Cytomegalovirus (CMV) retinitis is a severe opportunistic infection that primarily affects immunocompromised individuals, including those with advanced HIV/AIDS, organ transplant recipients, and patients undergoing immunosuppressive therapy. This retinal infection can lead to irreversible vision loss if not diagnosed and treated promptly.
Pathophysiology of CMV Retinitis
CMV is a member of the herpesvirus family and remains latent in the body after primary infection. In immunocompromised patients, viral reactivation leads to widespread endothelial cell infection, inflammation, and retinal necrosis. The virus spreads through the retina via direct cell-to-cell transmission, causing progressive retinal destruction.
Causes and Risk Factors
CMV retinitis occurs primarily in patients with weakened immune systems. The major risk factors include:
- HIV/AIDS: Particularly when CD4+ T-cell counts drop below 50 cells/µL.
- Organ Transplantation: Use of immunosuppressive drugs increases susceptibility.
- Cancer Patients: Those undergoing chemotherapy or bone marrow transplantation.
- Long-term Corticosteroid Therapy: Reduces immune response, facilitating viral reactivation.
Clinical Presentation and Symptoms
The onset of CMV retinitis can be insidious or rapid, depending on immune status. Key symptoms include:
- Floaters: Patients may notice small dark spots in their vision.
- Blurred Vision: Progressive loss of clarity in central or peripheral vision.
- Photopsia: Sensations of flashing lights due to retinal involvement.
- Scotomas: Dark spots or blind spots in the field of vision.
- Painless Vision Loss: A hallmark symptom that distinguishes it from other retinal infections.
Diagnosis of cmv retinitis in immunocompromised patient
Early and accurate diagnosis is crucial for effective management. Diagnostic methods include:
Ophthalmologic Examination
- Fundoscopic Examination: Identifies characteristic retinal findings such as yellow-white infiltrates, hemorrhages, and perivascular necrosis.
- Optical Coherence Tomography (OCT): Assesses retinal thickness and structural integrity.
- Fluorescein Angiography: Evaluates retinal blood flow and areas of ischemia.
Laboratory and Molecular Tests
- Polymerase Chain Reaction (PCR): Detects CMV DNA in blood, aqueous humor, or vitreous fluid.
- CMV Antigenemia Test: Identifies CMV-specific proteins in blood samples.
Treatment Options for CMV Retinitis
Prompt initiation of antiviral therapy is necessary to prevent disease progression and vision loss.
First-Line Antiviral Therapies
- Ganciclovir (IV or intravitreal): Effective but requires close monitoring due to bone marrow suppression.
- Valganciclovir (oral): Preferred for maintenance therapy due to better systemic bioavailability.
- Foscarnet: Used in ganciclovir-resistant cases; nephrotoxic.
- Cidofovir: Long half-life but associated with nephrotoxicity and uveitis.
Intravitreal Injections
- Direct injection of ganciclovir or foscarnet into the vitreous humor provides high local drug concentrations while reducing systemic toxicity.
Adjunctive Therapies
- Highly Active Antiretroviral Therapy (HAART): Essential for HIV patients to restore immune function and reduce recurrence.
- Corticosteroids: Used cautiously to control immune recovery uveitis (IRU) in patients initiating HAART.
Prognosis and Complications
With effective treatment, disease progression can be halted, but vision loss may be irreversible if retinal damage is extensive. Common complications include:
- Retinal Detachment: Occurs in 30-40% of cases due to extensive necrosis.
- Optic Atrophy: Permanent damage to the optic nerve leading to blindness.
- Immune Recovery Uveitis: Inflammatory response in patients starting HAART, causing secondary vision impairment.
Prevention Strategies
- Routine Screening: Regular fundoscopic exams for high-risk patients.
- Preemptive Antiviral Therapy: Considered in transplant recipients with high CMV viral loads.
- Optimized Immunosuppression: Balancing immune suppression while minimizing infection risk.
