The ocular features of the mucopolysaccharidoses

Clinical and imaging strategies for the assessment of the ocular side effects of systemic targeted anti-cancer therapies

Systemic targeted anti-cancer therapies selectively target cancerous cells whilst limiting systemic side effects. The eye however, is a particularly sensitive organ and the expanding use of the newer targeted chemotherapy agents has been associated with multiple ocular side effects. In this review we provide an update of the ocular side effects of the newer targeted chemotherapy agents along with suggested minimum, pragmatic, evidence-based strategies for effective screening or monitoring for potential ocular side effects. This framework is designed to guide oncologists, trial managers, protocol developers and regulatory authorities so that appropriate ophthalmic clinical examinations and non-invasive modern imaging can be requested and commissioned according to a patient's specific treatment.

Retinopathy in Mucopolysaccharidoses

PURPOSE

To determine the pattern(s) of onset, variation, and progression of retinopathy in patients with mucopolysaccharidoses (MPS).

DESIGN

Prospective, longitudinal, observational study.

PARTICIPANTS

Between November 2015 and March 2023, individuals with MPS were recruited from ophthalmology clinics at the Manchester Royal Eye Hospital, United Kingdom.

METHODS

Participants underwent assessment of visual acuity, corneal clouding, and intraocular pressure, along with fundoscopy, ultrawidefield (UWF) color fundus photography, fundus autofluorescence (FAF) imaging, OCT, and electroretinography (ERG), where feasible.

MAIN OUTCOME MEASURES

Evaluation of findings from clinical examination, retinal imaging, and ERG studies to ascertain the presence and patterns of retinopathy.

RESULTS

Data were collected for 75 patients, including 45 with MPS I, 9 with MPS II, 13 with MPS IVA, and 8 with MPS VI, aged 3 to 53 years. Fundus photography was conducted in 65 patients, FAF in 61 patients, OCT in 58 patients, and electrodiagnostic studies in 36 patients. Retinopathy was defined as signs of retinal disease evident through retinal examination or fundus photography, such as depigmentation, bone-spicule pigmentation, vascular tortuosity, retinal pigment epithelium (RPE) mottling/other changes, macular atrophy/puckering/epiretinal membranes, FAF findings such as a central hyperautofluorescent dot, hyperautofluorescent parafoveal ring, hypoautofluorescent lesions around fovea (double bull's eye), areas of hyper/hypoautofluorescence, and extrafoveal changes, OCT imaging features such as central external limiting membrane (ELM) thickening, RPE disturbance, photoreceptor layer loss, parafoveal retinal atrophy, and outer retinal/intrachoroidal cavities, or ERG studies revealing rod-mediated retinopathy or rod-cone dystrophy. Retinopathy was confirmed in 32 patients, including 25 with MPS I, 4 with MPS II, 1 with MPS IVA, and 2 with MPS VI. Five participants were first diagnosed with retinopathy with clinical examination, and 31 participants were identified on UWF color fundus photography supported by FAF and OCT. A total of 21 patients exhibited ERG abnormalities consistent with retinopathy. Fifteen of the total 32 participants described symptoms of nyctalopia. The onset of retinopathy varied substantially, with initial detection between 2 and 53 years of age.

CONCLUSIONS

Patients with MPS as young as 2 years may develop retinopathy, diagnosed through fundus examination, ophthalmic imaging, or ERG. Emerging treatments, including gene therapy, may prevent or stabilize retinopathy. Phenotypic data and natural history of MPS-related retinopathy are thus of paramount importance.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

Histopathological and Clinical-Genetic Analysis of Corneal Specimens in Maroteaux-Lamy Syndrome

PURPOSE

Maroteaux-Lamy syndrome (MPSVI) is a rare lysosomal storage disorder caused by an Arylsulfatase B (ARSB) deficiency, leading to dermatan sulfate and chondroitin-4-sulfate accumulation. It manifests various systemic clinical features. Enzyme Replacement Therapy with Galsulfase (Naglazyme) manages systemic symptoms, but ocular manifestations, such as corneal opacity, often require surgery. This study examines histopathological features of corneas in patients with MPSVI who underwent penetrating keratoplasty (PK).

METHODS

A retrospective study of 3 patients with MPSVI included demographics, genetics, clinical history, and ophthalmological findings. Six corneas were analyzed with hematoxylin-eosin and histochemical stains, focusing on structural changes and glycosaminoglycan (GAG) deposition.

RESULTS

All patients, diagnosed between ages 16 months and 11 years, exhibited multisystem involvement. All had corneal clouding because of GAG accumulation, with PK performed between ages 14 and 22. Visual improvement was limited by optic nerve atrophy despite Enzyme Replacement Therapy. Histopathological analysis revealed hydropic-like changes in basal keratinocytes, intracytoplasmic and subepithelial GAG deposits, and thinned Bowman layer disruption. The stroma displayed elongated deposits, whereas Descemet membrane showed thinning without GAG deposits. Endothelium GAG deposits were also identified.

CONCLUSIONS

The study highlights the alterations in various corneal layers, which have seldom been reported on Maroteaux-Lamy syndrome. Nonetheless, the GAG deposits identified and the changes in Bowman layer align with the literature. PK temporarily improved corneal clarity. However, long-term visual outcomes were poor because of optic nerve damage. Early diagnosis and multidisciplinary management are essential to improve outcomes.

Syndromic Retinitis Pigmentosa

Retinitis pigmentosa (RP) is a progressive inherited retinal dystrophy, characterized by the degeneration of photoreceptors, presenting as a rod-cone dystrophy. Approximately 20-30% of patients with RP also exhibit extra-ocular manifestations in the context of a syndrome. This manuscript discusses the broad spectrum of syndromes associated with RP, pathogenic mechanisms, clinical manifestations, differential diagnoses, clinical management approaches, and future perspectives. Given the diverse clinical and genetic landscape of syndromic RP, the diagnosis may be challenging. However, an accurate and timely diagnosis is essential for optimal clinical management, prognostication, and potential treatment. Broadly, the syndromes associated with RP can be categorized into ciliopathies, inherited metabolic disorders, mitochondrial disorders, and miscellaneous syndromes. Among the ciliopathies associated with RP, Usher syndrome and Bardet-Biedl syndrome are the most well-known. Less common ciliopathies include Cohen syndrome, Joubert syndrome, cranioectodermal dysplasia, asphyxiating thoracic dystrophy, Mainzer-Saldino syndrome, and RHYNS syndrome. Several inherited metabolic disorders can present with RP including Zellweger spectrum disorders, adult Refsum disease, α-methylacyl-CoA racemase deficiency, certain mucopolysaccharidoses, ataxia with vitamin E deficiency, abetalipoproteinemia, several neuronal ceroid lipofuscinoses, mevalonic aciduria, PKAN/HARP syndrome, PHARC syndrome, and methylmalonic acidaemia with homocystinuria type cobalamin (cbl) C disease. Due to the mitochondria's essential role in supplying continuous energy to the retina, disruption of mitochondrial function can lead to RP, as seen in Kearns-Sayre syndrome, NARP syndrome, primary coenzyme Q10 deficiency, SSBP1-associated disease, and long chain 3-hydroxyacyl-CoA dehydrogenase deficiency. Lastly, Cockayne syndrome and PERCHING syndrome can present with RP, but they do not fit the abovementioned hierarchy and are thus categorized as 'Miscellaneous'. Several first-in-human clinical trials are underway or in preparation for some of these syndromic forms of RP.

A Novel Symptomatic Lecithin-Cholesterol Acyltransferase Gene Mutation With Corneal Amyloidosis

PURPOSE

To present ocular clinical, histological, systemic, and genetic findings of a patient with familial lecithin-cholesterol acyltransferase (LCAT) deficiency caused by a novel genetic variant of the LCAT gene associated with secondary corneal amyloidosis.

METHODS

Case report.

