IDUA gene variants linked to isolated retinitis pigmentosa

A single genetic finding can quietly reframe how clinicians read a diagnosis. That is what a new study in the American Journal of Human Genetics suggests is happening with a subset of retinitis pigmentosa cases.

Researchers identified that hypomorphic variants in the IDUA gene — variants that reduce, but do not eliminate, protein function — are associated with retinitis pigmentosa in people who show none of the broader features of mucopolysaccharidosis type I (MPS I), the study reported. MPS I is a metabolic disorder typically characterised by skeletal, cardiac, and neurological involvement alongside vision loss. In these patients, only the eye disease presented.

The study found that the residual enzyme activity left by these low-impact variants appears sufficient to protect most organ systems, while leaving the retina vulnerable, according to the researchers. Functional experiments were used to measure how each variant affected both gene expression and enzyme activity levels, the study reported.

What the findings describe

The investigators characterised each variant's functional consequence and used those measurements to estimate the threshold of IDUA activity below which retinal disease emerges, the study said. The implication is that some patients currently diagnosed with non-syndromic retinitis pigmentosa — meaning no known syndrome underlies their vision loss — may carry an underlying lysosomal storage disorder that has gone unrecognised.

Hypomorphic variants, by definition, are partial loss-of-function changes. They sit below the threshold that produces classical MPS I but, the study suggests, above the threshold that fully protects the retina.

Why this matters for the community

Retinitis pigmentosa is one of the more common causes of progressive vision loss in adults, and a significant proportion of cases carry no genetic explanation. For people with albinism, who already navigate complex overlapping challenges to vision, the possibility that a metabolic gene may contribute to some apparently isolated retinal conditions adds a layer of diagnostic complexity worth tracking.

The research does not directly address albinism. But lysosomal storage pathways and pigmentation biology share enough metabolic territory that findings about retinal vulnerability in the context of enzyme insufficiency are worth the community's attention.

Clinicians evaluating unexplained retinitis pigmentosa, the study suggested, may now have grounds to consider IDUA sequencing even when systemic MPS I features are absent.

The paper was published in the American Journal of Human Genetics. The precise patient cohort size and full author list were not included in the summary available for this report.