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Question 8#

A 46-year-old man with a lifelong history of asthma develops worsening shortness of breath and a productive cough over the past 2 weeks. Laboratory samples are drawn in the Emergency Department and are shown below.

• Hemoglobin   13.2 g/dL
• Mean corpuscular volume   89 fL
• Mean corpuscular hemoglobin   31.0 pg
• Mean corpuscular hemoglobin concentration   34.5 g/dL
• Red cell distribution width   14.6 fL
• Leukocyte count   6,700/mm³
• Neutrophils   51%
• Lymphocytes   24%
• Eosinophils   22%
• Basophils   3%
• Platelets   250,000/mm³

A chest x-ray shows parenchymal infiltrates and evidence of bronchiolar dilation.

What is the most likely cause of his pneumonia?

A. Mycoplasma pneumoniae
B. Streptococcus pneumoniae
C. Klebsiella pneumoniae
D. Aspergillus
E. Acute HIV infection

Correct Answer is D

Comment:

Aspergillus. Allergic bronchopulmonary aspergillosis is a hypersensitivity reaction found most frequently among individuals with asthma or cystic fibrosis. Eosinophilic pneumonia is one manifestation of aspergillosis in such individuals. Aspergillus may be cultured from the sputum of such patients and septated hyphae may be seen under microscopic examination. Chest radiography will show infiltrates, atelectasis, and signs of bronchiectasis.

(A, B) Mycoplasma and S. pneumoniae are common causes of pneumonia, but would not produce eosinophilia. (C) Klebsiella pneumoniae is a common cause of pneumonia among individuals who have aspirated. (E) While acute onset of HIV may present with respiratory tract symptoms, it is not commonly associated with peripheral eosinophilia and radiographic findings suggestive of pneumonia.