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Several ocular conditions can clinically simulate retinoblastoma by producing either a leucocoria or an ophthalmoscopically visible intraocular mass. In a large series of patients referred with the clinical diagnosis of retinoblastoma, 42% were found to have benign lesions that simulated retinoblastoma.1 The three lesions that most often clinically mimic retinoblastoma are persistent hyperplastic primary vitreous, Coats’ disease, and ocular toxocariasis.1 Herein we report a case of intraocular cysticercosis in a 5-year-old child presenting with leucocoria, and simulating retinoblastoma.

Case report

A systemically healthy 5-year-old male child was referred with a history of pain and redness in the left eye (LE) of 20 days duration. He had been initially diagnosed and treated as a case of conjunctivitis, and later suspected to have endophthalmitis. On examination, the LE had no light perception. There was mild lid oedema, conjunctival congestion, and mild corneal oedema. The anterior chamber was deep with 2+flare and a trace of cells. The lens was clear and there was a white pupillary reflex. The intraocular pressure by Perkins applanation tonometer was unrecordably low. Indirect ophthalmoscopy revealed retinal detachment and a large (20×18×16 mm) intravitreal vascularized yellowish mass. A- and B-scan ultrasonography demonstrated an intraocular mass occupying most of the vitreous cavity and choroidal thickening (Figure 1). The mass showed several areas of high internal reflectivity and orbital shadowing (Figure 1), suggestive of intraocular calcification. As a result of inflammation associated with a calcified intraocular mass in a child, a necrotic retinoblastoma and a toxocara granuloma were considered in the differential diagnosis. The sightless and symptomatic eye was enucleated and sent for histopathologic examination.

Figure 1
figure 1

Ultrasonography B-scan (top) demonstrates an echodense intravitreal-space-occupying lesion with varying echogenecity, almost filling the entire vitreous cavity. Note the orbital shadowing. The corresponding vector A-scan (bottom) shows high internal reflectivity.

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On gross examination, the eye was normal in size. The cut section revealed a large solid intravitreal mass with an eccentrically situated cystic cavity. The microscopic examination showed total retinal detachment, solid vitreoretinal proliferation, diffuse infiltration by lymphocytes, plasma cells, eosinophils, and an eccentric abscess cavity (Figure 2). A cyst with a wall lined by a wavy cuticle and a smooth muscle layer was noted within the abscess cavity. Giant cell reaction was noted within the surrounding cyst wall (Figure 2, inset). The choroid was thickened with oedema, congested vessels, and mononuclear cell infiltration. Although definite scolex and hooklets were not identified, the characteristics of the cyst wall were diagnostic of cysticercosis.

Figure 2
figure 2

The whole mount section of the eyeball (left) shows a solid vitreoretinal mass (*), occupying the entire vitreous cavity. Note the abscess with a cyst (arrow) at the periphery of the mass (haematoxylin and eosin, ×5). The microscopic examination of the section of the eyeball (right) shows degenerating wall of the cysticercus within the cavity, with multinucleated giant cells (inset) in the wall of abscess cavity (haematoxylin and eosin, ×250).

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Comment

Cysticercosis, an infestation by the larval form of the cestode Taenia solium, is a common ocular parasitosis.2 Once considered as an endemic disease in developing countries, there has been a gradual change in the socio-demographic trends of ocular cysticercosis.3 The disease is now being diagnosed with increasing frequency the world over, and is no longer a medical curiosity.2,3 On review of all documented cases of ocular cysticercosis, it was found that 35% of the cysts were reported in the subretinal space, and 22% in the vitreous.2 Intraocular cysticercosis usually presents with reduction of vision, and signs of ocular inflammation.2,3,4 It is believed that the larva reaches the subretinal space through posterior ciliary arteries.2,3,4,5 As the cyst develops, it may cause exudative retinal detachment.4,5 Perforation of retina results in a free-floating intravitreous cyst.2 Most often, the characteristic intraocular cyst can be visualized by an indirect ophthalmoscope, or detected by ultrasound B-scan in the presence of media haze.2 Histologically, cysticercus consists of a single invaginated protoscolex within the cavity of fluid-filled cyst. The protoscolex has suckers and hooklets, while the three-layered cyst wall consists of a cuticle, a smooth muscle layer, and tegumental cells with scattered calcareous corpuscles.

As long as the cyst remains viable, it evokes a little or no inflammatory response. Once the cyst starts degenerating, an antigen, which may be a metabolic by-product or toxin, leaks from the cyst and induces an inflammatory reaction,2 manifesting as vitritis, uveitis, and sometimes endophthalmitis.2,3,4,5 An unusual feature of our patient was that he presented as leucocoria with ocular inflammatory signs, and an ultrasonographic appearance of calcification. This clinical presentation in a child strongly points towards the diagnosis of necrotic rentinoblastoma.1,6 The density of the inflammatory reaction within the vitreoretinal mass surrounding the cyst probably hindered the detection of the cyst by ultrasound B-scan and simulated intraocular calcification. The degenerating parasite possibly evoked the surrounding granulomatous reaction and the vitreoretinal proliferation.

Although rare, intraocular cysticercosus could present as leucocoria and pose a diagnostic problem in children. It should be considered in the differential diagnosis of leucocoria presenting with ocular inflammation, especially in endemic areas.