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Case Reports
. 2023 Jan 19;64(2):129-137.
doi: 10.1002/jmd2.12351. eCollection 2023 Mar.

Visual impairment in mucopolysaccharidosis VI

Augusto Monteiro Magalhães  1   2 , Ana Filipa Moleiro  1   3 , Esmeralda Rodrigues  2   4 , Sérgio Castro  5 , José Fonseca  5 , Elisa Leão-Teles  2
Affiliations
Case Reports

Visual impairment in mucopolysaccharidosis VI

Augusto Monteiro Magalhães et al. JIMD Rep. .

Abstract

Mucopolysaccharidosis (MPS) VI is a rare genetic disease characterized by deficient activity of N-acetylgalactosamine 4-sulfatase, leading to the systemic deposition of glycosaminoglycans. Ocular involvement is classically characterized by progressive corneal clouding, ocular hypertension (OHT), and optic neuropathy. Although corneal clouding can be solved with penetrating keratoplasty (PK), visual impairment usually remains, being frequently attributed to glaucoma. The purpose of this study was to retrospectively describe a series of MPS VI patients with optic neuropathy in order to deepen the knowledge regarding the causes of severe visual impairment among these patients. We present five genetically confirmed clinical cases of MPS VI, treated with enzymatic replacement therapy, and with regular systemic and ophthalmologic follow-up. Corneal clouding was a common early presenting feature, leading to PK in four patients. During their follow-up, all patients developed very low visual acuities regardless of corneal grafts outcomes and controlled intraocular pressure (IOP). Furthermore, all patients exhibited optic atrophy and imagiological evidence of significant subarachnoid space enlargement and consequent optic nerve thickness reduction, suggesting compression of the optic nerve in a retro-ocular location as the cause of optic neuropathy. Although optic neuropathy in MPS VI is commonly attributed to glaucoma due to OHT, by describing a series of five MPS VI patients, we provided evidence that, differently from glaucoma, compression of optic nerve in a retro-ocular location is crucial for the development of optic neuropathy, at least in some cases. We propose the denomination of posterior glaucoma and suggest it as an important cause of optic neuropathy, leading to severe visual impairment and blindness among these patients.

Keywords: blindness; glaucoma; mucopolysaccharidosis VI; ocular involvement; optic neuropathy; posterior glaucoma.

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Conflict of interest statement

Augusto Monteiro Magalhães received a speaker honorarium from Biomarin. Elisa Leão‐Teles received support to attend scientific meetings, consulting fees, or speaker honoraria from Sanofi Genzyme, Biomarin, and Takeda. Ana Filipa Moleiro, Esmeralda Rodrigues, Sérgio Castro, and José Fonseca declare that they have no conflict of interest.

Figures

FIGURE 1
FIGURE 1
Optic nerve retinography of (A) right and (B) left eyes of patient number 1, highlighting optic disk pallor with no significant cupping
FIGURE 2
FIGURE 2
T2‐fat saturation MRI for patient 1 showing enlarged perioptic subarachnoid space. (A) Axial section; (B) coronal section; (C) sagittal section
FIGURE 3
FIGURE 3
T2‐fat saturation MRI for patient 2 showing enlarged subarachnoid space with the “sausage” sign in sagittal section. (A) Axial section; (B) coronal section; (C) sagittal section
FIGURE 4
FIGURE 4
T2‐fat saturation MRI for patient 3 showing exuberant enlargement of subarachnoid space with “sausage” sign in axial section and reduced thickness of optic nerves, more pronounced on the left. (A) Axial section; (B) coronal section; (C) sagittal section
FIGURE 5
FIGURE 5
T2 ponderation MRI for patient 4 with evidence of enlargement of perioptic subarachnoid space. (A) Axial section. (B) Sagittal section
FIGURE 6
FIGURE 6
T2‐fat saturation MRI for patient 5 showing enlarged perioptic subarachnoid space with reduced optic nerve thickness. (A) Axial section; (B) coronal section; (C) sagittal section
See this image and copyright information in PMC

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