Final answer:
Pneumocystis pneumonia (PCP) is a severe infection caused by Pneumocystis jirovecii in immunocompromised patients, and chemoprophylaxis such as TMP/SMZ is recommended when CD4 counts drop below 200 cells/µL.
Step-by-step explanation:
Pneumocystis Pneumonia and Immunocompromised Patients
Pneumocystis pneumonia (PCP) is a serious infection caused by the fungus Pneumocystis jirovecii. This type of pneumonia is particularly concerning in immunocompromised individuals, such as those taking high-dose immunosuppressants or patients with AIDS. A chest X-ray (CXR) showing diffuse bilateral ground glass infiltrates in a febrile patient is suggestively diagnostic of PCP, particularly in the context of immune suppression. Prophylaxis against PCP is recommended when CD4 counts drop below a certain threshold. For patients with HIV/AIDS, chemoprophylaxis with medications such as trimethoprim-sulfamethoxazole (TMP/SMZ) is generally initiated when CD4 counts fall below 200 cells/µL.
Given the clinical scenario described, if a patient taking high dose immunosuppressants shows signs of PCP, it is essential that prompt medical treatment with appropriate therapeutics like TMP/SMZ is initiated alongside further diagnostic tests, including direct immunofluorescence assay (DFA), and, if warranted, PCR-based tests to confirm the presence of P. jirovecii.