RESULTS

A 74-year-old woman presented with decreased visual acuity (VA), sensitivity to light, and progressive whitening of both corneas for approximately 20 years. The patient had undergone penetrating keratoplasty (PKP) on the right eye 6 years ago. Ophthalmologic examination revealed decreased VA in both eyes (OD: 0.05, OS: 0.3), and even further reduced glare VA (OD: 0.05, OS: 0.1), diffuse whitish corneal opacity involving the total thickness of the corneal stroma without crystalline deposits, and a marked peripheral diffuse arcus. Systemic examination revealed severely reduced plasma high-density lipoprotein cholesterol levels, target cells in blood smear, and chronic normochromic anemia. Clinically, LCAT deficiency was the most likely diagnosis. Further genetic analysis confirmed the diagnosis. The patient is homozygous for the novel variant c.943T>C (p.Trp315Arg) in the LCAT gene. Histologic examination of the cornea removed during the first keratoplasty revealed amyloid deposits. The cornea removed at the second keratoplasty had small vacuoles in the anterior stroma, indicating recurrence of lipid deposition.

CONCLUSIONS

LCAT deficiency is a rare genetic disorder that can cause corneal opacities because of lipid deposition in the cornea. Systemic manifestations may help in the differential diagnosis to other diseases associated with severe high-density lipoprotein cholesterol reduction. Genetic analysis is employed to confirm the diagnosis. Some mutations in the LCAT gene seem to be associated with secondary corneal amyloidosis. Further investigation of this association is warranted. A recurrence of corneal opacity after PKP seems to occur mainly in the anterior corneal stroma.

Expanding the phenotypic and genotypic spectrum of patients with HGSNAT-related retinopathy

BACKGROUND

Variants in HGSNAT have historically been associated with syndromic mucopolysaccharidosis type IIIC (MPSIIIC) but more recent studies demonstrate cases of HGSNAT-related non-syndromic retinitis pigmentosa. We describe and expand the genotypic and phenotypic spectrum of this disease.

MATERIALS AND METHODS

This is a retrospective, observational, case series of 11 patients with pericentral retinitis pigmentosa due to variants in HGSNAT gene without a syndromic diagnosis of MPSIIIC. We reviewed ophthalmologic data extracted from medical records, genetic testing, color fundus photos, fundus autofluorescence (FAF), and optical coherence tomography (OCT).

RESULTS

Of the 11 patients, the mean age was 52 years (range: 26-78). The mean age of ophthalmologic symptoms onset was 45 years (range: 15-72). The visual acuity varied from 20/20 to 20/80 (mean 20/30 median 20/20). We described five novel variants in HGSNAT: c.715del (p.Arg239Alafs *37), c.118 G>A (p.Asp40Asn), c.1218_1220delinsTAT, c.1297A>G (p.Asn433Asp), and c.1726 G>T (p.Gly576*).

CONCLUSIONS

HGSNAT has high phenotypic heterogeneity. Data from our cohort showed that all patients who had at least one variant of c.1843 G>A (p.Ala615Thr) presented with the onset of ocular symptoms after the fourth decade of life. The two patients with onset of ocular symptoms before the fourth decade did not carry this variant. This may suggest that c.1843 G>A variant is associated with a later onset of retinopathy.

Changes in Corneal Clouding Over Time in Patients With Mucopolysaccharidosis

PURPOSE

Mucopolysaccharidoses (MPSs) are a rare group of lysosomal storage disorders characterized by the accumulation of incompletely degraded glycosaminoglycans (GAGs) in multiple organ systems, including the eye. Visual loss occurs in MPS predominantly due to corneal clouding. Despite the success of enzyme replacement therapy (ERT) and hematopoietic stem cell transplantation (HSCT) in improving many systemic manifestations of MPS, less is known about their effect on corneal clouding. This study prospectively analyses the effect of both ERT and HSCT on corneal clouding using objective measures over time.

METHODS

This is a prospective longitudinal observational study. Corneal clouding was assessed in each participant using slitlamp, digital slit-lamp photographs, and an iris camera (Corneal Opacification Measure [COM] and the Pentacam system).

RESULTS

Data were collected for 65 participants: 39 MPS I (Hurler), 5 MPS II (Hunter), 12 MPS IV (Morquio), and 9 MPS VI (Maroteaux-Lamy). Follow-up data are available for 45 participants (29 MPS I, 3 MPS II, 6 MPS IV, and 7 MPS VI).

CONCLUSIONS

This study found corneal clouding to be stable in most participants with MPS I, II, IV, and VI over a follow-up period of 5 to 75 months (median of 30 months) when measured with clinical corneal grading systems, graded digital slit-lamp images, and iris camera COMs. For those with Pentacam densitometry measures, there was a progression of corneal clouding, on average, in those with MPS I and MPS VI. There was no apparent difference in progression of corneal clouding between patients who were on ERT, HSCT, or no treatment.

Small leucine rich proteoglycans: Biology, function and their therapeutic potential in the ocular surface

Small leucine rich proteoglycans (SLRPs) are the largest family of proteoglycans, with 18 members that are subdivided into five classes. SLRPs are small in size and can be present in tissues as glycosylated and non-glycosylated proteins, and the most studied SLRPs include decorin, biglycan, lumican, keratocan and fibromodulin. SLRPs specifically bind to collagen fibrils, regulating collagen fibrillogenesis and the biomechanical properties of tissues, and are expressed at particularly high levels in fibrous tissues, such as the cornea. However, SLRPs are also very active components of the ECM, interacting with numerous growth factors, cytokines and cell surface receptors. Therefore, SLRPs regulate major cellular processes and have a central role in major fundamental biological processes, such as maintaining corneal homeostasis and transparency and regulating corneal wound healing. Over the years, mutations and/or altered expression of SLRPs have been associated with various corneal diseases, such as congenital stromal corneal dystrophy and cornea plana. Recently, there has been great interest in harnessing the various functions of SLRPs for therapeutic purposes. In this comprehensive review, we describe the structural features and the related functions of SLRPs, and how these affect the therapeutic potential of SLRPs, with special emphasis on the use of SLRPs for treating ocular surface pathologies.

Long term follow-up after haematopoietic stem cell transplantation for mucopolysaccharidosis type I-H: a retrospective study of 51 patients

Mucopolysaccharidosis type I-H (MPS I-H) is a rare lysosomal storage disorder caused by α-L-Iduronidase deficiency. Early haematopoietic stem cell transplantation (HSCT) is the sole available therapeutic option to preserve neurocognitive functions. We report long-term follow-up (median 9 years, interquartile range 8-16.5) for 51 MPS I-H patients who underwent HSCT between 1986 and 2018 in France. 4 patients died from complications of HSCT and one from disease progression. Complete chimerism and normal α-L-Iduronidase activity were obtained in 84% and 71% of patients respectively. No difference of outcomes was observed between bone marrow and cord blood stem cell sources. All patients acquired independent walking and 91% and 78% acquired intelligible language or reading and writing. Intelligence Quotient evaluation (n = 23) showed that 69% had IQ ≥ 70 at last follow-up. 58% of patients had normal or remedial schooling and 62% of the 13 adults had good socio-professional insertion. Skeletal dysplasia as well as vision and hearing impairments progressed despite HSCT, with significant disability. These results provide a long-term assessment of HSCT efficacy in MPS I-H and could be useful in the evaluation of novel promising treatments such as gene therapy.

Visual impairment in mucopolysaccharidosis VI

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.

