1 infec 93 - tabish60102

[ArchivalUser]

A 45-year-old woman is hospitalized in December because of a 1-day history of dyspnea, fever, pleuritic chest pain, and a nonproductive cough. The patient has acute myeloid leukemia and has undergone induction chemotherapy with resultant prolonged granulocytopenia. She has been hospitalized several times in a building that has several large construction projects in progress. Her last admission was 7 days ago. The patient has worn a mask when in the hospital. Her son has a mild upper respiratory tract infection; other family members are well. All family members received influenza vaccine.

On physical examination on admission, temperature is 39 °C (102.2 °F), pulse rate is 112/min, respiration rate is 24/min, and blood pressure is 118/62 mm Hg. Fine crackles are heard. There are no skin lesions. The leukocyte count is 1000/µL (1.0 × 109/L) with 50% neutrophils, and routine blood chemistry studies are normal. A chest radiograph shows a wedge-shaped infiltrate in the left lower lobe. A CT scan shows that the opacity appears to have a œhalo sign.

Which of the following pathogens is most likely causing this patient's acute findings?

A Legionella pneumophila
]] B Varicella virus
C Candida albicans
D Influenza A virus
E Aspergillus fumigatus

[ArchivalUser]

EE
ASPERGILLOSIS

[ArchivalUser]

EEE

[ArchivalUser]

Correct Answer = E)
Key Points

* Immunosuppressed patients are at increased risk for developing nosocomial pneumonia even when mechanical ventilation is not required.
* A œhalo sign (a nodular lesion with a surrounding ground-glass appearance) on chest radiographs is characteristic of Aspergillus pneumonia.

Immunosuppressed patients are at increased risk of developing nosocomial pneumonia, even when mechanical ventilation is not required. The pneumonia is most often caused by inhalation of aerosols or droplets contaminated with Legionella species, Aspergillus species, respiratory syncytial virus, or influenza virus. The clinical presentation includes fever, headache, myalgias, diarrhea, and cough. Respiratory insufficiency, sepsis, and multi-system organ failure may develop and may lead to death. Initial findings in patients with these infections tend to be similar. However, this patient most likely has an Aspergillus infection because only this organism causes a œhalo sign (a nodular lesion with a surrounding ground-glass appearance) on chest radiographs. Her pleuritic chest pain and fever also support this diagnosis. Aspergillus fumigatus infection occurs most often, but infections due to A. flavus and A. terrus have also been reported.

Legionella pneumophila is also associated with construction and cannot be ruled out completely at this time. However, L. pneumophila pneumonia tends to occur in clusters, is associated with warmer weather, most often causes a lobar pneumonia and gastrointestinal symptoms, and would not induce a halo sign. Varicella (chickenpox) presents with a vesicular rash in various stages of development, and this patient does not have any skin lesions. Candida species rarely cause pneumonia. Influenza A virus causes both upper and lower respiratory tract disease that can be serious in immunosuppressed patients. However, this patient has no epidemiologic risk factors for influenza, and this virus would not cause her radiographic findings.
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