Retinal Phenotype in Mucopolysaccharidosis Type III.

Area of Science:

• Ophthalmology
• Genetics
• Rare Diseases

Background:

• Mucopolysaccharidosis type III (MPS III), or Sanfilippo syndrome, is a rare genetic disorder causing neurocognitive decline and early death.
• Visual impairment and retinal disease are common in MPS III, more so than in other MPS subtypes.

Purpose of the Study:

• To characterize the retinal phenotype in MPS III using advanced imaging techniques.
• To gain insights into the ocular disease progression in Sanfilippo syndrome.

Main Methods:

• A retrospective case series included 27 patients with genetically confirmed MPS III (IIIA, IIIB, IIIC).
• Spectral-domain optical coherence tomography (SD-OCT) analyzed retinal thickness and nerve fiber layer.
• Best-corrected visual acuity, slit lamp microscopy, and fundoscopy were performed as feasible.

Main Results:

• Parafoveal outer retinal layer degeneration was observed in 59% of patients.
• Foveal thickening of the external limiting membrane was noted in 67% of patients.
• MPS IIIA patients exhibited the most severe retinal abnormalities, including atrophy and fluid accumulation.

Conclusions:

• A consistent pattern of parafoveal outer retinal degeneration exists across all MPS III subtypes.
• MPS IIIA patients demonstrate the most significant retinal involvement, correlating with their rapid neurocognitive decline.
• These findings support systematic ophthalmological examinations for MPS III patients and inform future clinical trial design.