Clinical and pathological characterization of ophthalmic disease in a canine model of mucopolysaccharidosis type I

Mucopolysaccharidosis type I (MPS I) is a rare lysosomal storage disease caused by α-L-iduronidase enzyme deficiency, resulting in glycosaminoglycan (GAG) accumulation in various cell types, including ocular tissues. Ocular manifestations in humans are common with significant pathological changes including corneal opacification, retinopathy, optic nerve swelling and atrophy, and glaucoma. Available treatments for MPS I are suboptimal and there is limited to no effect in treating the ocular disease. The goal of this study was to characterize the clinical and pathological features of ocular disease in a line of MPS I affected dogs, including changes not previously reported. A total of 22 dogs were studied; 12 MPS I were affected and 10 were unaffected. A subset of each underwent complete ophthalmic examination including slit lamp biomicroscopy, indirect ophthalmoscopy, rebound tonometry, and ultrasonic pachymetry. Globes were evaluated microscopically for morphological changes and GAG accumulation. Clinical corneal abnormalities in affected dogs included edema, neovascularization, fibrosis, and marked stromal thickening. Intraocular pressures were within reference interval for affected and unaffected dogs. Microscopically, vacuolated cells containing alcian blue positive inclusions were detected within the corneal stroma, iris, ciliary body, sclera, and optic nerve meninges of affected dogs. Ganglioside accumulation was identified by luxol fast blue staining in rare retinal ganglion cells. Increased lysosomal integral membrane protein-2 expression was demonstrated within the retina of affected animals when compared to unaffected controls. Results of this study further characterize ocular pathology in the canine model of MPS I and provide foundational data for future therapeutic efficacy studies.

Retinitis pigmentosa and nanophthalmos in a patient with attenuated Hunter's syndrome

PURPOSE

To describe a case of retinitis pigmentosa and nanophthalmos in a patient with attenuated Hunter's syndrome.

METHODS

Fundus photography, total field electroretinogram, ultrasound, computerized visual field examination, biochemical examination and genetic testing were obtained.

RESULTS

The fundus exam showed diffuse arteriolar attenuation, optic disc with regular contours, and pigment agglomerates like "bone spicules" in the middle periphery. Ultrasound examination revealed scleral thickening and short axial diameter in both eyes. The total field electroretinogram exam showed a subnormal result with greater impairment of the scotopic phase of the exam. Computerized visual field examination demonstrated a diffuse reduction in retinal sensitivity in the periphery. Biochemical examination showed increased urine glycosaminoglycan excretion and iduronate-2-sulphatase activity (IDS) deficiency in leukocytes, confirming the type II mucopolysaccharidosis. Molecular analysis revealed a novel missense mutation (p.A77D) in the IDS gene.

CONCLUSION

The case report is about a patient presented an attenuated form of the syndrome, with no cognitive impairment. Ophthalmologic follow-up is still an important part of multidisciplinary treatment for Hunter's syndrome.

Ocular Manifestations of Hurler-Scheie Syndrome: Recurrence of Host Disease in the Corneal Transplant

Introduction

Hurler-Scheie syndrome is a type of mucopolysaccharidosis I (MPS). In MPS I the decreased activity of alpha-L-iduronidase lysosomal enzyme leads to glycosaminoglycan (GAG) deposition in the intra- and extracellular matrix. Excessive amounts of GAG can accumulate in most layers of the cornea, including epithelial cells, stromal keratocytes, and endothelial cells.

Case Presentation

A 25-year-old female patient suffering from Hurler-Scheie syndrome with multiple ocular manifestations is reported. Due to significant bilateral corneal opacification, penetrating keratoplasty was performed on both eyes. Histopathologic examination of the corneal buttons showed disorganized collagen fibers with heterogenous thickness and many granule-containing keratocytes with excessive cytoplasm. Despite receiving enzyme replacement therapy, in vivo confocal microscopy revealed characteristic vacuoles in the basal epithelium and corneal stroma 96 months after transplantation. High resolution anterior segment optical coherence tomography demonstrated hyperreflective opacities superficial and deeper in the stroma which was consistent with recurrence of host disease in the graft.

Conclusion

To the best of our knowledge, this is the first documented Hurler-Scheie syndrome case of recurrence after penetrating keratoplasty demonstrated by in vivo confocal microscopy. Additionally, this patient manifested severe ocular involvement of MPS which might be an explanation of the progressive course of corneal opacification after transplantation.

Mucopolysaccharidosis Type 1 among Children-Neuroradiological Perspective Based on Single Centre Experience and Literature Review

Mucopolysaccharidosis 1 (MPS 1) is a group of rare lysosomal genetic disorders resulting from the accumulation of undegraded glycosaminoglycans (GAGs) leading to multiorgan damage. Neurological symptoms vary from mild to severe. Neuroimaging-mainly magnetic resonance (MRI)-plays a crucial role in disease diagnosis and monitoring. Early diagnosis is of the utmost importance due to the necessity of an early therapy implementation. New imaging tools like MR spectroscopy (MRS), semiquantitative MRI analysis and applying scoring systems help substantially in MPS 1 surveillance. The presented analysis of neuroimaging manifestations is based on 5 children with MPS 1 and a literature review. The vigilance of the radiologist based on knowledge of neuroradiological patterns is highlighted.

Objectively measuring anterior segment alterations in the eyes of mucopolysaccharidoses: Its utility in early diagnosis of glaucoma

Purpose

Our study aimed to evaluate the utility of the anterior segment morphometry for objectively assessing anterior segment architectural changes of corneal clouding in the mucopolysaccharidoses (MPS) cohort and to investigate whether these measurements correlate with the slit-lamp findings on the cornea and early diagnosis of glaucoma.

Methods

This retrospective study involved 70 eyes of 35 children with cloudy cornea due to MPS variants. Anterior segment architectural alterations were measured using anterior segment imaging and biometry in MPS children and compared with controls.

Results

Mean age of the cohort at the time of assessment was 7.9 ± 4.5 years. Males constituted two-thirds of the cohort. Variants of MPS with cloudy cornea were as follows: Type I (62%), Type IV (11%), and Type VI (22%). Morphometric measurements were available in 22 eyes of 11 MPS children and an age-matched healthy control group. There were significant differences between MPS cohort and controls in refraction in Diopters (5.03 ± 0.39 and 0.01 ± 0.04; P < 0.0001), axial length (AXL) in mm (21.39 ± 0.28 and 23.04 ± 0.28; P = 0.0002), average keratometry in Diopters (40.67 ± 0.44 and 42.83 ± 0.44; P < 0.0001), anterior chamber depth (ACD) in mm (2.92 ± 0.07 and 3.65 ± 0.07; P < 0.0001), and intraocular pressure (IOP) in mmHg (25.2 ± 2.0 and 14.1 ± 2.3; P = 0.0003). Secondary glaucoma was observed in 28% of the MPS cohort.

Conclusion

The anterior segment morphometry in the cloudy cornea due to MPS provides an objective measurement of anterior segment architectural changes, thus diagnosing early-onset secondary glaucoma. These findings highlight that cloudy cornea due to MPS variants merits close monitoring throughout life.

Autophagy in the retinal pigment epithelium: a new vision and future challenges

The retinal pigment epithelium (RPE) is a highly specialized monolayer of polarized, pigmented epithelial cells that resides between the vessels of the choriocapillaris and the neural retina. The RPE is essential for the maintenance and survival of overlying light-sensitive photoreceptors, as it participates in the formation of the outer blood-retinal barrier, phagocytosis, degradation of photoreceptor outer segment (POS) tips, maintenance of the retinoid cycle, and protection against light and oxidative stress. Autophagy is an evolutionarily conserved 'self-eating' process, designed to maintain cellular homeostasis. The daily autophagy demands in the RPE require precise gene regulation for the digestion and recycling of intracellular and POS components in lysosomes in response to light and stress conditions. In this review, we discuss selective autophagy and focus on the recent advances in our understanding of the mechanism of cell clearance in the RPE for visual function. Understanding how this catabolic process is regulated by both transcriptional and post-transcriptional mechanisms in the RPE will promote the recognition of pathological pathways in genetic disease and shed light on potential therapeutic strategies to treat visual impairments in patients with retinal disorders associated with lysosomal dysfunction.

Novel chorioretinal findings in two siblings with mucopolysaccharidosis type VI

PURPOSE

To describe and compare the systemic and ocular findings in two siblings with mucopolysaccharidosis type VI (Maroteaux-Lamy syndrome), one treated with recombinant galsulfase, and one who was untreated.

