March 2026 Research Update

This month, one clinical series adds a clearer picture of how the retina (the light-sensing layer at the back of the eye) can be affected in Sanfilippo syndrome, and what eye imaging tends to show. The main pattern was that many patients had changes in the outer parts of the retina near the center of vision, while the nerve fiber layer measured around the optic nerve often looked normal. This matters because it helps define what eye findings may be part of the condition, which can be useful when following changes over time. [1]

In 27 genetically confirmed patients, retinal imaging found parafoveal outer retinal degeneration (damage near, but not exactly at, the very center) in 59% of patients, and thickening of a foveal layer in 67%. The study also reported that retinal nerve fiber layer thickness was unremarkable across patients, suggesting that not all eye structures are affected in the same way. Patients with MPS IIIA were reported to have more severe retinal involvement, although the authors did not find a clean imaging pattern that separated all subtypes from each other. [1]

For patients and caregivers, this work mainly adds understanding of what eye tests may show in Sanfilippo syndrome and which parts of the retina may be more likely to change. It does not test a treatment, but it helps establish natural history information that may be useful for future studies that track whether the retina changes over time. What remains uncertain is how closely these imaging findings match a persons day-to-day vision symptoms and how quickly changes progress, since the report summarizes a single center experience with limited numbers in some subtypes. [1]

A new case report this month highlights that Sanfilippo type IIIC (MPS IIIC) can be recognized in adulthood and that confirming the diagnosis may depend on combining genetic testing with functional lab evidence. The report described two siblings diagnosed at ages 46 and 38, and it linked their symptoms to newly identified changes in the HGSNAT gene. This matters because it expands the known genetic causes of MPS IIIC and shows how lab testing can help interpret whether a newly found gene change is likely to be disease-causing. [2]

In these two adults, the authors identified two novel HGSNAT variants and then measured very low HGSNAT enzyme activity along with elevated urinary heparan sulfate (a urine marker related to the build-up seen in Sanfilippo). The siblings were described as having features such as hearing loss, eye disease (retinitis pigmentosa), and intellectual disability, alongside milder physical features. Together, the genetic findings plus the enzyme and urine results were used to support that the variants were pathogenic and to confirm the diagnosis. [2]

For families, this report mainly matters as evidence that MPS IIIC can sometimes be diagnosed later in life and that confirming a rare genetic finding may require more than DNA sequencing alone. This is early evidence from only 2 related people, so it cannot tell how common adult diagnosis is or predict outcomes for others, but it adds concrete examples of how novel gene changes can be evaluated using enzyme activity and a urine marker. It may matter more in the future as more families with similar variants are identified and compared. [2]