Question
A 30-year-old woman presents with persistent dry cough, fatigue, and low-grade fever. Physical examination shows marked pallor, respiratory distress, nasal flaring, and intercostal retractions. A chest X-ray reveals diffuse, bilateral interstitial infiltrates. A photomicrograph of bronchoalveolar lavage is shown. Which of the following etiologic agents is most likely responsible for this patient’s pulmonary disease?
| A. |
Aspergillus fumigatus
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| B. |
Legionella pneumoniae
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| C. |
Mycoplasma pneumoniae
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| D. |
Pneumocystis jiroveci
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Show Answer
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Correct Answer � D
Explanation
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Answer : D Pneumocystis jiroveci
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P. jiroveci (formerly P. carinii) was identified in malnourished infants at the end of World War II.
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It causes progressive, often fatal pneumonia in persons with impaired cell-mediated immunity and is one of the most common opportunistic pathogens in persons with AIDS.
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The organism is now classified with the fungi. The infection begins with the attachment of trophozoites to the alveolar lining.
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Trophozoites feed, enlarge, and transform into cysts within the host cells. Eventually, the cysts burst, releasing new trophozoites. Progressive consolidation of the lung ensues. Although the other choices cause pneumonia, they do not exhibit these characteristic cysts.
