Ocular toxoplasmosis may be familiar territory for ophthalmologists, but systemic immunocompromise can substantially alter its clinical course. A new review in Progress in Retinal and Eye Research suggests that Toxoplasma gondii behaves as a particularly aggressive ocular pathogen in this population, with atypical presentations frequently complicating diagnosis and contributing to poor visual outcomes.
Elke Kreps and colleagues reviewed the literature on ocular toxoplasmosis in patients with systemic immunocompromise, including people with HIV, transplant recipients, patients taking immunomodulatory therapies, those with malignancies, and people with primary immunodeficiencies. Their search identified 133 relevant articles, including 109 reports containing clinical data from 276 immunocompromised patients and 345 affected eyes. HIV infection was the most common cause of immunocompromise, accounting for 60.9 percent of the cases.
The findings underline just how differently ocular toxoplasmosis can behave when immunity is impaired. Visual disturbance, including blurred vision and floaters, was reported in 91.8 percent of eyes with available symptom data. More strikingly, 76.4 percent of eyes with reported presenting acuity were 6/15 or worse, while 55.7 percent were 6/60 or worse. Eight eyes had no light perception at presentation.
Clinical appearance was also highly variable. Although the classic white necrotizing retinitis adjacent to a pigmented retinochoroidal scar can occur, immunocompromised patients often presented without pre-existing scars. Lesions also showed a tendency to involve the posterior pole, with macular or peripapillary involvement reported in 77.4 percent of eyes for which location was available.
Multifocal disease emerged as another important feature. Whereas immunocompetent adults typically develop a single focus of active retinitis, 41.3 percent of eyes in the review had multifocal lesions. Lesions could also be unusually large or diffuse, sometimes mimicking acute retinal necrosis or cytomegalovirus retinitis – a potential diagnostic trap in an already complex patient population.
This diagnostic uncertainty appears to have real consequences. The review authors report that the initial diagnosis was missed in more than half of published cases with sufficient clinical information. They therefore highlight molecular analysis of ocular fluid as particularly important when the presentation is atypical.
Management also differs from that in immunocompetent patients. Because retinal lesions in immunocompromised individuals may continue enlarging without treatment, the review considers any active toxoplasmic retinal lesion an indication for systemic antiparasitic therapy. Treatment regimens varied widely, although pyrimethamine plus sulfadiazine was the most commonly reported combination.
The reviewemphasizes that in an immunocompromised patient, ocular toxoplasmosis may lack its textbook appearance, progress aggressively and imitate other infectious retinitides. Early recognition, appropriate molecular testing and prompt antiparasitic therapy may therefore be critical to preserving vision. Additionally, the authors suggest that “routine immune status stratification in clinical studies could further enhance understanding of how various forms of immunodeficiency affect the clinical presentation of, and the diagnostic and therapeutic approaches to, ocular toxoplasmosis.”
