Pneumocystis jirovecii pneumonia

PCP (now PJP) is an opportunistic infection commonly seen in HIV positive patients with CD4 counts below 200. Ubiquitous in the environment, but it is very uncommon for immunocompetent patients to be infected.

Besides HIV, the other major risk factor is steroid use. In general, after 2 weeks of corticosteroid use at 20mg or more, PCP prophylaxis is indicated.

The classic clinical presentation is subacute onset dyspnea and dry cough. Other signs may include fever, tachycardia, and tachypnea. The chest exam is variable - there may be crackles, but in up to 50% of cases, the respiratory exam is normal.

The chest X-ray often reveals bilateral interstitial infiltrates, but virtually any abnormality may be seen.

Remember that PCP is a classic example of "CXR-negative pneumonia", where the immune reaction necessary to generate an infiltrate is absent. Pneumothorax may complicate PCP (the c is for cysts, which may rupture into the pleural space). Click here for a CXR showing this

Confirmation of diagnosis:
Silver staining of induced sputum (if possible) or BAL specimen (gold standard). PCR is under investigation.


Therapy:

1) TMP-SMX in high doses. In the event of sulfa allergy (interestingly more common in the HIV population), other agents can be used, such as pentamidine, dapsone, or atovaquone.
With high-dose TMP-SMX, look out for hyperkalemia, renal failure, hypoglycemia

2) Steroids for PO2 of 70 or lower or A-a gradient of 35 or higher.

Regimen is a 21-day oral taper of prednisone. The research showing the benefit of steroids in PCP comes from Toronto, and Toronto Western was part of the trial.


Other links:

Click here for the paper discussed by Marrie et al on "atypical pneumonia" and how clinical features do not reliably distinguish "typical" from "atypical" organisms.

SPECIAL NOTE:
Please click here for a Globe and Mail article about our very own Dr. Ho Ping Kong and his legendary morning report!