PCP is a common respiratory opportunistic infection in HIV+ individuals. Those with a CD4 count less than 200 are at the greatest risk. It is a protozoa, and is found ubiquitously in soil - we are all exposed, but this organism poses few problems to healthy immune systems.The classic clinical presentation is dyspnea with subacute onset, and a dry cough. Patients may have a low-grade fever, tachycardia, and tachypnea. The chest exam is variable - you may hear crackles...you may have a normal exam (in up to 50% of cases). The Chest X-ray often reveals bilateral interstitial infiltrates, but virtually any abnormality may be seen.
Remember, we can make the diagnosis roughly 90% of the time with history and physical exam alone. Still, it is nice to confirm your diagnosis by politely acknowledging the presence of an organism. Methenamine silver (photo above) or Immunofluorescent (photo below) stains on induced sputum (or bronchoalveolar lavage) has a high sensitivity and specificity.
Treatment: TMP-SMX in high doses. This has some interesting complications associated with it. If people are allergic to sulfa drugs or have complications, other agents can be used, such as TMP-Dapsone, or Atovaquone.
Steroids? Yep. If the PaO2 is less than 70, this is very helpful. Of note, this was a major breakthrough in medicine and was discovered here at the Toronto Western Hospital.
What else? Watch these patients closely. There is often a profound inflammatory reaction to the dying organisms, and patients often get worse on day 2-ish of treatment. That is why the steroids are added in severe disease.
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