Profound Visual Impairment With Limited Retinal Structural Abnormalities: A Case of Suspected Photoreceptor Cilium Actin Regulator (PCARE)-Associated Retinopathy

Photoreceptor cilium actin regulator (PCARE)-associated retinopathy is a rare autosomal recessive inherited retinal disorder caused by pathogenic variants in the PCARE (formerly C2orf71) gene and encompasses a wide range of clinical phenotypes.Variability in disease severity and retinal findings, together with the complexity of genetic testing, can make diagnosis challenging.We report a 73-year-old Hispanic female patient referred for genetic evaluation of profound bilateral visual impairment, with a family history of blindness.The patient's best-corrected visual acuity was no light perception in the right eye (OD) and 20/400 in the left eye (OS), with red-green and blue-yellow color vision deficiencies.Fundus examination demonstrated mild retinal vascular attenuation without prominent peripheral pigmentary changes.Fundus autofluorescence of the OS revealed decreased central macular autofluorescence with surrounding alterations.Optical coherence tomography demonstrated decreased retinal thickness and volume with absence of the normal foveal pit in the OD.In contrast, retinal thickness and volume remained within normal limits in the OS.Central subfield thickness (CST) was 229 µm in the OD and 236 µm in the OS, with macular cube volumes of 8.6 mm³ and 9.3 mm³, respectively.Humphrey 24-2 visual field testing of the OS demonstrated profound diffuse visual field loss, with a visual field index of 0% and a reported mean deviation of -31.63 dB.However, the instrument indicated that the mean deviation threshold had been exceeded.Next-generation sequencing identified two heterozygous PCARE variants of uncertain significance, c.1453G>A (p.Glu485Lys) and c.739_740delinsAA (p.Val247Asn), with unknown phase.The marked discrepancy between visual dysfunction and retinal structural findings, together with inconclusive molecular results, presents a diagnostic challenge.This case highlights the importance of careful genotype-phenotype correlation and consideration of additional genetic evaluation in patients with suspected inherited retinal dystrophies.