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A54-year-old man presented with a diffuse macular necrotizing retinitis in his right eye (Fig. 1A). He was put on treatment on high-dose oral corticosteroids without clinical improvement. His medical history was post-transfusional hepatitis C. At presentation, his visual acuity (VA) was counting fingers in the right eye and 20/20 in the left eye. Fluorescein angiography demonstrated late hypofluorescence in the area of retinitis (Fig. 1B). Routine blood tests, serology for veneral disease and a Mantoux test were within normal limits. The toxoplasma IgG titre was positive at 238 IU/ml (normal,<6 IU/ml);but IgM levels were not elevated. A brain computed tomography scan was normal. Because of no clinical improvement, a diagnostic pars plana vitrectomy was performed. An undiluted vitreous aspirate was obtained at the start of the procedure, and a subretinal aspirate from the area of the retinitis was taken with a 33G cannula. Vitreous polymerase chain reaction (PCR) was negative for herpes virus and toxoplasma, and a vitreous biopsy showed only chronic inflammatory cells. Cytological examination of the subretinal aspirate recovered during the operation revealed Toxoplasma organisms (Fig. 1C). Oral treatment was begun with sulphadiazine (4 g load followed by 1 g four times a day), pyrimethamine (100 mg load followed by 25 mg twice a day).Prednisone added to the regimen 2 days later after antitoxoplasmic therapy was begun. One month after, his VA in the right eye was 20/200 (Fig. 1D) Twelve months after surgery, fundoscopy revealed an atrophic area in the macular region.

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Figure 1.  (A) Fundus photograph in the right eye showing a macular necrotizing retinitis and vitreous cells. (B) Late-phase fluorescein angiography in the right eye showing hypofluorescence in the area of retinitis. (C) Cytopathological examination of the subretinal aspirate recovered during the operation revealed Toxoplasma cyst in a cytospin preparation (arrow). (D) Fundus photograph in the right eye 1 month after surgery showing scarring of macular retinitis.

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Toxoplasma gondii is a common cause of posterior segment inflammation. The diagnosis of toxoplasma retinochoroiditis can usually be confidently made on the basis of clinical signs, with the results of serologic studies assisting in confirmation of the diagnosis. Nevertheless, toxoplasmic chorioretinitis can present without a typical small to moderate focus of active chorioretinitis adjacent to a healed chorioretinal scar and can be difficult to diagnose ophthalmoscopically. Extensive toxoplasmic chorioretinitis has been reported previously and is considered rare (Fardeau et al.2002). Differential diagnosis of such lesions includes fungal infection, viral retinitis and intraocular lymphoma. Use of invasive diagnostic procedures in patients with sight-threatening chorioretinitis that cannot be satisfactorily diagnosed by ophthalmoscopy, or in patients without response to a chosen empiric therapy, may result in better visual and anatomic outcomes (Johnston et al. 2004). PCR-based analyses of vitreous or aqueous specimens have extended the range of conditions that can be reliably diagnosed without resorting to tissue biopsy of either the retina or choroid (Montoya et al. 1999).As in our patient, however, the sensitivity of PCR-based assays of ocular fluids to detect Toxoplasma antigens may not be high enough to confirm the diagnosis. Retinal and choroidal biopsies are only taken after appropriate extensive systemic and less invasive ocular investigations have failed to confirm a diagnosis. Necrotizing retinitis caused by Toxoplasma gondii may sometimes be diagnosed cytologically from vitreous specimens (Greven & Teot1994; Belfort et al. 2008).Cytology and immunostaining of vitreous samples were taken in our case to identify Toxoplasma gondii but were negative. The diagnosis was finally made on cytopathologic examination of the subretinal aspirate, which showed the typical encysted organisms.

Although vitreous and subretinal aspiration is unlikely to become a primary investigation, it should perhaps be considered at an earlier stage, because it might allow earlier initiation of specific therapy that might prevent severe visual loss. Our case confirms the value of subretinal aspiration in the diagnosis of atypical cases of ocular toxoplasmosis.

References

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  2. References
  • Belfort RN, Rasmussen S, Kherani A, Lodha N, Williams G, Fernandes BF & Burnier MN Jr (2008): Bilateral progressive necrotizing retinochoroiditis in an immunocompromised patient: histopathological diagnosis. Acta Ophthalmol [Epub ahead of print].
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  • Greven CM & Teot LA (1994): Cytologic identification of Toxoplasma gondii from vitreous fluid. Arch Ophthalmol 112: 10861088.
  • Johnston RL, Tufail A, Lightman S, Luthert PJ, Pavesio CE, Cooling RJ & Charteris D (2004): Retinal and choroidal biopsies are helpful in unclear uveitis of suspected infectious or malignant origin. Ophthalmology 111: 522528.
  • Montoya JG, Parmley S, Liesenfeld O, Jaffe GJ & Remington JS (1999): Use of the polymerase chain reaction for diagnosis of ocular toxoplasmosis. Ophthalmology 106: 15541563.