**Question:** Chorioretinitis in AIDS is caused by

A. Herpes simplex virus (HSV)
B. Cytomegalovirus (CMV)
C. Toxoplasma gondii
D. Varicella-zoster virus (VZV)

**Core Concept:** AIDS, or Acquired Immunodeficiency Syndrome, is a severe condition caused by the Human Immunodeficiency Virus (HIV) that attacks and destroys CD4+ T cells, impairing the immune system. Chorioretinitis is a type of inflammation affecting the choroid (a layer in the eye) and retina, which may lead to vision problems and blindness.

**Why the Correct Answer is Right:** Chorioretinitis in AIDS is primarily caused by Toxoplasma gondii (Option C). Toxoplasma gondii is a protozoan parasite that can invade the central nervous system and other tissues, including the eye. In AIDS patients with compromised immune systems, the parasite can invade the retina and choroid, resulting in chorioretinitis.

**Why Each Wrong Option is Incorrect:**

A. Herpes simplex virus (HSV) and B. Cytomegalovirus (CMV) are common causes of viral infections, but they are not typically associated with AIDS-related chorioretinitis. These viruses typically cause infections in the skin, mucous membranes, and central nervous system.

C. Varicella-zoster virus (VZV), which causes chickenpox and shingles, is not a common cause of AIDS-related chorioretinitis. It primarily affects immunocompetent patients and is not associated with CD4+ T cell depletion.

**Clinical Pearl:** Toxoplasma gondii is a common cause of chorioretinitis in AIDS patients due to the weakened immune system, leading to opportunistic infections. Early detection and treatment are crucial to prevent vision loss and blindness in these patients.