Which of the following is an AIDS-defining illness?

• A. Candidiasis of the mouth
• B. Bacterial pneumonia
• C. Pneumocystis jirovecii pneumonia
• D. Influenza

Answer: (C)

An AIDS-defining illness is an infection or cancer that signals progression to AIDS in someone with HIV. Pneumocystis jirovecii pneumonia is a classic AIDS-defining opportunistic infection because it tends to occur only when the immune system is severely compromised (low CD4 count). Its hallmark presentation includes progressive shortness of breath, dry cough, fever, and hypoxemia, and it requires specific treatment and often hospitalization. Oropharyngeal candidiasis occurs with HIV at various stages and is not by itself an AIDS-defining illness, whereas bacterial pneumonia and influenza can affect people with normal immune function as well.