Electroretinographic and Optical Coherence Tomographic Characteristics of Mucopolysaccharidosis Type I Hurler and I Hurler-Scheie
Stephanie N. Kletke, MD; Ajoy Vincent, MD; Eoghan Millar, MBChB, FRCOphth; Asim Ali, MD, FRCSC
Department of Ophthalmology and Vision Sciences, The Hospital for Sick Children; Department of Ophthalmology and Vision Sciences, University of Toronto
Toronto, Ontario, Canada
Introduction: To describe the clinical, electroretinography (ERG) and spectral-domain optical coherence tomography (SD-OCT) findings in mucopolysaccharidosis (MPS) type I.
Methods: Fourteen children (50% female) with MPS I Hurler (I-H, n=11) and Hurler-Scheie (I-H/S, n=3) who had ERG and SD-OCT were identified and retrospectively reviewed.
Results: Diagnosis was confirmed by IDUA mutational analysis (n=9) or alpha-L-iduronidase deficiency (n=5). Children with MPS I-H had hematopoietic stem cell transplant (mean 1.22 years) and I-H/S received enzyme replacement (mean age 4.69 years). All children had diffuse ground glass stromal opacities, 9 requiring deep anterior lamellar keratoplasty. At the initial ERG (mean 10.10 years, range: 1.58 – 17.92), mean visual acuity was 0.70 logMAR (range: 0.3 – 1.6) and mean cycloplegic spherical equivalent was +1.79 D (range: -25.00 to +8.75). Mean initial standard flash b/a ratio was 1.13 (range: 0.37-3.58). Eleven cases had at least one electronegative ERG. Four children had maculopathy, but none showed peripheral pigmentary retinopathy. SD-OCT demonstrated central macular external limiting membrane (ELM) thickening in all cases.
Discussion: Corneal opacities and macular ELM thickening were found in all children with MPS I-H and I-H/S. Reduced b/a ratio was common at initial ERG and 79% had at least one electronegative ERG. Macular ELM thickening was observed prior to any clinically apparent retinal changes.
Conclusion: Despite systemic therapy, micro-structural and functional retinal changes are uniformly seen in MPS I prior to clinically apparent retinal changes. The presence of an electronegative ERG represents a post-transductional abnormality, which could be explained by ELM thickening.
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