**Question:** CMV retinitis in HIV patient is seen when CD4 count is -

A. 250-500 cells/mm³
B. 500-1000 cells/mm³
C. 1000-2000 cells/mm³
D. 2000-3000 cells/mm³

**Core Concept:** CD4 cells, also known as T-helper cells, play a crucial role in immune system regulation and defense against infections. CMV (Cytomegalovirus) is a common herpesvirus that can cause opportunistic infections in immunocompromised patients, particularly those with human immunodeficiency virus (HIV) infection or undergoing immunosuppressive therapy.

**Why the Correct Answer is Right:** CMV retinitis is a severe ocular complication of HIV infection. It primarily affects individuals with a low CD4 count, as their immune system is compromised and cannot effectively control the virus. The correct answer refers to the CD4 count range where the risk of CMV retinitis is significantly high.

**Why Each Wrong Option is Incorrect:**

A. CD4 counts in this range may lead to opportunistic infections, but they are not as low as those in the correct answer. Therefore, this option is too high.

B. This range is slightly higher than the correct answer, making it too high for the risk of CMV retinitis to occur.

C. While HIV patients with CD4 counts in this range may still develop opportunistic infections, this range is considered higher than the optimal range for CMV retinitis development.

D. This option is higher than the optimal range for CMV retinitis development, making it incorrect.

**Clinical Pearl:** CD4 count monitoring is essential in HIV-infected patients to identify a steady decline, which may indicate progression to AIDS and the need for antiretroviral therapy. Early intervention is crucial to prevent life-threatening opportunistic infections, including CMV retinitis.

**Correct Answer:** C. CD4 counts <100 cells/mm³ **Explanation:** A CD4 count <100 cells/mm³ is associated with a significantly increased risk of opportunistic infections, including CMV retinitis. HIV patients with CD4 counts below this range are considered immunocompromised and are at higher risk for developing life-threatening opportunistic infections, such as CMV retinitis.