An extended phenotype of RP1L1 maculopathy - case report

To report the ophthalmological findings of a new phenotypical variant of RP1L1 maculopathy in an Indian patient with a homozygous variant in the RP1L1 gene.

A 39-year-old male presented with complaints of disturbance in the central field of vision in both eyes (BE) for a duration of 6 months. He underwent ophthalmic examinations and diagnostic imaging. A complete retinal degeneration panel consisting of 228 genes was evaluated for pathologic variations using next-generation sequencing (NGS), which showed a variant in the RP1L1 gene.

On fundus examination, he was found to have ill-defined foveal mottling in BE. Spectral domain optical coherence tomography (SD-OCT) showed sub-foveal hyper-reflective deposits and outer retinal layer disruption. A provisional diagnosis of the atypical variant of adult-onset foveomacular vitelliform dystrophy (AOFVD) was made on the basis of clinical, OCT, Fundus autofluorescence (FAF) and electrophysiological features. Genetic assessment of the proband revealed the presence of a homozygous base pair deletion in exon 4 of RP1L1 gene (chr8:g.10468194_10468195del), which results in frameshift and premature truncation of the protein 24 amino acids downstream to codon 1138 (p.Lys1138SerfsTer24). This variant was confirmed in the proband's parents by Sanger sequencing. The diagnosis was revised to RP1L1 maculopathy, as the RP1L1 gene variant is most commonly associated with this entity.

This report presents the multimodal imaging of a previously unreported phenotype of RP1L1 maculopathy associated with a genetic variant of RP1L1 gene, thereby expanding the spectrum associated with RP1L1 maculopathy.