Unique retinal phenotype may support pathogenicity of FSCN2 in inherited retinal degenerations: a case report and review of the literature

Purpose To describe a peculiar retinal phenotype associated with a novel variant in FSCN2.Methods The patient underwent a comprehensive ophthalmic exam, imaging with spectral domain optical coherence tomography (SD-OCT) and fundus autofluorescence and vision measured with kinetic fields and full-field electroretinography (ffERG).Results A 67-year-old man presented with a history of blurred vision for about 20 years. Visual acuities were 20/150 in each eye. Goldmann kinetic visual fields were generally full in extent to a V-4e target, but smaller I-4e stimulus fields were limited to a remnant island of vision in the pericentral infero-nasal field that excluded fixation. There was a ceco-central oval area of pigmentary changes bilaterally that was densely hypo-autofluorescent on short-wavelength and near-infrared excitation. On SD-OCT, there was severe photoreceptor outer nuclear layer loss with steep transitions into normal‑appearing retina. ffERGs were reduced in amplitude for cone-mediated responses; rod-mediated ffERGs were within normal limits. Genetic testing revealed a missense mutation in the FSCN2 gene (c.917A > G, p.Tyr306Cys).Conclusions This novel variant in FSCN2 shows a cone-rod dystrophy phenotype and a stereotypical pattern of ceco-central abnormalities reminiscent of earlier reports in patients with FSCN2-associated retinopathies, supportive of the role of FSCN2 in inherited retinal degenerations with a central predilection and of the potential pathogenicity of this FSCN2 variant.