A patient with HIV and cavitary lesions on a chest x-ray is placed on airborne precautions. Which diagnosis is most likely?

• A. M. tuberculosis infection
• B. Pneumocystis jirovecii pneumonia
• C. Histoplasmosis
• D. Varicella zoster virus infection

Answer: (A)

Cavitary lesions in the lungs, especially in the upper lobes, point toward reactivation tuberculosis. In people with HIV, the weakened cell-mediated immunity makes TB reactivation more likely, and the disease often shows focal cavitation on imaging. Because TB is spread through airborne droplet nuclei, airborne precautions are essential to prevent transmission, even before confirmatory tests. Other HIV-associated pneumonias tend to present with different radiographic patterns—Pneumocystis jirovecii pneumonia usually shows diffuse interstitial or alveolar infiltrates rather than cavitation; histoplasmosis can mimic TB at times but cavitation is less classic; Varicella zoster virus pneumonia is not typically cavernous. So the most likely diagnosis given the cavitary pattern and the need for airborne precautions is tuberculosis.