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Laboratory science
Bilateral retinochoroiditis caused by an atypical strain of Toxoplasma gondii

Abstract

Background: A 53-year-old man presented with an acute bilateral posterior uveitis with extensive necrotising retinochoroiditis but without chorioretinal scarring. A thorough workup did not reveal any underlying disease. The possibilities of atypical ocular toxoplasmosis as well as herpetic retinal necrosis were considered and specific therapy instituted, with little improvement. The patient died within 2 months as result of an undifferentiated squamous cell carcinoma.

Methods: Histopathological examination, immunohistochemistry and multilocus polymerase chain reaction confirmed Toxoplasma gondii infection of the retina

Results: Macroscopic examination of enucleated globe showed extensive retinal necrosis and vitreous detachment. Histological examination of retinal tissue identified numerous round-to-elliptical toxoplasmic cysts within the retina, with retinal necrosis and minimal choroidal inflammation. Immunohistochemical analyses confirmed that the cysts were due to T gondii. DNA extracted from formalin-fixed, paraffin-embedded tissue sections was subjected to multilocus polymerase chain reaction (PCR) analysis at the following typing loci: SAG1, SAG2, SAG3, SAG4, B1, NTS2, GRA6 and GRA7. DNA sequencing of positive PCR products at the NTS2, SAG1 and GRA7 loci confirmed the presence of a non-archetypal strain of T gondii infecting the eye of the patient experiencing a severe, atypical ocular toxoplasmosis

Conclusion: A highly divergent, non-archetypal strain of T gondii was responsible for causing a severe, atypical bilateral retinochoroiditis in a patient from Brazil.

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