Novel Heterozygous Variant in <i>RP1L1</i> Gene With Retinitis Pigmentosa Phenotype: A Case Report

This report presents a novel heterozygous mutation in <i>RP1L1</i> resulting in an asymptomatic retinitis pigmentosa (RP) phenotype. A 37-year-old woman with no visual complaints and 20/20 best-corrected visual acuity was incidentally found to have bilateral retinal pigment mottling and diffuse speckled hypoautofluorescence in both eyes. Ultra-high-resolution optical coherence tomography (OCT) showed intact outer retinal structures. Visual field testing only showed nonspecific defects, in the context of multiple fixation losses and poor reliability. Genetic testing identified a novel mutation in the <i>RP1L1</i> gene, and three other mutations of unknown significance in the RP GTPase regulator interaction protein 1 gene (<i>RPGRIP1</i>), ATP-binding cassette transporter 4 gene (<i>ABCA4</i>), and glutamate metabotropic receptor 6 gene (<i>GRM6</i>). While <i>RP1L1</i> is typically associated with autosomal recessive inheritance and is polymorphic among those screened for inherited retinal disease, it is hypothesized that the combination of multiple mutations may contribute to the patient's phenotypic manifestations, despite her heterozygous status for <i>RP1L1</i>.