Clinical and genetic findings in Italian patients with sector retinitis pigmentosa

Purpose: To describe clinical and genetic features in a series of Italian patients with sector retinitis pigmentosa (sector RP). Methods: Fifteen patients with sector RP were selected from the database of Hereditary Retinal Degenerations Referring Center of Careggi Hospital (Florence, Italy). Eleven patients from five independent pedigrees underwent genetic analysis with next-generation sequencing (NGS) confirmed with Sanger sequencing. The diagnosis of sector RP was based on the detection of topographically limited retinal abnormalities consistent with corresponding sectorial visual field defects. Best-corrected visual acuity (BCVA), fundus color pictures as well as fundus autofluorescence (FAF), spectral domain-optical coherence tomography (SD-OCT), full-field electroretinography (ERG), and 30–2 Humphrey visual field (VF) data were retrospectively collected and analyzed. Results: For the 30 eyes, the mean BCVA was 0.05 ± 0.13 logMAR, and the mean refractive error was −0.52 ± 1.89 D. The inferior retina was the most affected sector (86.7%), and the VF defect corresponded to the affected sector. FAF showed a demarcation line of increased autofluorescence between the healthy and affected retina, corresponding on SD-OCT to an interruption of the ellipsoid zone (EZ) band in the diseased retina. Dark-adapted ERG amplitudes were decreased in comparison to normative values. In five unrelated families, the sector RP phenotype was associated with sequence variants in the RHO gene. The same mutation c.568G>A p.(Asp190Asn) was found in nine patients of four families. Conclusions: Typical sector RP is a mild form of RP characterized by preserved visual acuity with limited retinal involvement and, generally, a more favorable prognosis than other forms of RP.