Unusual Paraneoplastic Cause of Vision Loss: Combined Paraneoplastic Cone Dystrophy and Optic Neuropathy

Comment. Toxoplasmosis is believed to be the most common cause of posterior uveitis. Scleritis in association with toxoplasmic retinochoroiditis is an uncommon entity. Accordingly, in a review of 243 patients with scleritis, no patient was reported to have toxoplasmic infection as a cause; furthermore, 37% had a systemic rheumatologic disorder, only 7% had an infection, and 44% had an associated medical disorder. Herpes zoster virus was the most commonly reported infectious cause and rheumatoid arthritis was the most common rheumatic disease. In cases of toxoplasmic scleritis, the inflammatory response is believed to extend from the active retinochoroiditis to involve the overlying sclera. Accordingly, pathologic specimens from eyes that were enucleated secondary to severe toxoplasmic scleritis displayed granulomatous inflammation of the retina, uvea, and episclera with associated retinal thickening. In many cases, the entire sclera extending outward from the retinitis was inflamed; however, in some cases, a region of uninflamed sclera separated the active scleritis from the underlying retinitis. Isolated toxoplasmic retinochoroiditis can rapidly spread and lead to severe permanent vision loss when treated with steroids alone. In our patient with scleritis, a dilated fundus examination revealed an area of typical toxoplasmic retinochoroiditis, allowing for prompt diagnosis and treatment with appropriate antibiotic therapy. The patient improved and maintained excellent visual acuity. This patient’s course underscores the importance of a complete examination in cases of scleritis, including a dilated fundus examination, to rule out an infectious retinochoroiditis in association with the scleritis.