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The 13q deletion syndrome is an uncommon chromosomal disorder affecting the long arm of chromosome 13 which is deleted to a variable degree.1 This syndrome is phenotypically characterised by mental retardation, structural malformations, facial dysmorphism, and a predisposition to develop retinoblastoma.1 This intraocular tumour is diagnosed in approximately 80% of cases with this syndrome.2 Moreover, the incidence of bilateral retinoblastoma is much higher in individuals with this syndrome.3,4 The retinoblastoma susceptibility gene (RB-1), which encodes for the nuclear phosphoprotein of 105 kDa, is located in band 13q14.5 The involvement of the q14 band on the long arm of chromosome 13 places patients with this syndrome at significant risk for developing retinoblastoma.6 In addition, children with 13q deletion syndrome also show optic nerve hypoplasia and retinal dysplasia.7 In this case, we report additional findings of pars plana ciliaris epithelial proliferation in 13q deletion syndrome.
A 5 month old Hispanic female infant with a karyotype 46,XX, del (13) (q14.1q21.3) was referred to us for the evaluation of retinoblastoma. She had dysmorphic features, such as craniosynostosis. There was no family history of ocular or systemic disease. While under anaesthesia, the patient’s right eye was examined, revealing a mass that occupied a large area of the inferior nasal portion of the retina, and extending into the vitreous cavity (Fig 1). It obscured the optic nerve head and was associated with retinal detachment. There were also fine vitreous seedings. Ultrasonography disclosed a retinal tumour with intralesional calcific foci. The preoperative diagnosis was retinoblastoma with vitreous seedings, and she underwent enucleation of the globe. The left eye was unremarkable.
Macroscopic examination revealed a greyish-white tumour arising from the retina that exhibited calcific foci and was extended into the vitreous cavity. Histological examination of the tumour indicated a well differentiated retinoblastoma that displayed both Flexner-Wintersteiner and Homer-Wright rosettes (Fig 1). There was no tumour invasion of the uvea or the post laminar optic nerve. In addition, the globe showed multilayered plaquoid non-pigmented ciliary epithelial proliferation at the pars plana ciliaris (Fig 2) and optic nerve hypoplasia. The epithelial proliferation revealed benign histological features, unlike the malignant neoplastic proliferation of the retina. At the pars plana ciliaris, the pigment epithelium showed focal proliferation.
The extent of the deletions affecting the long arm of chromosome 13 may result in various developmental anomalies that constitute 13q syndrome.2,8 Proliferation of the pars plana ciliaris non-pigmented ciliary epithelium, as noted in the present case, and its association with retinoblastoma suggests that the RB-1 gene, or a gene close to the RB-1 locus may have a role in the proliferation of the other neuroepithelial structures of the eye, including the pars plana ciliary epithelium.
In embryological terms, the non-pigmented ciliary epithelium is derived from the inner layer of the optic cup which also gives rise to the neural retina.9 Proliferation of the pars plana ciliary epithelium in an eye that harbours retinoblastoma suggests that the RB-1 gene may play a part in such epithelial proliferation. However, this epithelial proliferation has not been previously reported in eyes with retinoblastoma. Although the cause of proliferation of the ciliary epithelium is not clear, this case suggests that the non-pigmented ciliary epithelial proliferation at the pars plana ciliaris in an eye that harbours retinoblastoma may be related to 13q deletion syndrome. Such findings may be unique to this syndrome, but previous reports about it have not mentioned them. The lack of previously reported cases with findings of pars plana epithelial proliferation suggests that this syndrome may have variable phenotypic expression.
This work was supported in part by NEI core grant Ey03040 and by an unrestricted grant from Research to Prevent Blindness Inc, New York, USA. The clinical illustration is provided by Dr Linn A Murphree.