## Clinical Scenario: CMV Retinitis The patient presentation—immunocompromised (CD4 <50), hemorrhagic retinitis with granular opacification—is pathognomonic for **cytomegalovirus (CMV) retinitis**, a serious opportunistic infection in advanced HIV/AIDS. ## Correct Answer Analysis **Key Point:** CMV does NOT integrate its genome into the host chromosome. CMV is a **non-integrating herpesvirus** that establishes latency through **episomal persistence** in infected cells and tissues. ### Latency Mechanisms in Herpesviruses | Virus | Latency Mechanism | Integration | Latency Site | |-------|-------------------|-------------|---------------| | HSV-1/2 | Episomal (circular DNA) | No | Sensory ganglia | | VZV | Episomal | No | Dorsal root ganglia | | CMV | Episomal + myeloid cells | **No** | Bone marrow, lymphoid tissue | | EBV | Episomal | No | B lymphocytes | | HHV-6/7 | Episomal | No | T lymphocytes | | HHV-8 | Episomal + integrated | Possible | Lymphoid cells | **High-Yield:** ~~Retroviruses (HIV) and some DNA viruses (e.g., HPV, HBV)~~ integrate; herpesviruses maintain episomal genomes during latency. ### Verification of Other Statements **Key Point:** Ganciclovir is first-line for CMV retinitis - Intravenous ganciclovir (5 mg/kg IV q12h) is the gold standard - Foscarnet is an alternative for ganciclovir-resistant strains (UL97 or DNA polymerase mutations) - Cidofovir is reserved for resistant cases - Intravitreal injections (ganciclovir implant, foscarnet, cidofovir) for localized disease **Key Point:** CMV transmission routes - Saliva (most common) - Sexual contact - Blood transfusion and organ transplantation - Vertical transmission (congenital CMV) - Respiratory secretions **Clinical Pearl:** CMV seropositivity is >90% in the general population, but disease occurs only with severe immunosuppression (CD4 <50 in HIV). **Key Point:** Immune Recovery Uveitis (IRU) - Occurs 4–12 weeks after immune reconstitution (CD4 >100 cells/μL on ART) - Paradoxical worsening of intraocular inflammation despite viral suppression - Managed with corticosteroids and continuation of ART - Associated with better visual outcomes long-term **High-Yield:** IRU is a form of IRIS—the immune system "sees" viral antigens and mounts an inflammatory response as CD4 count recovers. ```mermaid flowchart TD A[CD4 < 50]:::urgent --> B[CMV Retinitis Risk] B --> C{Immune Reconstitution<br/>CD4 > 100?}:::decision C -->|Yes| D[Immune Recovery Uveitis<br/>IRIS]:::outcome C -->|No| E[Continue Ganciclovir]:::action D --> F[Add Corticosteroids]:::action F --> G[Monitor for Vision Loss]:::outcome ``` [cite:Harrison 21e Ch 172; Robbins 10e Ch 8]
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