When a CD4 count drops below 50 cells/mcL, which opportunistic infection are patients most prone to developing?

When a CD4 count drops below 50 cells/mcL, patients are particularly at risk for developing infections from Mycobacterium avium complex (MAC). This is primarily due to the severely compromised immune system associated with such low CD4 counts, which significantly reduces the body’s ability to mount an effective immune response against various pathogens.

Mycobacterium avium complex is a group of bacteria that includes Mycobacterium avium and Mycobacterium intracellulare, which are commonly found in the environment, particularly in water, soil, and dust. In immunocompromised patients, especially those with advanced HIV/AIDS, MAC can lead to disseminated infection, causing symptoms like fever, weight loss, and gastrointestinal issues.

While other opportunistic infections are also a concern at low CD4 counts, MAC is specifically known to occur more frequently when CD4 counts are very low, making it a hallmark infection in this context. Consequently, awareness and prophylactic treatment against MAC become critical for managing patients with such low CD4 counts.