Pulmonary Infections in Immunocompromised Patients

Primary Infectious Considerations

PCP characteristically presents with diffuse bilateral perihilar infiltrates and patchy areas of ground-glass attenuation with peripheral sparing, particularly in patients with risk factors for immunosuppression, including chronic HCV infection and history of drug use 1
The American College of Physicians recommends considering PCP in patients with upper lobe predominance, although it is atypical, especially with cystic changes 1
Atypical pneumonia, including Mycoplasma and Chlamydia, can present with ground glass opacities, and testing for these pathogens via respiratory nucleic acid detection is recommended 2
Tuberculosis and nontuberculous mycobacterial infections must be considered in patients with a history of drug use and upper lobe predominance, with nodular or cavitary lesions suggestive but not always present early 1

The Centers for Disease Control and Prevention recommends assessing for HIV status, as it is critical in HCV/drug use population, and PCP becomes most likely if CD4 <200 1
Checking for fever, hypoxemia severity, and lymphocyte count is essential, as lymphopenia suggests PCP or viral infection 2, 4

The Infectious Diseases Society of America recommends starting trimethoprim-sulfamethoxazole 15-20 mg/kg/day immediately if PCP is strongly suspected, and adding prednisone if PaO2 <70 mmHg or A-a gradient >35 mmHg 1
Initiating respiratory isolation and considering empiric anti-TB therapy pending cultures is recommended if TB is suspected based on upper lobe cavitation or high endemic risk 1