A 36-year-old man with AIDS presents with floaters and visual loss. Fundus shows dense yellow-white retinal necrosis with granular borders and haemorrhage along the edges, following the vascular arcades, with minimal vitritis. His most recent CD4 count was 28 cells/mm3. The causative agent is:

• A Cytomegalovirus ✓
• B Varicella zoster virus
• C Toxoplasma gondii
• D Treponema pallidum

Explanation

CMV retinitis occurs almost exclusively when the CD4 count falls below 50 cells/mm3 and produces full-thickness necrotising retinitis with haemorrhagic borders, classically described as pizza pie or ketchup and cheese appearance, with little inflammation because of immunosuppression. VZV causes ARN with heavy vitritis in immunocompetent patients, toxoplasma gives focal lesions adjacent to scars, and syphilis produces panuveitis rather than this picture.

Reference: Ryan's Retina, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.