Cone-Rod Dystrophy PCARE-Associated Retinopathy

Background and Clinical Significance: Biallelic pathogenic variants in the PCARE gene (photoreceptor cilium actin regulator), also known as C2orf71 (chromosome 2 open reading frame 71), are typically associated with retinitis pigmentosa type 54 (RP54) and, less frequently, with cone-rod dystrophy (CORD23). Case Presentation: A 52-year-old man presented with an eight-year history of progressive visual loss, without photophobia or nyctalopia. He underwent a comprehensive ophthalmological evaluation, including multimodal retinal imaging, automated perimetry, and full electrophysiological testing, in accordance with International Society for Clinical Electrophysiology of Vision (ISCEV)'s standards. Genetic testing was performed using next-generation sequencing (NGS) with an inherited retinal dystrophy gene panel, and findings were confirmed by Sanger sequencing. Clinical examination revealed bilateral macular atrophy with minimal foveal sparing and a central scotoma. Optical coherence tomography (OCT) showed disruption of the outer retinal layers and retinal pigment epithelium (RPE) abnormalities. Fundus autofluorescence (FAF) demonstrated central hypoautofluorescence surrounded by a hyperautofluorescent ring. Electrophysiological testing revealed severely reduced rod- and cone- mediated responses on full-field electroretinography (ERG), absent pattern ERG responses, and markedly reduced multifocal ERG responses, indicating widespread retinal dysfunction with significant macular involvement. Genetic analysis identified a homozygous pathogenic nonsense variant in PCARE [c.3289C>T; p.(Gln1097*)], confirming the diagnosis of an autosomal recessive inherited retinal dystrophy. Conclusions: Biallelic PCARE variants can cause late-onset severe retinal dystrophy, with predominant macular involvement and cone-rod dysfunction. Given its phenotypic overlap with other inherited retinal diseases, accurate diagnosis requires the integration of multimodal retinal imaging, electrophysiological testing, and comprehensive genetic analysis.