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CMV Retinitis

URGENT — Retina

Symptoms

  • Progressive unilateral or bilateral vision loss.
  • New floaters or "blind spots" (scotomas).
  • Often asymptomatic in early peripheral disease; high-risk patients require routine screening.

Clinical Findings

Classic triad ("pizza fundus")

  • Retinitis: White, granular, full-thickness retinal necrosis.
  • Hemorrhage: Scattered "brushfire" hemorrhages within or at the leading edge of necrosis.
  • Mild Vitritis: Usually minimal in severely immunosuppressed patients.

Progression & anatomy

  • Expansion: Necrosis typically follows vascular arcades, advancing at ~250 µm/week.
  • Frosted-branch angiitis: Intense perivascular sheathing occasionally seen in active disease.
  • Zone 1: Involvement within 3000 µm of the fovea or 1500 µm of the optic nerve (highest vision threat).

Chronic & recovery signs

  • Atrophy: Healed lesions leave "burnt-out" atrophic retina with RPE mottling.
  • Retinal Detachment: High risk (30–40%) due to multiple necrotic retinal breaks.
  • Immune Recovery Uveitis (IRU): Increased vitritis, CME, or ERM after starting ART as the immune system reactivates.

Etiology

Host factors

  • Reactivation of latent Cytomegalovirus (CMV) during profound cellular immunodeficiency.
  • Classic setting: AIDS with CD4 count <50 cells/µL.
  • Modern settings: Hematologic malignancies, bone marrow/solid organ transplant, or intensive chemotherapy.

Red Flags

  • CD4 <50 cells/µL: Mandatory dilated fundus exam every 3 months for screening.
  • Zone 1 Lesions: Threaten the fovea or optic disc; require immediate intravitreal therapy.
  • Bilateral involvement: Indicates high systemic viral load and high risk of disseminated CMV disease.
  • Flashes/Floaters in healing phase: High suspicion for CMV-related rhegmatogenous retinal detachment.

Investigations

Clinical assessment

  • Dilated fundus exam with peripheral depressed ophthalmoscopy.
  • Wide-field fundus photography to document lesion borders for progression tracking.

Laboratory testing

  • HIV status and CD4+ T-lymphocyte count.
  • CMV PCR (Aqueous/Vitreous): Diagnostic gold standard if the clinical appearance is atypical.
  • Plasma CMV PCR: Useful for monitoring systemic burden but does not confirm retinitis.

Systemic screening

  • Evaluation for extraocular CMV: GI (colitis), pulmonary (pneumonitis), or hepatic involvement.

Treatment

Systemic therapy (induction & maintenance)

  • Valganciclovir: 900 mg PO BID for 3 weeks (induction), followed by 900 mg daily (maintenance).
  • IV Ganciclovir: 5 mg/kg BID for severe disease or patients with poor GI absorption.
  • Maintenance duration: Continue until CD4 >100 cells/µL for at least 3–6 months on ART.

Intravitreal therapy

  • Indications: Zone 1 disease or failure of systemic therapy.
  • Agents: Ganciclovir (2 mg/0.1 mL) or Foscarnet (2.4 mg/0.1 mL) twice weekly initially.

Surgical intervention

  • Pars plana vitrectomy with silicone oil tamponade for CMV-associated retinal detachment.

Clinical Pearl

"Pizza fundus" (white necrosis + brushfire hemorrhage) in an immunocompromised patient is CMV retinitis until proven otherwise. While oral valganciclovir is the standard, immune reconstitution via ART is the only definitive way to arrest the disease.

Differential Diagnosis

  • Acute Retinal Necrosis (ARN): HSV/VZV; more rapid, peripheral, and associated with severe vitritis.
  • Progressive Outer Retinal Necrosis (PORN): VZV in AIDS; deep retinal whitening with minimal vitritis.
  • Toxoplasmic Retinochoroiditis: Typically focal with an adjacent pigmented scar.
  • Syphilitic Chorioretinitis: "The Great Masquerader"; usually multifocal or placoid.
  • Primary Intraocular Lymphoma: Creamy sub-RPE infiltrates in older patients.

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