Cytomegalovirus (Cmv) Retinitis

Description

Cytomegalovirus is a double-stranded DNA herpesvirus to which most individuals are exposed by early adulthood. It seldom produces clinical illness in healthy individuals. Patients with poor immune function, however, are liable to reactivation of CMV virus in multiple organs including the retina. CMV retinitis occurs almost exclusively in immunocompromised patients, such as with HIV/AIDS. The typical presentation is with a slowly-progressive, hemorrhagic necrotizing retinitis in patients with CD4+ lymphocyte counts below 50 cells/mm3.

Symptoms

The most common symptoms are progressive, painless blurring or loss of vision with floaters in one or both eyes. A minority of patients – particularly with peripheral retinal involvement – are asymptomatic.

Signs

CMV retinitis is bilateral in up to half of cases. Two patterns are recognized, although both patterns may co-exist in the same patient:
Indolent/’brushfire’: peripheral granular opacities with little or no associated hemorrhage.
Fulminant: confluent, pale patches of necrotic retina with associated hemorrhage, resembling a ‘pizza pie’ or ‘cheese and ketchup’. The infection tends to progress along the major retinal blood vessels, which may also become inflamed and appear sheathed. The optic nerve is occasionally involved. There is typically minimal vitreous inflammation, in contrast with the more rapidly-progressive necrotizing herpetic retinopathy.
Resolution of active inflammation leaves behind retinal pigment epithelium (RPE) atrophy and clumping. The damaged retina is liable to develop retinal breaks and subsequent retinal detachment, which may require surgery. Without treatment or improvement in the host’s immune system, CMV retinitis is a slowly-progressive but relentless infection which eventually causes blindness.

Incidence

CMV retinitis is the most common opportunistic ocular infection in patients with AIDS.

Significance

The leading cause of HIV/AIDS-related blindness.

Differential Diagnosis

AIDS Retinopathy, Necrotizing Herpetic Retinopathies, Syphilis, Toxoplasmosis.

See Also

See Also

Additional Investigations

Retinal detachment – Rhegmatogenous.

Management

Imaging

The diagnosis of CMV retinitis is usually clinical. Because the disease usually spreads slowly, serial examination and fundus photography may be appropriate

Blood tests, microbiology, pathology

Since most patients susceptible to CMV retinitis will carry the CMV in bodily fluids, the diagnostic value of blood or urine microbiological tests is questionable. PCR (polymerase chain reaction) testing on aqueous or vitreous fluid may be useful in cases where the diagnosis is uncertain

Systemic Medications

Treatment of CMV retinitis is tailored to disease severity and the patient’s immune and other organ function. Induction and maintenance regimes are administered. Induction therapy usually achieves disease stabilization within 2 weeks. Since anti-CMV medications do not eradicate CMV infection in persistently immunocompromised patients, maintenance therapy is required indefinitely. Eventually, recurrent retinitis is expected despite maintenance therapy in these patients. Relapse does not necessarily imply drug resistance, and is often managed with repeat induction therapy. Medications are changed in cases of drug resistance or prohibitive adverse drug reactions.

Topical medications

Some patients who achieve remission of CMV retinitis are susceptible to immune-recovery uveitis, which may be confused with reactivation of CMV retinitis. Clinical features include uveitis with anterior chamber or vitreous infiltrates, cystoid macular edema, epiretinal membrane formation, neovascularization and cataract. Corticosteroid therapy is often effective, and does not appear to cause reactivation of CMV retinitis.

Referral & review

Management of immunocompromised patients is multidisciplinary. When the underlying disease is not known, HIV testing and referral to an infectious diseases physician is indicated.
Patients with active CMV retinitis require review at least monthly. Since active retinitis may be asymptomatic, patients with CD4+ counts below 50 cells/mm3 without active retinitis should be reviewed at least every 3 months.