Sir,

Cytomegalovirus retinitis (CMVR) is an AIDS-defining diagnosis, and typically occurs when CD4 counts fall below 50 cells per μl.1 We report an unusual case of CMVR in a patient whose CD4 counts never decreased below 250 cells per μl.

Case report

A 30-year-old man was diagnosed with HIV infection 3 years ago, and CD4 counts remained between 600 and 700 cells per μl since diagnosis. After 2 years, his counts decreased from 565 to 426 cells per μl over 3 months. Antiretroviral therapy (ART) consisting of tenofovir/emtricitabine and efavirenz was commenced. Three months later, he complained of right eye blurring with floaters. Vision was 6/9 and fundoscopy revealed active CMVR, corroborated on aqueous PCR for CMV (Figure 1). His CD4 count was 254 cells per μl and HIV viral load was 42 593 copies per ml that increased to 165 800 copies per ml 2 weeks later. He had no other AIDS-defining illnesses.

Figure 1
figure 1

Nine-view fundus photograph of the patient's right eye, showing both superotemporal and active CMV retinitis involving 40% of inferior retina.

Full size image

Comment

CMVR is a late manifestation of AIDS when CD4 counts are <50 cells per μl. Although reports have documented cases in patients with CD4 counts >100 cells per μl at time of diagnoses, they had low CD4 counts before diagnosis of CMVR, before or following ART.2 Our case is unique that CD4 counts before the diagnosis of CMVR had never decreased below 254 cells per μl.

Postulated reasons for the lack of correlation between CD4 counts and occurrence of CMVR include the functional dysfunction of CD4 T cells in AIDS. Although there is high correlation between counts and function, CD4 counts are a surrogate marker for immune dysfunction and do not reflect functional abnormalities in the immune system.3 Initial increment in CD4 counts after ART may be because of systemic redistribution of memory non-specific T lymphocytes, whereas the actual increase in CMV-specific T cells occurs later. CMVR may occur during this latent period between quantitative restoration of CD4 counts and actual functional restoration of immunity. Moreover, clonal deletions of CMV-specific T lymphocytes can occur, impairing immunity against CMV, while maintaining overall high CD4 counts.

In addition to absolute CD4 counts, CMVR may be correlated with other predictive factors; for example, rapid decline in CD4 counts by >100 cells per μl after diagnosis of CMVR,1, 3, 4 high HIV viral loads >100 000 copies per ml, and presence of CMV viremia.5 Other risk predictors, such as trends in CD4 counts and viral load should also be considered. Therefore, the clinical diagnosis of CMVR should not be dismissed in the presence of a normal CD4 count.