METHOD

One female patient aged 33 years (case 1) who had received galsulfase enzyme replacement therapy for 11 years, and her younger male sibling by 3 years (case 2), who had declined systemic treatment, underwent clinical ophthalmic examination and retinal ocular coherence tomography. The female sibling underwent electrophysiology testing of visual function.

RESULTS

Case 1 had best corrected visual acuity right 6/4.8 and left 6/6. Case 2 had best corrected visual acuity of 6/6 in each eye. Case 1 had bilateral mild corneal haze and a clinically unremarkable posterior segment examination. Case 2 had bilateral very mild corneal haze and retinal striae on examination. Ocular coherence tomography showed choroidal folds at the maculae in both patients, more pronounced in Case 2, who also had retinal folds and epiretinal membrane. Electroretinography showed very mild involvement of the rods only in Case 1.

CONCLUSION

These two siblings with mucopolysaccharidosis type VI, one treated and one untreated, displayed variable levels of systemic, corneal, and chorioretinal involvement in their disease Further studies of choroidal changes in MPS VI may prove useful as a biomarker of ocular response to treatment outside the blood-retina barrier. Both patients have provided written consent to publish case details.

Pre-operative Considerations in Adult Mucopolysaccharidosis Patients Planned for Cardiac Intervention

Mucopolysaccharidoses (MPS) are rare lysosomal storage diseases characterized by multiorgan involvement and shortened longevity. Due to advances in therapies such as enzyme replacement therapy and haematopoietic stem cell therapy, life expectancy has increased posing newer challenges to patients and health professionals. One such challenge is cardiovascular manifestations of MPS, which can be life limiting and cause reduction in quality of life. Any cardiovascular intervention mandates comprehensive, multi-systemic work-up by specialist teams to optimize outcome. We highlight the importance of multidisciplinary evaluation of adult MPS patients requiring cardiovascular intervention. Clinical assessments and investigations are discussed, with a focus on the cardiac, anesthetic, airway, respiratory, radiological and psychosocial factors.

Non-cardiac Manifestations in Adult Patients With Mucopolysaccharidosis

Mucopolysaccharidoses (MPS) are a heterogeneous group of disorders that results in the absence or deficiency of lysosomal enzymes, leading to an inappropriate storage of glycosaminoglycans (GAGs) in various tissues of the body such as bones, cartilage, heart valves, arteries, upper airways, cornea, teeth, liver and nervous system. Clinical manifestations can become progressively exacerbated with age and affect their quality of life. Developments in advanced supportive treatment options such as enzyme replacement therapy (ERT), hematopoietic stem cell transplantation (HSCT) may have improved patients' life span. Adult MPS patients require specialist clinical surveillance long-term. In many cases, in addition to the MPS-related health problems, they may develop age-related complications. Considering the complexity of their clinical manifestations and lack of guidelines on the management of adult MPS disorders, multispecialty and multidisciplinary teams' care is essential to diagnose and treat health problems that are likely to be encountered. This review presents non-cardiac clinical manifestations, their pathophysiology, management and long-term outcomes in adult MPS patients.

Ocular phenotype and electroretinogram abnormalities in Lafora disease and correlation with disease stage

Background

Lafora disease (LD) is a neurodegenerative disorder featuring action and stimulus-sensitive myoclonus, epilepsy, and cognitive deterioration. Mutations in the EPM2A/EPM2B genes classically prove causative for the disease in most cases. Since full-field electroretinogram (ffERG) may reveal early-stage changes in a wide spectrum of diseases, we aimed to evaluate retinal cones and rods dysfunction in a cohort of Italian LD patients.

Methods

Patients with genetically confirmed LD were recruited and subjected to ffERG analysis following the International Society for Clinical Electrophysiology of Vision (ISCEV) protocol.

Results

Six patients aged between 13 and 26 years (mean 19.5 years) were included. The mean age at disease onset was 12.5 years with a mean disease duration of 7 years. The ffERG analysis revealed a global mild to severe generalized cones dysfunction in all patients. Linear correlation was identified between disease stage and the degree of cones and rods dysfunction, as well as between the type of mutation and the cones and rods dysfunction.

Conclusions

This study brings further evidence of early retinal alterations in LD patients. The cones and rods dysfunction grade is related to disease duration. The ffERG is an important tool to determine the disease stage, allowing to evaluate either natural or treatment-related disease progression in a minimally invasive way.

MPS VI associated ocular phenotypes in an MPS VI murine model and the therapeutic effects of odiparcil treatment

Maroteaux - Lamy syndrome (mucopolysaccharidosis type VI, MPS VI) is a lysosomal storage disease resulting from insufficient enzymatic activity for degradation of the specific glycosaminoglycans (GAG) chondroitin sulphate (CS) and dermatan sulphate (DS). Among the most pronounced MPS VI clinical manifestations caused by cellular accumulation of excess CS and DS are eye disorders, in particular those that affect the cornea. Ocular manifestations are not treated by the current standard of care, enzyme replacement therapy (ERT), leaving patients with a significant unmet need. Using in vitro and in vivo models, we previously demonstrated the potential of the β-D-xyloside, odiparcil, as an oral GAG clearance therapy for MPS VI. Here, we characterized the eye phenotypes in MPS VI arylsulfatase B deficient mice (Arsb^-) and studied the effects of odiparcil treatment in early and established disease models. Severe levels of opacification and GAG accumulation were detected in the eyes of MPS VI Arsb^- mice. Histological examination of MPS VI Arsb^- eyes showed an aggregate of corneal phenotypes, including reduction in the corneal epithelium thickness and number of epithelial cell layers, and morphological malformations in the stroma. In addition, colloidal iron staining showed specifically GAG accumulation in the cornea. Orally administered odiparcil markedly reduced GAG accumulation in the eyes of MPS VI Arsb^- mice in both disease models and restored the corneal morphology (epithelial layers and stromal structure). In the early disease model of MPS VI, odiparcil partially reduced corneal opacity area, but did not affect opacity area in the established model. Analysis of GAG types accumulating in the MPS VI Arsb^- eyes demonstrated major contribution of DS and CS, with some increase in heparan sulphate (HS) as well and all were reduced with odiparcil treatment. Taken together, we further reveal the potential of odiparcil to be an effective therapy for eye phenotypes associated with MPS VI disease.

Mucopolysaccharidosis Type VI, an Updated Overview of the Disease

Mucopolysaccharidosis type VI, or Maroteaux-Lamy syndrome, is a rare, autosomal recessive genetic disease, mainly affecting the pediatric age group. The disease is due to pathogenic variants of the ARSB gene, coding for the lysosomal hydrolase N-acetylgalactosamine 4-sulfatase (arylsulfatase B, ASB). The enzyme deficit causes a pathological accumulation of the undegraded glycosaminoglycans dermatan-sulphate and chondroitin-sulphate, natural substrates of ASB activity. Intracellular and extracellular deposits progressively take to a pathological scenario, often severe, involving most organ-systems and generally starting from the osteoarticular apparatus. Neurocognitive and behavioral abilities, commonly described as maintained, have been actually investigated by few studies. The disease, first described in 1963, has a reported prevalence between 0.36 and 1.3 per 100,000 live births across the continents. With this paper, we wish to contribute an updated overview of the disease from the clinical, diagnostic, and therapeutic sides. The numerous in vitro and in vivo preclinical studies conducted in the last 10-15 years to dissect the disease pathogenesis, the efficacy of the available therapeutic treatment (enzyme replacement therapy), as well as new therapies under study are here described. This review also highlights the need to identify new disease biomarkers, potentially speeding up the diagnostic process and the monitoring of therapeutic efficacy.

