A 32-year-old man with newly diagnosed HIV (CD4 count 45 cells/μL) presents with floaters, photopsia, and progressive visual field loss over 2 weeks. Fundoscopic examination reveals hemorrhagic retinitis with granular, hemorrhagic infiltrates in the periphery advancing centripetally in a 'cottage cheese and ketchup' pattern. Anterior chamber is quiet. What is the most likely diagnosis and the immediate management?

Explanation

## Clinical Diagnosis: CMV Retinitis in Advanced AIDS **Key Point:** CMV retinitis is the most common opportunistic ocular infection in patients with CD4 <50 cells/μL. The 'cottage cheese and ketchup' appearance (hemorrhagic infiltrates with granular borders) is pathognomonic. **Clinical Pearl:** The quiet anterior chamber (minimal inflammation) is a key distinguishing feature of CMV retinitis—it is primarily a viral infection of the retina without significant immune response, unlike ARN (acute retinal necrosis) which shows vitritis. **High-Yield:** CMV Retinitis Features: - CD4 threshold: <50 cells/μL - Presentation: floaters, photopsia, visual field defects (often asymptomatic initially) - Fundoscopy: hemorrhagic or granular infiltrates; centripetal progression - Anterior chamber: quiet (no vitritis) - Prognosis: progressive retinal necrosis and detachment if untreated ## Differential Diagnosis of Retinitis in AIDS | Condition | CD4 Threshold | Vitritis | Infiltrate Pattern | Management | | --- | --- | --- | --- | --- | | CMV retinitis | <50 | Minimal/absent | Hemorrhagic, granular, centripetal | IV ganciclovir/foscarnet + ART | | ARN (HSV/VZV) | <50–100 | Severe | Granular, full-thickness necrosis, centrifugal | IV acyclovir, intravitreal foscarnet | | Progressive outer retinal necrosis (PORN) | <50 | Minimal | Granular, outer retina, rapid | IV acyclovir, intravitreal foscarnet | | Immune recovery uveitis (IRU) | CD4 recovery | Moderate–severe | Granular infiltrates + vitritis | Corticosteroids, NSAIDs | **Mnemonic:** CMV = **C**D4 <50 = **M**inimal vitritis = **V**iral retinitis (cottage cheese & ketchup) ## Management Algorithm ```mermaid flowchart TD A[CMV Retinitis Suspected]:::outcome --> B{CD4 count?}:::decision B -->|<50| C[Confirm with dilated fundoscopy]:::action C --> D[Start IV Ganciclovir 5 mg/kg BD]:::action D --> E[Initiate/optimize ART immediately]:::action E --> F[Monitor for immune recovery uveitis]:::action B -->|>50| G[Unlikely CMV; consider other diagnosis]:::outcome F --> H{CD4 >100 sustained?}:::decision H -->|Yes| I[Taper ganciclovir; monitor]:::action H -->|No| J[Continue maintenance ganciclovir]:::action ``` **Warning:** Do NOT confuse CMV retinitis with acute retinal necrosis (ARN). ARN presents with severe vitritis, full-thickness retinal necrosis, and centrifugal spread—it requires IV acyclovir and intravitreal foscarnet, not ganciclovir. ARN can occur at higher CD4 counts (>100) and is caused by HSV-1/2 or VZV.