Toxoplasmic granuloma within an epiretinal membrane in a patient with recurrent ocular toxoplasmosis

To report the occurrence and pathological confirmation of a granuloma within an epiretinal membrane (ERM) with Toxoplasma gondii tachyzoites in a patient with recurrent retinochoroiditis.

A 54-year-old female patient presented to ophthalmic consultation with decreased visual acuity (VA) and myodesopsia in the right eye (OD). She reported a history of recurrent ocular toxoplasmosis in the OD, treated with sequential courses of oral Folate synthesis inhibitors and anti-inflammatory therapy. Best corrected VA (BCVA) at initial examination was 20/400 in OD and 20/20 in OS. Fundus examination in OD revealed multiple white retinal lesions, superior to the superior temporal vessels, and temporal to the macula. OCT of the macular area showed cystoid macular edema and a thick ERM. The patient was initiated on TMP-SMX (160 mg/800 mg/day), azithromycin (250 mg/day), meprednisone (40 mg/day) and folinic acid. The BCVA improved to 20/40 after 45 days of treatment. Following initial treatment suspension, the BCVA decreased to 20/60. Given the extent of retinal fibrosis and architectural disruption of the retina by ERMs a vitrectomy was scheduled. ERMs were successfully peeled, and silicone tamponade was performed. Pathology results revealed the presence of a granuloma within the ERM. Immunohistochemistry confirmed the presence of T. gondii tachyzoites within the granuloma.

The presence of T. gondii organisms within a granuloma confined to the ERM may have biological and therapeutic implications. ERM may act as a barrier, protecting the parasite from systemically delivered drugs that rely on vascular access to the lesion.