Glaucoma Syndromes: Insights into Glaucoma Genetics and Pathogenesis from Monogenic Syndromic Disorders

Monogenic syndromic disorders frequently feature ocular manifestations, one of which is glaucoma. In many cases, glaucoma in children may go undetected, especially in those that have other severe systemic conditions that affect other parts of the eye and the body. Similarly, glaucoma may be the first presenting sign of a systemic syndrome. Awareness of syndromes associated with glaucoma is thus critical both for medical geneticists and ophthalmologists. In this review, we highlight six categories of disorders that feature glaucoma and other ocular or systemic manifestations: anterior segment dysgenesis syndromes, aniridia, metabolic disorders, collagen/vascular disorders, immunogenetic disorders, and nanophthalmos. The genetics, ocular and systemic features, and current and future treatment strategies are discussed. Findings from rare diseases also uncover important genes and pathways that may be involved in more common forms of glaucoma, and potential novel therapeutic strategies to target these pathways.

Expanding the phenotype of mucopolysaccharidosis type II retinopathy

Purpose: To report novel retinal findings in two male patients with mucopolysaccharidosis type II (Hunter syndrome) receiving long-term human recombinant idursulfase enzyme replacement therapy.Method: Two males aged 19 and 26 years who had received enzyme replacement therapy for 12 and 13 years, respectively, with good compliance and no infusion-related reactions, were examined clinically and underwent optical coherence tomographic scanning of the retina and electroretinography testing.Results: Case 1 had visual acuity 20/32 in each eye and case 2 had visual acuity 20/25 in each eye. Both patients had clinically unremarkable anterior segment and fundus examinations. Ocular coherence tomography imaging in both patients showed thickening of the external limiting membrane with hyperreflective material in at least one eye each. One patient had bilateral foveoschisis and the other had mild foveal hypoplasia. Electroretinography showed a negative response in the patient with foveoschisis and reduced amplitudes in the patient with foveal hypoplasia.Conclusions: These two patients with Hunter syndrome receiving idursulfase treatment both have subfoveal deposition of hyperreflective material in the external limiting membrane despite good compliance and tolerance of the standard dose of enzyme therapy for this disorder. One patient has developed foveoschisis and negative electroretinogram suggesting abnormality of inner retinal function. Further studies are needed to determine the nature of the hyperreflective material, as well as the effect of systemic treatment on retinal findings in patients with mucopolysaccharidosis type II.

Gene therapy in the anterior eye segment

This review provides comprehensive information about the advances in gene therapy in the anterior segment of the eye including cornea, conjunctiva, lacrimal gland, and trabecular meshwork. We discuss gene delivery systems including viral and non-viral vectors as well as gene editing techniques, mainly CRISPR-Cas9, and epigenetic treatments including antisense and siRNA therapeutics. We also provide a detailed analysis of various anterior segment diseases where gene therapy has been tested with corresponding outcomes. Disease conditions include corneal and conjunctival fibrosis and scarring, corneal epithelial wound healing, corneal graft survival, corneal neovascularization, genetic corneal dystrophies, herpetic keratitis, glaucoma, dry eye disease, and other ocular surface diseases. Although most of the analyzed results on the use and validity of gene therapy at the ocular surface have been obtained in vitro or using animal models, we also discuss the available human studies. Gene therapy approaches are currently considered very promising as emerging future treatments of various diseases, and this field is rapidly expanding.

Macular Changes in a Mucopolysaccharidosis Type I Patient with Earlier Systemic Therapies

Purpose

To describe retinal findings in a patient with mucopolysaccharidosis type I (MPS I) that underwent an early treatment with hematopoietic stem cell transplantation (HSCT) and enzyme replacement therapy (ERT). Case Report. We describe a case of a 12-year-old female with a biochemical and genetic diagnosis of MPS I. She underwent HSCT and ERT on the first year of life. The visual acuity was 5/10 in both eyes and she had bilateral grade 2 corneal haze. Spectral domain optical coherence tomography (SD-OCT) revealed thickening of the external limiting membrane (ELM) at the fovea. In the parafoveal and perifoveal regions, SD-OCT displayed a loss of the interdigitation, ellipsoid, and myoid zones and of the ELM accompanied by progressive thinning of the outer nuclear layer. Fundus infrared imaging revealed a hyperreflective ring centred on the fovea and hyporeflective areas in temporal parafoveal regions in both eyes. En face OCT imaging revealed two hyperreflective rings on the outer retinal level.

Conclusion

This patient developed macular changes with foveal deposition of hyperreflective material and parafoveal thinning, despite early systemic treatment. Systemic therapies can provide an increase in life expectancy and stabilize visual acuity and corneal clouding, although their effect on retinal degeneration is unknown.

Systemic diseases and the cornea

There is a number of systemic diseases affecting the cornea. These include endocrine disorders (diabetes, Graves' disease, Addison's disease, hyperparathyroidism), infections with viruses (SARS-CoV-2, herpes simplex, varicella zoster, HTLV-1, Epstein-Barr virus) and bacteria (tuberculosis, syphilis and Pseudomonas aeruginosa), autoimmune and inflammatory diseases (rheumatoid arthritis, Sjögren's syndrome, lupus erythematosus, gout, atopic and vernal keratoconjunctivitis, multiple sclerosis, granulomatosis with polyangiitis, sarcoidosis, Cogan's syndrome, immunobullous diseases), corneal deposit disorders (Wilson's disease, cystinosis, Fabry disease, Meretoja's syndrome, mucopolysaccharidosis, hyperlipoproteinemia), and genetic disorders (aniridia, Ehlers-Danlos syndromes, Marfan syndrome). Corneal manifestations often provide an insight to underlying systemic diseases and can act as the first indicator of an undiagnosed systemic condition. Routine eye exams can bring attention to potentially life-threatening illnesses. In this review, we provide a fairly detailed overview of the pathologic changes in the cornea described in various systemic diseases and also discuss underlying molecular mechanisms, as well as current and emerging treatments.

Mucopolysaccharidosis Type I: A Review of the Natural History and Molecular Pathology

Mucopolysaccharidosis type I (MPS I) is a rare autosomal recessive inherited disease, caused by deficiency of the enzyme α-L-iduronidase, resulting in accumulation of the glycosaminoglycans (GAGs) dermatan and heparan sulfate in organs and tissues. If untreated, patients with the severe phenotype die within the first decade of life. Early diagnosis is crucial to prevent the development of fatal disease manifestations, prominently cardiac and respiratory disease, as well as cognitive impairment. However, the initial symptoms are nonspecific and impede early diagnosis. This review discusses common phenotypic manifestations in the order in which they develop. Similarities and differences in the three animal models for MPS I are highlighted. Earliest symptoms, which present during the first 6 months of life, include hernias, coarse facial features, recurrent rhinitis and/or upper airway obstructions in the absence of infection, and thoracolumbar kyphosis. During the next 6 months, loss of hearing, corneal clouding, and further musculoskeletal dysplasias develop. Finally, late manifestations including lower airway obstructions and cognitive decline emerge. Cardiac symptoms are common in MPS I and can develop in infancy. The underlying pathogenesis is in the intra- and extracellular accumulation of partially degraded GAGs and infiltration of cells with enlarged lysosomes causing tissue expansion and bone deformities. These interfere with the proper arrangement of collagen fibrils, disrupt nerve fibers, and cause devastating secondary pathophysiological cascades including inflammation, oxidative stress, and other disruptions to intracellular and extracellular homeostasis. A greater understanding of the natural history of MPS I will allow early diagnosis and timely management of the disease facilitating better treatment outcomes.

