Vision-threatening ocular toxoplasmosis involving the fovea diagnosed by intraocular fluid mNGS: A case report.

Ocular toxoplasmosis is the most common cause of infectious posterior uveitis worldwide and may lead to irreversible visual impairment when the macula is involved. Definitive diagnosis remains challenging because clinical manifestations overlap with those of other infectious and inflammatory retinal disorders. We report a case of active ocular toxoplasmosis involving the fovea in an immunocompetent 44-year-old man presenting with progressive unilateral visual loss and central scotoma. Ophthalmic examination revealed keratic precipitates, mild vitritis, and a yellow-white inflammatory lesion involving the macular region. Fluorescein angiography demonstrated progressive hyperfluorescent staining, and optical coherence tomography showed a hyperreflective subfoveal lesion. Serological testing was positive for anti-Toxoplasma gondii IgM and IgG antibodies. Intraocular fluid analysis demonstrated positive anti-Toxoplasma IgG, while metagenomic next-generation sequencing (mNGS) directly identified Toxoplasma gondii DNA, providing molecular evidence supporting the diagnosis. The patient denied cat ownership or close feline exposure but reported occasional consumption of raw salmon. Treatment consisted of oral trimethoprim-sulfamethoxazole combined with methylprednisolone and two intravitreal injections of clindamycin plus dexamethasone. Significant regression of the retinal lesion was observed after treatment. This case highlights the diagnostic value of intraocular fluid mNGS in ocular toxoplasmosis and emphasizes the importance of considering ocular toxoplasmosis in patients presenting with posterior uveitis involving the macula, even in the absence of traditional epidemiological risk factors.