Repeated USMLE Questions Step 1- 165

Two sisters, aged 40 and 45 years old, are brought to the emergency room presenting with severely dramatic pneumonia. When the lungs are examined, doctors are able to easily hear rales. The chest x-rays reveal that both sisters have bilateral and diffuse infiltrates. On taking down their history, it was observed that 2 weeks ago both sisters went hiking to a mountainous area where they explored a dusty cave.

What would be the most likely causative agent of their condition?

A- Hemophilic influenzae

B- Blastomyces dermatitidis

C- Coxsackie A virus

D- Histoplasma capsulatum


The sisters are suffering from acute pulmonary histoplasmosis, which is a respiratory infection caused by inhalation of the spores of the Histoplasma capsulatum fungus. It is commonly found in bird and bat droppings, something which you would likely find in caves. You get sick upon breathing in the spores produced by the fungus.

The correct answer is D

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