Odiparcil, a potential glycosaminoglycans clearance therapy in mucopolysaccharidosis VI-Evidence from in vitro and in vivo models

Mucopolysaccharidoses are a class of lysosomal storage diseases, characterized by enzymatic deficiency in the degradation of specific glycosaminoglycans (GAG). Pathological accumulation of excess GAG leads to multiple clinical symptoms with systemic character, most severely affecting bones, muscles and connective tissues. Current therapies include periodic intravenous infusion of supplementary recombinant enzyme (Enzyme Replacement Therapy–ERT) or bone marrow transplantation. However, ERT has limited efficacy due to poor penetration in some organs and tissues. Here, we investigated the potential of the β-D-xyloside derivative odiparcil as an oral GAG clearance therapy for Maroteaux–Lamy syndrome (Mucopolysaccharidosis type VI, MPS VI). In vitro, in bovine aortic endothelial cells, odiparcil stimulated the secretion of sulphated GAG into culture media, mainly of chondroitin sulphate (CS) /dermatan sulphate (DS) type. Efficacy of odiparcil in reducing intracellular GAG content was investigated in skin fibroblasts from MPS VI patients where odiparcil was shown to reduce efficiently the accumulation of intracellular CS with an EC₅₀ in the range of 1 μM. In vivo, in wild type rats, after oral administrations, odiparcil was well distributed, achieving μM concentrations in MPS VI disease-relevant tissues and organs (bone, cartilage, heart and cornea). In MPS VI Arylsulphatase B deficient mice (Arsb^-), after chronic oral administration, odiparcil consistently stimulated the urinary excretion of sulphated GAG throughout the treatment period and significantly reduced tissue GAG accumulation in liver and kidney. Furthermore, odiparcil diminished the pathological cartilage thickening observed in trachea and femoral growth plates of MPS VI mice. The therapeutic efficacy of odiparcil was similar in models of early (treatment starting in juvenile, 4 weeks old mice) or established disease (treatment starting in adult, 3 months old mice). Our data demonstrate that odiparcil effectively diverts the synthesis of cellular glycosaminoglycans into secreted soluble species and this effect can be used for reducing cellular and tissue GAG accumulation in MPS VI models. Therefore, our data reveal the potential of odiparcil as an oral GAG clearance therapy for MPS VI patients.

Whole genome sequencing for mutation discovery in a single case of lysosomal storage disease (MPS type 1) in the dog

Mucopolysaccharidosis (MPS) is a metabolic storage disorder caused by the deficiency of any lysosomal enzyme required for the breakdown of glycosaminoglycans. A 15-month-old Boston Terrier presented with clinical signs consistent with lysosomal storage disease including corneal opacities, multifocal central nervous system disease and progressively worsening clinical course. Diagnosis was confirmed at necropsy based on histopathologic evaluation of multiple organs demonstrating accumulation of mucopolysaccharides. Whole genome sequencing was used to uncover a frame-shift insertion affecting the alpha-L-iduronidase (IDUA) gene (c.19_20insCGGCCCCC), a mutation confirmed in another Boston Terrier presented 2 years later with a similar clinical picture. Both dogs were homozygous for the IDUA mutation and shared coat colors not recognized as normal for the breed by the American Kennel Club. In contrast, the mutation was not detected in 120 unrelated Boston Terriers as well as 202 dogs from other breeds. Recent inbreeding to select for recessive and unusual coat colors may have concentrated this relatively rare allele in the breed. The identification of the variant enables ante-mortem diagnosis of similar cases and selective breeding to avoid the spread of this disease in the breed. Boston Terriers carrying this variant represent a promising model for MPS I with neurological abnormalities in humans.

Intrastromal Gene Therapy Prevents and Reverses Advanced Corneal Clouding in a Canine Model of Mucopolysaccharidosis I

Mucopolysaccharidosis type I (MPS I) is an autosomal recessive lysosomal storage disease characterized by severe phenotypes, including corneal clouding. MPS I is caused by mutations in alpha-l-iduronidase (IDUA), a ubiquitous enzyme that catalyzes the hydrolysis of glycosaminoglycans. Currently, no treatment exists to address MPS I corneal clouding other than corneal transplantation, which is complicated by a high risk for rejection. Investigation of an adeno-associated virus (AAV) IDUA gene addition strategy targeting the corneal stroma addresses this deficiency. In MPS I canines with early or advanced corneal disease, a single intrastromal AAV8G9-IDUA injection was well tolerated at all administered doses. The eyes with advanced disease demonstrated resolution of corneal clouding as early as 1 week post-injection, followed by sustained corneal transparency until the experimental endpoint of 25 weeks. AAV8G9-IDUA injection in the MPS I canine eye with early corneal disease prevented the development of advanced corneal changes while restoring clarity. Biodistribution studies demonstrated vector genomes in ocular compartments other than the cornea and in some systemic organs; however, a capsid antibody response was detected in only the highest dosed subject. Collectively, the results suggest that intrastromal AAV8G9-IDUA therapy prevents and reverses visual impairment associated with MPS I corneal clouding.

Anterior Chamber Angles in Different Types of Mucopolysaccharidoses

PURPOSE

To evaluate the anterior chamber angle status and estimate the intraocular pressure (IOP) in patients with mucopolysaccharidoses (MPSs) type I, II, IV, and VI.

DESIGN

Prospective cross-sectional study.

METHODS

This study enrolled 27 consecutive MPS patients (8 patients with MPS I, 4 patients with MPS II, 9 patients with MPS IV, and 6 patients with MPS VI) and 20 normal control subjects. Anterior chamber angle status was evaluated by swept-source optical coherence tomography and IOP was estimated by the new-generation tonometer Corvis ST.

RESULTS

Twelve eyes (6 patients) of 15 eyes (8 patients) with MPS I had narrow angles or peripheral iridocorneal touches together with elevated IOP (80%). Six eyes (3 patients) of 8 eyes (4 patients) with MPS II had plateau iris configuration, but all 8 eyes had normal IOP. All 18 eyes (9 patients) with MPS IV had normal angle structures, but 8 eyes (4 patients) had elevated IOP (44.4%). Nine eyes (5 patients) of 11 eyes (6 patients) with MPS VI had shallow but not closed angles (81.8%). Among these 9 eyes, 5 eyes had elevated IOP, and 4 of these 5 eyes had IOP >30 mm Hg. The trabecular iris angles of MPS types I, II, and VI were smaller than those of MPS type IV and of the control subjects. The angle recess areas of MPS types I and VI were smaller than those of MPS type IV and of the control subjects.

CONCLUSIONS

MPS type I patients are prone to have glaucoma with narrow or closed angles; MPS type II patients tend to have plateau iris; MPS type IV patients are vulnerable to open-angle glaucoma; MPS type VI patients have narrow angles not as close as those of MPS type I. MPS types I, IV, and VI had higher IOP estimates than the control subjects, but only MPS I and IV had higher corrected IOP estimates than the control subjects. The ordinary IOP estimates in MPS VI patients may be falsely high because of clouded corneas and increased corneal rigidity. Swept-source optical coherence tomography helps ophthalmologist investigate the angle structure and the pathophysiology of glaucoma caused by MPS.

Mucopolysaccharidosis Type I

Mucopolysaccharidosis type I (MPS I) is caused by the deficiency of α-l-iduronidase, leading to the storage of dermatan and heparan sulfate. There is a broad phenotypical spectrum with the presence or absence of neurological impairment. The classical form is known as Hurler syndrome, the intermediate form as Hurler-Scheie, and the most attenuated form is known as Scheie syndrome. Phenotype seems to be largely influenced by genotype. Patients usually develop several somatic symptoms such as abdominal hernias, extensive dermal melanocytosis, thoracolumbar kyphosis odontoid dysplasia, arthropathy, coxa valga and genu valgum, coarse facial features, respiratory and cardiac impairment. The diagnosis is based on the quantification of α-l-iduronidase coupled with glycosaminoglycan analysis and gene sequencing. Guidelines for treatment recommend hematopoietic stem cell transplantation for young Hurler patients (usually at less than 30 months of age). Intravenous enzyme replacement is approved and is the standard of care for attenuated-Hurler-Scheie and Scheie-forms (without cognitive impairment) and for the late-diagnosed severe-Hurler-cases. Intrathecal enzyme replacement therapy is under evaluation, but it seems to be safe and effective. Other therapeutic approaches such as gene therapy, gene editing, stop codon read through, and therapy with small molecules are under development. Newborn screening is now allowing the early identification of MPS I patients, who can then be treated within their first days of life, potentially leading to a dramatic change in the disease's progression. Supportive care is very important to improve quality of life and might include several surgeries throughout the life course.

