Novel Fundoscopic Features in Mucopolysaccharidosis Type VI: Multimodal Evaluation of Scleral Deposits

Mucopolysaccharidosis type VI (MPS VI) is a rare inherited metabolic disorder, primarily attributed to the deficiency of the enzyme N-acetylgalactosamine-4-sulfatase, responsible for the degradation of dermatan sulfate and chondroitin-4-sulfate. Therefore, there is a widespread accumulation of partially degraded glycosaminoglycans. Corneal opacification is the hallmark ocular feature in the MPS. Retinal and scleral involvement in this MPS is extremely rare. The purpose of this work was to describe novel fundoscopic alterations present in patients with MPS VI.

This is a case series involving three non-related patients referred to our department from the Unit of Inherited Metabolic Diseases. Multimodal imaging was performed in every patient. Fundus photography and enhanced depth imaging optical coherence tomography (EDI-OCT) were performed. Multiple areas of yellow/orange patches were observed on fundus photography, corresponding to areas in which deposits of intermediate reflectivity in the EDI-OCT could be seen at the scleral level with associated choroidal thinning. This finding suggested the presence of scleral deposits of glycosaminoglycans.

To our knowledge, this is the first case series in the literature encompassing patients with MPS VI with suspected deposits of glycosaminoglycans in the sclera. The better control of the systemic comorbidities, the increase in life expectancy, and the timely management of corneal disease have allowed the identification of new, late-onset ocular manifestations in MPS patients. In addition, new imaging techniques have introduced the possibility of better characterizing and understanding these manifestations.