# Clinical and Genetic Characteristics of Senior-Loken Syndrome Patients in Korea

## TL;DR

This study examines the clinical and genetic features of Senior-Loken syndrome in Korean patients, revealing varied eye and kidney symptoms based on specific gene mutations.

## Contribution

The study provides new insights into genotype-phenotype correlations in Korean Senior-Loken syndrome patients, highlighting variable clinical manifestations.

## Key findings

- NPHP1 mutations were most common and associated with preserved central vision despite kidney issues.
- IQCB1 mutations often caused severe retinal degeneration, including Leber congenital amaurosis.
- Younger patients showed better visual preservation regardless of genetic mutation.

## Abstract

Background/Objectives: Senior-Loken syndrome (SLS) is a rare autosomal recessive renal–retinal disease caused by mutations in 10 genes. This study aimed to review the ophthalmic findings, renal function, and genotypes of Korean SLS cases. Methods: We retrospectively reviewed 17 genetically confirmed SLS patients in Korea, including 9 newly identified cases and 8 previously reported. Comprehensive ophthalmologic evaluations and renal assessments were conducted. Genetic testing was performed using whole-genome sequencing (WGS), whole-exome sequencing (WES), or Sanger sequencing. Results: Among the 17 patients, patients with NPHP1 mutations were most common (35.3%), followed by those with NPHP4 (29.4%), IQCB1 (NPHP5, 29.4%), and SDCCAG8 (NPHP10, 5.9%) mutations. Patients with NPHP1 mutations showed retinitis pigmentosa (RP) sine pigmento and preserved central vision independent of renal deterioration. Patients with NPHP4 mutations showed early renal dysfunction. Two patients aged under 20 maintained relatively good visual function, but older individuals progressed to severe retinopathy. Patients with IQCB1 mutations were generally prone to early and severe retinal degeneration, typically manifesting as Leber congenital amaurosis (LCA) (three patients), while two patients exhibited milder RP sine pigmento with preserved central vision. Notably, two out of five (40.0%) maintained normal renal function at the time of diagnosis, and both had large deletions in IQCB1. The patient with SDCCAG8 mutation exhibited both end-stage renal disease and congenital blindness due to LCA. Wide-field fundus autofluorescence (AF) revealed perifoveal and peripapillary hypoAF with a perifoveal hyperAF in younger patients across genotypes. Patients under 20 years old showed relatively preserved central vision, regardless of the underlying genetic mutation. Conclusions: The clinical manifestation of renal and ocular impairment demonstrated heterogeneity among Korean SLS patients according to causative genes, and the severity of renal dysfunction and visual decline was not correlated. Therefore, simultaneous comprehensive evaluations of both renal and ocular function should be performed at the initial diagnosis to guide timely intervention and optimize long-term outcomes.