Bilateral progressive necrotizing retinochoroiditis in an immunocompromised patient: histopathological diagnosis

A 66-year-old man with a 10-year history of splenic B-cell lymphoma and Pneumocystis carinii pneumonia presented with floaters and photopsia in the right eye. The fundus exam showed a few retinal haemorrhages with vitritis (Fig. 1A and 1B). The diagnosis of cytomegalovirus (CMV) retinitis was made. The patient was treated with topical steroids, atropine, brimonidine, repeated injections of intravitreal gancyclovir and a short course of oral valganciclovir 900 mg twice daily. The patient’s right eye stabilized and vision improved to 20/25. After 1 month, he presented with similar lesions on the left eye accompanied by anterior chamber haemorrhage (Fig. 1C). The left eye received treatment similar to the right eye. Despite treatment, the disease in his left eye progressed and vision deteriorated to counting fingers. A diagnostic vitrectomy was performed in his left eye and, despite negative cultures and polymerase chain reaction (PCR) for viruses and lymphoma, the patient continued treatment for CMV retinitis based on clinical suspicion and apparent response to treatment in his right eye. He then received a higher dosage of intravitreal ganclovir (1 mg). However, there was no improvement and even perception of light was lost in his left eye. A diagnostic enucleation was performed and the specimen showed large areas or retinal necrosis and extensive inflammatory infiltrate within the choroid (Fig. 1D). A few retinal toxoplasma cysts could be seen (Fig. 1E), confirmed by immunohistochemistry (Fig. 1F). Also, eosinophilic deposits under the retinal pigment epithelium (RPE) corresponding to necrosis of Bruch’s membrane were present (Fig. 1E). Based on the histopathological findings, the diagnosis of ocular toxoplasmosis was made. Unfortunately, because of complications of his systemic disease, the patient died soon after the diagnosis was made. (A and B) Funduscopic examination of the right eye with extensive necrotizing retinochoroiditis associated with vitreous inflammatory reaction and absence of ophthalmoscopically visible chorioretinal scarring. (C) Slit-lamp photography of the left eye showing anterior chamber haemorrhage. (D) Area of extensive retinal necrosis and choroidal granulomatous inflammation [haematoxylin and eosin (H&E), × 100]. (E) High magnification of a necrotic retina with a large cyst (arrow) and eosinophilic deposit under the retinal pigment epithelium (arrowhead) (H&E, × 400). (F) Immunohistochemical staining labels in red showing a toxoplasma cyst within the retina (× 400). Ocular toxoplasmosis is caused by the protozoa Toxoplasma gondii, and can be acquired congenitally or by ingesting uncooked infected meat or contaminated vegetables and water (Silveira et al. 1988). In immunocompetent patients it usually presents as a unilateral granulomatous uveitis with retinochoroiditis and moderated to severe vitritis. Recurrences are usually observed as an active retinal lesion adjacent or near to a retinochoroidal scar. In immunocompromised patients, the presentation of toxoplasmosis can be atypical. Multiple lesions, bilaterality, retinal vasculitis, retinal vascular occlusions, retinal detachments, pigmentary retinopathy mimicking retinitis pigmentosa, neuroretinitis, optic neuropathy (Kallenbach & Frederiksen 2008) and scleritis are some of the unusual presentations (Smith & Cunningham 2002). CMV retinopathy is an opportunistic infection that usually affects immunocompromised patients. It typically presents with retinal necrosis accompanied by haemorrhage and little inflammatory response. Ocular toxoplasmosis in immunodeficient patients might present in a very similar clinical picture. Although for most patients the distinction can be made on clinical grounds, histopathology is occasionally required to distinguish between the two aetiologies. Pathological diagnosis of ocular toxoplasmosis can be obtained by chorioretinal biopsies or diagnostic enucleation. The toxoplasma cysts are identified with haematoxylin and eosin (H&E), immunohistochemistry (Rao & Font 1977) or by PCR (Brezin et al. 1990). In some cases, chorioretinal biopsies yield sufficient material to avoid enucleation. Additionally, vitreous and humour aqueous samples can be analysed using PCR to identify parasite DNA (Burg et al. 1989); serum levels of chemokines (CXCL8) can also be used, particularly during follow-up (Goncalves et al. 2007). For the diagnosis of CMV retinitis, infected giant cells are seen easily in most cases. Whenever the hallmarks of each condition are not seen readily, other pathological findings are useful to make such a distinction. Ocular toxoplasmosis often presents extensive granulomatous inflammatory infiltration of the choroid and areas of necrosis of Bruch’s membrane – neither of which are seen in CMV retinitis. The latter is of particular interest because it may partially explain why immunocompetent patients present choroidal inflammation even though the parasite is invariably confined to the retina. The breaks in Bruch’s membrane would permit the contact of the choroid with infectious antigen that secondarily would cause an inflammatory response. Also, these focal areas of necrosis are an important clue to establish the correct diagnosis of toxoplasmosis – especially in immunocompromised patients, when the inflammatory infiltrate may be minimal or absent.

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