Progressive eye pathology in mucopolysaccharidosis type I mice and effects of enzyme replacement therapy

BACKGROUND

Mucopolysaccharidosis type I (MPS I) is a lysosomal storage disorder caused by α-L-iduronidase deficiency, resulting in accumulation of glycosaminoglycans (GAG). Ophthalmological manifestations are common in MPS I patients and often lead to visual impairment. Accumulation of GAG in corneal or retinal tissues reduces vision causing corneal opacity and neurosensory complications. One available treatment for MPS I patients is enzyme replacement therapy (ERT), but the results of such treatment on eye disease are still debatable. Therefore, we aimed to determine the progression of ocular manifestations as well as the effectiveness of intravenous ERT in MPS I.

METHODS

Corneal and retinal analyses were perform in eyes from 2- to 8-month normal and MPS I mice. Some MPS I mice received ERT (1.2 mg/kg of laronidase) every 2 weeks from 6 to 8 months and histological findings were compared with controls. Additionally, cornea from two MPS I patients under ERT were evaluated.

RESULTS

Mouse corneal tissues had GAG accumulation early in life. In the retina, we found a progressive loss of photoreceptor cells, starting at 6 months. ERT did not improve or stabilize the histological abnormalities. MPS I patients, despite being on ERT for over a decade, presented GAG accumulation in the cornea, corneal thickening, visual loss and needed corneal transplantation.

CONCLUSION

We provide data on the time course of ocular alteration in MPS I mice. Our results also suggest that ERT is not effective in treating the progressive ocular manifestations in MPS I mice and fails to prevent corneal abnormalities in patients.

Ophthalmological Findings in Mucopolysaccharidoses

The mucopolysaccharidoses (MPS) are a heterogenous group of lysosomal storage disorders caused by the accumulation of glycosaminoglycans (GAGs). The accrual of these compounds results in phenotypically varied syndromes that produce multi-organ impairment with widespread systemic effects. The low incidence of MPS (approximately 1/25,000 live births) in conjunction with the high childhood mortality rate had limited the availability of research into certain clinical features, especially ocular manifestations. As the recent successes of hematopoietic stem cell transplantation (HSCT) and enzyme replacement therapy (ERT) have greatly increased life expectancy in these patients, they have served as a focal point for the transition of research towards improvement of quality of life. Ophthalmological findings in MPS include corneal clouding, glaucoma, optic neuropathies, and retinopathies. While corneal clouding is the most common ocular feature of MPS (especially type I, IVA, and VI), its response to HSCT and ERT is minimal. This review discusses known eye issues in the MPS subtypes, diagnosis of these ocular diseases, current clinical and surgical management, noteworthy research progress, and ultimately presents a direction for future studies.

Ophthalmologic manifestations in Taiwanese patients with mucopolysaccharidoses

Background

Mucopolysaccharidoses (MPSs) are a group of rare lysosomal storage disorders characterized by the accumulation of glycosaminoglycans in various tissues and organs. Ocular problems that affect the cornea, trabecular meshwork, sclera, retina, and optic nerve are very common in these patients. However, there was limited literature focusing on comprehensive ocular findings in different types of MPS.

Methods

We retrospectively reviewed the clinical ophthalmologic features and electrodiagnostic results of 50 Taiwanese patients with a diagnosis of MPS (34 males and 16 females; age range, 1.1–34.9 years; nine with MPS I, 17 with MPS II, 17 with MPS IV, and seven with MPS VI).

Results

Among 44 patients with available data for visual acuity, 15 patients (34%) had a visual acuity of less than 0.5 (6/12) equivalent in their better eye, including 71% of those with MPS VI, 38% with MPS IV, 29% with MPS I, and 14% with MPS II. Severe corneal opacities existed in 57% of MPS VI patients and 11% of MPS I patients, compared with none for MPS II and MPS IV patients. Among 80 eyes with available data of refraction, 11 eyes (14%) had myopia (≦−0.50 D), 55 eyes (69%) had hyperopia (≧0.50 D), and 55 eyes (69%) had high astigmatism (≧1.50 D). Ocular hypertension was found in 45% (28/62) of eyes. There were 16% (14/90), 11% (10/90), 13% (12/90), 31% (27/86), and 79% (30/38) of MPS eyes with lens opacities, optic disc swelling, optic disc cupped, retinopathy, and visual pathway dysfunction, respectively. Intraocular pressure was positively correlated with the severity of corneal opacity (p < 0.01).

Conclusions

Ocular complications with significant reduction in visual acuity are common in MPS patients. Diagnostic problems may arise in these patients with severe corneal opacification, especially for those with MPS VI and MPS I.

Ocular features in mucopolysaccharidosis: diagnosis and treatment

Mucopolysaccharidoses (MPS) are a group of rare lysosomal storage disorders characterized by the accumulation of glycosaminoglycans (GAGs) in different parts of the eye. Ocular problems are very common in MPS children, and the cornea, sclera, trabecular meshwork, retina, and optic nerve may all be involved. Early diagnosis is very important to preserve the visual function, and the diagnosis requires experience and different evaluations. Follow-up is mandatory to allow a correct pathway to consequent therapy. This article aims to provide a review of ocular alterations and treatment options in MPS. The ophthalmologist is sometimes the first physician who can suspect a metabolic disease and can help to make the correct diagnosis. It is important to stimulate awareness of MPS among ophthalmologists.

Children with mucopolysaccharidosis risk progressive visual dysfunction despite haematopoietic stem cell transplants

AIM

This prospective study assessed the long-term ocular and visual outcomes of children with mucopolysaccharidoses type I Hurler syndrome (MPS IH) who were treated with haematopoietic stem cell transplants (HSCT).

METHODS

Clinical ophthalmological assessments were performed on eight patients at the St Erik Eye Hospital, Huddinge, Stockholm, Sweden, from 2001-2018: The median age at diagnosis and HSCT were 12.2 (range 5.0-16.4) and 16.7 (8.0-20.4) months. The last eye examination was at a median of 13.4 (6.3-19.0) years and follow-up lasted a median of 12.0 (5.0-17.4) years.

RESULTS

Poor visual acuity, poor night vision and, or, photophobia were reported by six children. The best corrected visual acuity at the last visit was a median of 0.4 and 0.5 in the right and left eye and had declined significantly in two patients. Corneal opacities had increased despite HSCT in five patients. High hyperopia, at a median of +6 Dioptres, occurred in all patients and stiff corneas in all four patients that were measured. The patients' corrected intraocular pressures were normal. Retinal degeneration was identified in two patients.

CONCLUSION

Despite HSCT, the long-term follow-up of patients with MPS IH showed reduced visual acuity due to corneal opacities or retinal degeneration.

Mucopolysaccharidosis Type I and Bilateral Optic Disc Edema

Mucopolysaccharidosis type I (MPS I or Hurler syndrome) is a multisystem genetic disorder caused by α-L-iduronidase (IDUA) deficiency, which leads to widespread accumulation of glycosaminoglycans triggering tissue damage and organ dysfunction. A variety of ocular manifestations have been described in Hurler Syndrome. We present the case of an 11-year-old boy with Hurler Syndrome and optic disc edema related to ocular glycosaminoglycan deposition. This report advances the idea that the optic nerve swelling seen in MPS I is likely influenced as much by biomechanical changes at the optic nerve head as by increased intracranial pressure.

Targeting Root Cause by Systemic scAAV9-hIDS Gene Delivery: Functional Correction and Reversal of Severe MPS II in Mice

No treatment is available to address the neurological need and reversibility of MPS II. We developed a scAAV9-hIDS vector to deliver the human iduronate-2-sulfatase gene and test it in mouse model. We treated MPS II mice at different disease stages with an intravenous injection of scAAV9-mCMV-hIDS at different doses. The treatments led to rapid and persistent restoration of IDS activity and the reduction of glycosaminoglycans (GAG) throughout the CNS and somatic tissues in all cohorts. Importantly, the vector treatment at up to age 6 months improved behavior performance in the Morris water maze and normalized the survival. Notably, vector treatment at age 9 months also resulted in persistent rIDS expression and GAG clearance in MPS II mice, and the majority of these animals survived within the normal range of lifespan. Notably, the vector delivery did not result in any observable adverse events or detectable systemic toxicity in any treated animal groups. We believe that we have developed a safe and effective gene therapy for treating MPS II, which led to recent IND approval for a phase 1/2 clinical trial in MPS II patients, further supporting the extended potential of the demonstrated systemic rAAV9 gene delivery platform for broad disease targets.

