Bilateral Foveal Cysts in Mucopolysaccharidosis Type I (Hurler Syndrome): Response to Acetazolamide With Insights From Multimodal Retinal Imaging and Electrophysiology.

OBJECTIVE

The aim of this study is to report a case of bilateral foveal cysts in MPS I-H resolving with oral acetazolamide and to highlight the diagnostic value of multimodal retinal imaging and electrophysiological testing.

INTRODUCTION

Hurler syndrome (mucopolysaccharidosis Type I-H) is a lysosomal storage disorder that can cause progressive multisystem complications. Retinal involvement often mimics retinitis pigmentosa (RP), and pathology may progress even after early hematopoietic stem cell transplantation (HSCT) due to limited enzyme penetration into ocular tissues.

CASE SUMMARY: A 17-year-old female with MPS I-H, post-HSCT at 21 months, presented with bilateral visual decline despite a normal clinical fundus exam. Evaluation included spectral-domain OCT (SD-OCT), fundus autofluorescence (FAF), multifocal electroretinography (mfERG), full-field ERG (ffERG), and visual evoked potential. SD-OCT revealed bilateral intraretinal foveal cysts without leakage on fluorescein angiography. FAF showed a bull's eye maculopathy pattern; mfERG showed bilateral macular dysfunction. ffERG revealed rod-cone dystrophy. Two 3-month courses of oral acetazolamide (125 mg three times daily) led to complete cyst resolution and visual improvement.

CONCLUSION

This case supports the role of systemic carbonic anhydrase inhibitors in treating nonleaking macular cysts in MPS I, similar to RP-related cystoid macular pathologies, and highlights the value of integrating electrophysiological and multimodal imaging, especially in occult retinal disease.