Why this study matters for Usher syndrome

Usher syndrome is an inherited condition in which retinitis pigmentosa (RP)—a progressive retinal disease that affects vision—occurs alongside hearing loss. For individuals and families, receiving a precise molecular diagnosis can be an important step in understanding the cause of disease, connecting clinical findings to a specific gene, and preparing for a rapidly evolving research landscape.

A 2026 study in Investigative Ophthalmology & Visual Science examined the genetic landscape of inherited retinal dystrophies (IRDs) in a white Polish cohort using whole-exome sequencing (WES). The study included 203 participants, among them 21 people with Usher syndrome. Its findings underscore both the value and the complexity of genetic testing in conditions such as Usher syndrome and RP.

A broad look at inherited retinal dystrophies in Poland

IRDs are a diverse group of genetic conditions that can lead to progressive vision loss. Retinitis pigmentosa is one of the most common forms, and it can occur on its own or as part of a syndrome such as Usher syndrome. Because many different genes can contribute to similar retinal findings, identifying the underlying cause can be challenging.

The Polish cohort included:

  • 159 participants with RP
  • 21 participants with Usher syndrome
  • 16 participants with cone-rod dystrophy
  • Four participants with Bardet-Biedl syndrome
  • Three participants with Leber congenital amaurosis

Researchers used WES, a method that examines the protein-coding portions of a person’s genes. These regions contain many of the variants known to cause inherited disease. By analyzing exome data, the team sought to identify disease-causing genetic changes across the broad range of IRDs represented in the study.

Key genetic findings

Pathogenic variants were identified in 132 of the 203 participants, producing an overall diagnostic rate of 65.0%. In the group with RP-related disease, the diagnostic yield was 63.7%. In practical terms, genetic testing found a likely disease-causing change in nearly two-thirds of the people studied.

Two genes stood out in the cohort: ABCA4 and USH2A. Variants in ABCA4 accounted for 24% of the identified causative variants, while variants in USH2A accounted for 16%.

The prominence of USH2A is particularly meaningful in the context of Usher syndrome. USH2A is a well-recognized gene associated with Usher syndrome and inherited retinal disease. Its appearance among the most frequent causative genes in this Polish cohort reinforces the importance of including USH2A in genetic testing approaches for people with RP and syndromic retinal disease.

However, the study also highlights that no single gene explains all cases. The researchers identified 24 novel variants, meaning genetic changes not previously reported in this setting. These included different types of molecular changes, such as large deletions and frameshift variants. A frameshift variant disrupts how genetic instructions are read, potentially altering or preventing production of the usual protein. Large deletions remove a more substantial segment of genetic material.

This range of variant types illustrates the substantial genetic heterogeneity of IRDs: different people may have similar clinical diagnoses but very different underlying genetic causes.

Why whole-exome sequencing can be valuable

For patients and families, a genetic test is not simply a search for a label. It can help clarify the molecular basis of a retinal condition when clinical features overlap across multiple IRDs. This is especially relevant in syndromic disease, where retinal findings may be considered alongside other features, including hearing loss in Usher syndrome.

The study supports WES as a useful tool for molecular diagnosis in the Polish population. It also shows why testing strategies need to account for diverse variant types rather than focusing narrowly on a small number of common changes.

Based on the findings, the investigators plan to develop a dedicated gene panel for RP and related IRDs. A targeted panel informed by population-specific data could support more focused molecular diagnosis while retaining the genes most relevant to this clinical setting.

Implications for treatment research and care

This publication does not test a treatment. Its contribution is foundational: treatment research increasingly depends on knowing which gene is involved. A molecular diagnosis can help organize patients into genetically defined groups, an essential consideration for studies that investigate gene-specific or variant-informed approaches.

The researchers also collected clinical, imaging, and genetic information. These data may support future genotype-phenotype analyses, which examine how particular genetic findings relate to symptoms and retinal features. They may also enable phenotype-phenotype analyses, exploring patterns among clinical features themselves. Such work can improve understanding of why disease progression and presentation vary between individuals.

Looking ahead

The Polish WES study adds valuable population-specific evidence to the global IRD research landscape. Its results demonstrate that genetic diagnosis is achievable for many—but not all—people with inherited retinal disease, while also revealing previously unreported variants and considerable genetic diversity.

For the Usher syndrome community, the study reinforces a central message: precise genetic characterization matters. As genetic databases grow, dedicated testing panels are refined, and clinical and imaging data are linked with molecular findings, researchers will be better positioned to define disease subgroups and advance more personalized research pathways for IRDs.