Neuroglia Cell-Originated Vitreous Cyst in a Retinitis Pigmentosa Patient

A 47-year-old female presented with a complaint of a dark shadow floating in front of her right eye. She was diagnosed with retinitis pigmentosa in both eyes 15 years ago in Southwest Hospital. On examination, her presenting visual acuity was 20/400 in both eyes. Visual acuity did not improve even with pinhole and best refractive correction. On slitlamp examination, anterior segment of both eyes was normal. Intraocular pressure of both eyes was within reference limit. On posterior segment examination, fundus evaluation of both eyes revealed typical bone-spicule pigment, and a free-floating cyst of about 6 mm in diameter was seen in the vitreous cavity of the right eye (Fig. 1A). The patient expressed a strong desire for surgery to relieve the dark shadow in her right eye.FIGURE 1: A, Funduscopy showed a free-floating cyst in the vitreous cavity and bone-spicule pigment in the retina. The cyst was gray-white and about 6 mm in diameter. B, Hematoxylin-eosin staining and immunohistochemical staining (GFAP, syn, and S100) of the capsule wall. GFAP indicates glial fibrillary acidic protein; S100, calcium binding protein; syn, synuclein.The cyst was removed by 25-G pars plana vitrectomy (Supplementary Digital Content Video, https://links.lww.com/APJO/A195). Immunohistochemical staining of the capsule wall showed glial fibrillary acidic protein (GFAP), S100 (calcium binding protein), and synuclein (syn) positive (Fig. 1B). GFAP and S100 are markers of neuroglia cells, which are expressed in astrocytes and Muller glia cells of the retina. Syn can also be expressed in activated neuroglia cells. While our staining also showed melanocyte markers (HMB45, MelanA), epithelial cell marker (cytokeratin), macrophage marker (CD68), and lymphocyte marker (CD45) were all negative. These suggested the vitreous cyst originated from the neuroglia cell. Vitreous cysts are rare clinical findings, which can be congenital or acquired. Congenital ones have been reported to be associated with the residual hyaloid vascular system. Acquired ones are usually associated with ocular trauma, uveitis, intraocular infection, retinitis pigmentosa, and retinal detachment.1 Most vitreous cysts can be observed without any treatment. Laser disruption or vitrectomy may be performed when the patient has obvious symptoms and a strong desire for therapy. In our case, the cyst occurred in retinitis pigmentosa and originated from the neuroglia cell. The patient no longer complained about the floater after the operation.