A Case of Retinopathy–Sensory Neuropathy Syndrome With a Novel Compound Heterozygous FLVCR1 Variant

Background and Aims: Retinopathy–sensory neuropathy syndrome (RETSNS), also known as posterior column ataxia with retinitis pigmentosa (PCARP), is a rare neurodegenerative disorder that is caused by biallelic pathogenic variants in FLVCR1. Here, we report a case of a Japanese patient with RETSNS.<br> Methods: Clinical, neuroradiological, and electrophysiological findings were documented. Whole-genome sequencing was performed. Subcloning was carried out to confirm compound heterozygosity. A functional assay was performed to assess the pathogenicity of the variants.<br> Results: The patient showed retinitis pigmentosa and sensory ataxia. Over the course of the disease, autonomic dysfunction has become increasingly evident. Despite consanguinity in the family, whole-genome sequencing identified two heterozygous variants in FLVCR1 (c.369T>G, p.Phe123Leu and c.733A>G, p.Asn245Asp). Cloning of the PCR product followed by Sanger sequencing indicated compound heterozygosity of the variants. Immunocytochemistry of HEK293FT cells transfected with plasmids containing wild-type or variant FLVCR1 cDNA demonstrated altered subcellular localization of the variant FLVCR1 proteins, characterized by reduced membrane localization.<br> Interpretation: We report a novel variant in FLVCR1 causing RETSNS. The functional assay supports the pathogenicity of the variants.