Retinitis Pigmentosa Sine Pigmento in a Carrier of Usher Syndrome.

We report a carrier of Usher syndrome type I with retinitis pigmentosa sine pigmento. A 71-year-old male was referred for further evaluation of severe, progressive, painless vision loss in both eyes over the course of four years. He had bilateral sensorineural hearing loss. Upon a comprehensive examination, his best-corrected visual acuity was 20/100 in the right eye and 20/40 in the left eye. He had an unremarkable anterior segment examination and normal intraocular pressures in both eyes. Upon fundus examination, the patient had pale discs, optic disc cupping, and multiple scattered drusen in the macula and at the midperiphery of both eyes. Optical coherence tomography showed retinal nerve fiber layer thinning in all quadrants. The visual field was severely constricted in both eyes. A comprehensive workup for infectious and inflammatory causes, as well as a brain MRI, was unremarkable. Sequencing analysis showed that he carried a heterozygous pathogenic mutation, USH1C c.672C>A (p.Cys224*) variant. Usher syndrome is a rare genetic disease characterized by hearing loss and retinitis pigmentosa. Our case suggests that patients and carriers of Usher syndrome may have a phenotype compatible with retinitis pigmentosa sine pigmento.

Pseudodominant Inheritance of Retinitis Pigmentosa Due to Mutations in the Phosphodiesterase 6B Gene: A Case Report.

Mutations in the phosphodiesterase 6B (PDE6B) gene are a rare cause of autosomal recessive retinitis pigmentosa (arRP). We report on a non-consanguineous family with a pseudodominant inheritance of RP due to PDE6B mutations. We conducted a chart review of four members of a Puerto Rican family who underwent a comprehensive ophthalmic evaluation by at least one of the authors. The mutational screening was done using a genotyping microarray provided by Invitae Corporation, using next-generation sequencing (NGS) technology. Genomic DNA obtained from saliva samples is enriched for targeted regions using a hybridization-based protocol and sequenced using Illumina technology. A descriptive analysis was done. Patient 1A had a normal ophthalmic examination and a heterozygous pathogenic variant in the PDE6B gene c.1540del PLeu514Trpfs*61. Patients 1B, 2A, and 2B had mid-peripheral retinitis pigmentosa, concentric visual field ring scotomata in both eyes (OU), extinguished electroretinogram (ERG), and homozygous pathogenic variants in the PDE6B gene c.1540del PLeu514Trpfs*61. Even though mutations in the PDE6B gene usually lead to arRP, they may be inherited in a pseudodominant pattern in geographically isolated populations. Genotyping studies in patients with RP are warranted to classify inheritance mode correctly.