Asymptomatic cytomegalovirus infections, which are widespread in most communities, are transmitted congenially, by sexual contact or by blood transfusion. The primary infection may present as a mononucleosis-like syndrome which soon resolves. Most people then remain latently infected but asymptomatic for life. Primary infection is thought to be rare in HIV as most have been exposed to CMV prior to their HIV infection. CMV disease occurs when a previously latent CMV infection is activated, usually when a patient becomes profoundly immunosuppressed such as in advanced HIV disease. It then causes clinical ‘end organ’ disease, most commonly CMV retinitis, but also, oesophagitis, encephalitis, myelitis, radiculopathy, colitis and rarely a pneumonitis.

The main symptoms of CMV retinitis include; floaters, blurred vision, reduced visual field, and flashing lights/sparks. Even subtle changes, such as minor loss of peripheral vision, can indicate the development of CMV retinitis. There is usually no pain involved. Clinical manifestation of progressive CMV retinitis include flame-shaped intraretinal haemorrhages superimposed on white granular necrotic patches in the fundi. If treatment is not given CMV retinitis results in loss of vision.

CMV disease of other organs is diagnosed by biopsy where histology will reveal typical round intranuclear inclusions, in swollen cells.

Treatment is required following detection of CMV end organ disease, otherwise it will progress rapidly. In CMV retinitis, treatment for 14 to 21 days is required followed by lifelong maintenance therapy to prevent relapse. With other forms of CMV disease treatment can be for either a specified course (CMV colitis) or until symptoms have resolved or ulcers have healed (CMV oesphagitis). Maintenance therapy is not routinely given. Despite being on maintenance therapy, most patients with CMV retinitis will relapse and reinduction with intravenous therapy will be required.

Both ganciclovir and foscarnet are extremely toxic and close monitoring is required. Oral ganciclovir achieves lower plasma levels then the IV formulation, which has the advantage that toxicity is reduced, but can fail to control the CMV retinitis. Patients should be told to take the ganciclovir capsules with food to obtain maximal bioavailability.