages (inhibition of phagolysosome fusion 🛡️)
(Fungal defense mechanism)
⬇️
🧠 Intracellular replication of yeast form
⬇️
⚙️ Spread to hilar/mediastinal lymph nodes via lymphatics
⬇️
Granulomatous inflammation formation
⬇️
🔍 Findings in pulmonary lesions:
Macrophages with intracellular small yeasts (Histoplasma capsulatum)
🧠 Symptoms:
Fever, malaise, myalgia:
⚙️ Cytokine release (IL-1, TNF-α) ↑ systemic inflammation.
( Cytokines is an "alarm system 🚨" alerting the immune response.)
Nonproductive cough:
⚙️ Lung inflammation from macrophage recruitment & granuloma formation.
Lung crackles:
⚙️ Patchy infiltrates → alveolar exudates & granulomas (think of alveoli as “waterlogged filters 🛁”).
Mediastinal/hilar lymphadenopathy:
⚙️ Lymphatic spread & immune response in regional nodes.
Histoplasma in macrophages is like a Trojan horse 🏰
Macrophages unknowingly “carry” the pathogen inside them.
⬇️
⚖️ Contrasting Differentials
Option | Why Incorrect |
|---|---|
🛑 Budding yeasts with a thick capsule | Suggests Cryptococcus neoformans. 🧠 Seen in meningitis, typically in immunocompromised patients (not endemic to Missouri). |
🛑 Round spherules with endospores | Suggests Coccidioides. 🧠 Found in desert regions (e.g., Southwest US), not in Missouri caves. |
🛑 Septate hyphae with branching | Suggests Aspergillus. 🧠 Causes invasive infections in immunocompromised individuals, not granulomas. |
🛑 Yeasts with pseudohyphae | Suggests Candida. 🧠 Opportunistic infection (mucosal or bloodstream), not primary pulmonary disease. |
⬇️
📝 Flashcards
Stay Hungry, Stay Curious!
Your Brother In This Struggle
Dr. Shoaib Ahmad
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