CMV retinitis risk in AIDS patients falls below which threshold CD4 count?

• A. <100
• B. <50
• C. <200
• D. <350

Answer: (B)

CMV retinitis is a problem that appears when cell-mediated immunity is severely impaired, as seen in AIDS. The level at which risk becomes substantial is when the CD4 count drops below about 50 cells per microliter. Below this threshold, CMV can reactivate and cause retinal disease, so surveillance and prophylaxis considerations are most critical. Counts above 50 have a much lower risk, even though risk gradually increases as CD4 numbers fall further. The other values reflect thresholds used for different opportunistic infections, not the specific point at which CMV retinitis risk rises.