Variability in the ocular phenotype in mucopolysaccharidosis

PURPOSE

Mucopolysaccharidoses (MPSs) are a heterogeneous group of lysosomal storage disorders. Ocular complications (such as corneal clouding, retinopathy and optic neuropathy) are common. Notably, there is a paucity of data on the effect of genotype and systemic treatments (enzyme replacement therapy or haematopoietic stem cell transplantation) on the ocular phenotype in MPS. We prospectively studied the ocular features of patients with MPSI (Hurler/Hurler-Scheie/Scheie), MPSIV (Morquio) and MPSVI (Maroteaux-Lamy), to evaluate the effect of different therapeutic interventions and to correlate the findings with genetic and biomarker data.

METHODS

Prospective observational cohort study. Study participants underwent detailed ocular examination including visual acuity; assessment of corneal clouding (Iris camera Corneal Opacification Measure score and Pentacam densitometry) and retinal and optic nerve imaging (optical coherence tomography and wide-field fundus imaging). Data on genotype, biomarkers and delivered therapies (type and length of treatment) were also collected for each patient where available.

RESULTS

Overall, 21 patients with MPSI, 4 patients with MPSIV and 3 patients with MPSVI were recruited. Corneal clouding scores were higher in MPSI compared with MPSIV and MPSVI. Retinopathy was evident in patients with MPSI only. Association was observed between corneal clouding and biomarkers in MPSI, MPSIV and MPSVI. However, no clear association was seen between genotype or treatment type and ocular phenotype.

CONCLUSIONS

The ocular phenotype in MPS is variable, with corneal clouding occurring in MPSI, MPSIV and MPSVI, and retinopathy in MPSI only. There was an association between corneal clouding and efficacy of systemic treatment as measured by biomarkers.

Bull's eye maculopathy and subfoveal deposition in two mucopolysaccharidosis type I patients on long-term enzyme replacement therapy

Purpose

To report retinal findings in two patients with mucopolysaccharidosis type I (MPS I) receiving human recombinant alpha-l-iduronidase (Laronidase) as enzyme replacement therapy.

Observations

Patient 1 had visual acuity 20/20 right eye, 20/25 left eye and unremarkable anterior segment and retinal examination. Optical coherence tomography (OCT) scanning demonstrated parafoveal thinning and subfoveal hyperreflectant material. Patient 2 had visual acuity 20/20 both eyes, with dense nuclear cataract both eyes. Retinal examination demonstrated bull's eye maculopathy both eyes. OCT scanning confirmed parafoveal atrophy and demonstrated similar appearing subfoveal hyperreflectant material, more prominent than in case 1.

Conclusions and importance

These two patients with MPS I receiving Laronidase treatment have developed bull's eye maculopathy changes and subfoveal deposition of hyperreflectant material despite excellent compliance and good tolerance of the standard dose of enzyme therapy for this disorder. Further studies are required to determine the nature of the material, the incidence and the effect of enzyme replacement therapy on these findings in patients with MPS I.

A Case of a Bilateral Cicatricial Upper Eyelid Entropion After Hematopoietic Stem Cell Transplantation in Mucopolysaccharidosis Type I

Minor eyelid abnormalities are commonly encountered in mucopolysaccharidosis, but only rarely leading to a clinically relevant situation. The authors report a clinical case of severe bilateral cicatricial entropion of the upper eyelids, leading to recurrent conjunctival infections, corneal erosion, persistent epiphora, and a major decline in life quality in a 7-year-old boy with mucopolysaccharidosis type I who underwent hematopoietic stem cell transplantation at 1.6 years old. A bilateral anterior lamellar repositioning including eyelid split and cryoepilation was performed to correct bilateral upper eyelid entropium and trichiasis. Three months after the surgical intervention, the patient showed a persistent regular eyelid position with only mild recurrent right-sided lateral upper eyelid entropion. A significant reduction in conjunctival infections and epiphora with complete discontinuation of topical therapy was achieved. Although mucopolysaccaridosis is associated with eyelid abnormalities, the authors conclude that the described case is most likely due to chronic graft versus host disease.

Influence of Corneal Opacity on Intraocular Pressure Assessment in Patients with Lysosomal Storage Diseases

AIMS

To investigate an influence of mucopolysaccharidosis (MPS)- and Morbus Fabry-associated corneal opacities on intraocular pressure (IOP) measurements and to evaluate the concordance of the different tonometry methods.

METHODS

25 MPS patients with or without corneal clouding, 25 Fabry patients with cornea verticillata ≥ grade 2 and 25 healthy age matched controls were prospectively included into this study. Outcome measures: Goldmann applanation tonometry (GAT); palpatory assessment of IOP; Goldmann-correlated intraocular pressure (IOPg), corneal-compensated intraocular pressure (IOPcc), corneal resistance factor (CRF) and corneal hysteresis (CH) assessed by Ocular Response Analyzer (ORA); central corneal thickness (CCT) and density assessed with Pentacam. Statistical analysis was performed using linear mixed effect models and Spearman correlation coefficients. The concordance between tonometry methods was assessed using Bland-Altman analysis.

RESULTS

There was no relevant difference between study groups regarding median GAT, IOPg, IOPcc and CCT measurements. The limits of agreement between GAT and IOPcc/IOPg/palpatory IOP in MPS were: [-11.7 to 12.1mmHg], [-8.6 to 15.5 mmHg] and [- 5.4 to 10.1 mmHg] respectively. Limits of agreement were less wide in healthy subjects and Fabry patients. Palpatory IOP was higher in MPS than in healthy controls and Fabry patients. Corneal opacity correlated more strongly with GAT, IOPg, CH, CRF, CCT and corneal density in MPS (r = 0.4, 0.5, 0.5, 0.7, 0.6, 0.6 respectively) than in Fabry patients (r = 0.3, 0.2, -0.03, 0.1, 0.3, -0.2 respectively). In contrast, IOPcc revealed less correlation with corneal opacity than GAT in MPS (r = 0.2 vs. 0.4).

CONCLUSIONS

ORA and GAT render less comparable IOP-values in patients suffering from MPS-associated corneal opacity in comparison to Fabry and healthy controls. The IOP seems to be overestimated in opaque MPS-affected corneas. GAT, IOPg and biomechanical parameters of the cornea correlate more strongly with the corneal clouding than IOPcc in MPS patients.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01695161.

Atypical Presentation of Acute Angle-Closure Glaucoma in Maroteaux-Lamy Mucopolysaccharidosis with Patent Prophylactic Laser Peripheral Iridotomy: A Case Report

INTRODUCTION

Maroteaux-Lamy syndrome (MLS) is a rare progressive condition characterized by inflammation and scarring of multiple organs. Ocular complications caused by anterior segment abnormalities commonly cause visual impairment in MLS. Angle-closure glaucoma is one such complication, but there are limited data on presentation, workup, and management of this condition.

CASE PRESENTATION

This case report describes an atypical presentation of acute angle-closure glaucoma in a patient with MLS despite a prior prophylactic laser peripheral iridotomy-which would typically prevent an acute angle-closure attack-that was patent and intact at the time of angle closure.

DISCUSSION

Because of severe congenital anterior segment crowding, high axial hyperopia, and constant accommodative demand in patients with MLS, we recommend performing two prophylactic laser peripheral iridotomies simultaneously in the same eye instead of one. The mechanism for this indication differs from that in patients at risk of acute angle-closure glaucoma because of lens zonulopathy alone. We hope that this case report may help prevent vision loss and optimize quality of life in patients with MLS who may be wheelchair-bound but are typically high functioning with normal intelligence.