Cytomegalovirus retinitis

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Cytomegalovirus retinitis is a late complication of cytomegalovirus (CMV) infection, usually occurring in immunosuppressed patients. It is an acquired immune deficiency syndrome (AIDS) defining illness.

Epidemiology

The reported incidence and prevalence of CMV retinitis varies with geographical location. The prevalence in patients with AIDS in Africa and China is reported at 0-8.5% and 7.5% respectively. However, the prevalence in Singapore is reported at 0.125% . A possible explanation for these findings include the availability of active screening in patients with AIDS.

CMV retinitis tends to occur in patients that cannot generate a T cell response against CMV. The highest incidence is observed in patients with AIDS and immunosuppression for organ transplantation (including bone marrow transplantation).

Interestingly, the initiation of antiretroviral therapy in patients with CMV retinitis can cause a paradoxical increase in symptoms of up to 40% of patients due to T cell response against dead CMV virus .

Clinical presentation

CMV retinitis tends to manifest with CD4 counts of <50 cells/mm. Approximately 50% of patients have bi-ocular involvement .

The symptoms may include:

  • presence of floaters in the vision
  • decreased vision
  • photophobia

Ocular findings may include:

  • retinal vessel vasculitis
  • chorioretinitis
  • retinal (including macular) inflammation to varying degrees

The diagnosis of CMV retinitis is made with ophthalmic examination and the presence of CMV IgG. The diagnosis is made with fundus photographs and optical coherence tomography.

Radiographic features

Although the diagnosis is generally clinical, bedside ultrasound may be helpful in cases where retinal detachment is suspected .

Additionally, MRI and CT brain may show the presence of concurrent CMV encephalitis.

Treatment and prognosis

The treatment for CMV retinitis involves administration of antiviral medications (e.g. valganciclovir, ganciclovir, foscarnet, or cidofovir). In one study, it was found that the mortality rate for patients with CMV retinitis was 28% .

Practical points

  • in immunosuppressed or immunocompromised patients suspect CMV as a cause of retinitis if patients complain of new onset visual disturbances
  • bedside ultrasound may serve as a good initial test to screen for possible retinal detachment
  • further follow-up with ophthalmic imaging will be required