Ocular pathology of the Maroteaux-Lamy syndrome (systemic mucopolysaccharidosis type VI). Histologic and ultrastructural report of two cases

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.

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.

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.

Fundoscopic Changes in Maroteaux-Lamy Syndrome

Purpose

To describe a clinical case of mucopolysaccharidosis type VI (MPS VI), or Maroteaux-Lamy syndrome, with fundoscopic alterations that may correspond to scleral deposits of glycosaminoglycans.

Materials and Methods

Clinical case report.

Results

A 16-year-old girl with MPS VI was examined at the Ophthalmology Department for poor vision due to opacified corneas. Treatment consisted of bilateral penetrating keratoplasty. Retinographies and enhanced depth imaging optical coherence tomography (EDI-OCT) were performed after surgery, suggesting the presence of scleral glycosaminoglycan deposits. The patient evolved with stable corneal and fundoscopic findings.

Conclusions

To our knowledge, this is the first case of MPS VI described in vivo with suspected deposits of glycosaminoglycans in the sclera. Fundoscopic alterations are not usually included in the ocular pathological spectrum of MPS VI. However, with improved control of systemic comorbidities, survival rates of these patients have increased, which in turn has made it possible to observe other changes besides the ones that were classically described. Despite being particularly challenging to manage, efforts should be made to maximizing the visual acuity of these patients, in order to provide them the best possible quality of life.

Clinical and morphological features including expression of betaig-h3 and keratan sulphate proteoglycans in Maroteaux-Lamy syndrome type B and in normal cornea

AIM

To carry out a detailed morphological study of the cornea of a 16 year old female with a Maroteaux-Lamy syndrome (MLS).

METHODS

Following a penetrating keratoplasty in July 1999, ultrastructural changes in the cornea were examined using electron microscopy. Proteoglycans were visualised using cuprolinic blue dye; and betaig-h3 and keratan sulphate were detected by immunoelectron microscopy.

RESULTS

The epithelial cells were degenerate and contained apoptotic nuclei. Proteoglycans were present in epithelial cells, intercellular spaces, and in swollen desmosomes. An abnormally large quantity of proteoglycans was present throughout the stroma. Keratocytes throughout the stroma had no cell organelles, were vacuolated, and contained a large quantity of abnormal proteoglycans. Labelling for betaig-h3 was intense around electron lucent spaces in stroma. No labelling was seen in keratocytes or endothelial cells. In normal cornea, keratan sulphate labelling was regular throughout the stroma. In MLS VI type B cornea, keratan sulphate labelling was weak in the anterior stroma but very intense in the posterior stroma and in keratocyte lysosomes and vacuoles.

CONCLUSION

A deficiency of aryl sulfatase B results in the deposition of keratan sulphate proteoglycan and other proteoglycans in lysosomes, causing the death of keratocytes and an abnormal build-up of proteoglycans in the stroma. This might be responsible for the lateral aggregation of collagen fibrils and impaired fibrillogenesis in MLS VI. Degenerate swollen keratocytes, together with gross changes in epithelial, stromal, and endothelial cells, would be expected to increase light scattering significantly in these corneas.

Findings in the anterior segment on ultrasound biomicroscopy in Maroteaux-Lamy syndrome

PURPOSE

Maroteaux-Lamy syndrome is one of the mucopolysaccharidoses caused by enzyme deficiency (arylsulfatase B) that leads to incomplete degradation and storage of dermatan sulfate. We report a case of mucopolysaccharidosis type VI (MPS VI; Maroteaux-Lamy syndrome) with corneal involvement and introduce ultrasound biomicroscopy (UBM) as an examination with which to follow disease progression in relation to deposition in cornea, angle, and iris.

METHODS

We describe a 11-year-old boy with a clinical and laboratorial diagnosis of MPS VI who developed increasing bilateral corneal opacification and decreased visual acuity. He underwent two seriate UBM (50-MHz transducer) evaluations.

RESULTS

UBM examination showed diffuse and homogeneous stromal hyper-reflective deposit in both eyes and an increase in peripheral corneal thickness throughout time.

CONCLUSION

High-frequency ultrasound documentation of corneal deposit and anterior segment involvement in a patient with Maroteaux-Lamy syndrome is unique, and follow-up revealed thickening of the corneal periphery, which may be related to the progression of the disease (continuous mucopolysaccharide deposits in corneal stroma). UBM was used to locate and document the deposit, as well as to accompany the deposit's evolution, characterizing corneal changes and angle structure involvement.

Pathological characteristics of mucopolysaccharidosis VI in the rat

The histological and electron microscopical characteristics of the pathology of rats with arylsulphatase B-deficient mucopolysaccharidosis (mucopolysaccharidosis VI; MPS VI) were investigated. In affected animals, intracytoplasmic vacuoles were prominent in chondrocytes, the macrophage system, cardiac valve fibroblasts, cornea, connective tissues, vascular smooth muscle cells and uterine stromal cells. Tissues containing glucosaminoglycans stored in lysosomes were positive to Mowry's colloidal iron and alcian blue stains. By electron microscopy, the lysosomes were seen to be distended by electron lucent or fine fibrillary storage material, and lysosomal storage was also detected in the endothelial cells of the arteries and cornea. In the central and peripheral nervous system abnormalities were restricted to the connective tissue. Lesions in the affected rats resembled those described in human and feline mucopolysaccharidosis VI. These results indicate that MPS VI of the rat may be a useful animal model for human MPS VI (Maroteaux-Lamy syndrome).

The eye and liver disorders

There are ocular changes associated with a wide spectrum of congenital, familial and acquired liver diseases and disorders. The early identification of ocular changes may aid diagnosis of the underlying liver condition. This is particularly important in conditions where there are effective treatments which can arrest hepatic damage. It is also of considerable value in patients who have untreatable disorders because identification of the correct diagnosis may offer prognostic information and spare the patient unnecessary invasive investigation. This article discusses the ocular findings in selected liver disease and reviews the current literature on the subject. The principles of investigation and diagnosis and treatment are described. Data on the incidence and prevalence of ocular involvement in liver conditions are included where such figures are available. The potential transmission of viral hepatitis following corneal grafting is discussed.

Optic nerve head swelling and optic atrophy in the systemic mucopolysaccharidoses

The ocular findings in 108 patients representative of all types of mucopolysaccharidoses (MPS) were reviewed. Attention was focused on optic nerve head appearance. Optic nerve head swelling was observed in 8/14 eyes of MPS 1-Hurler (MPS 1-H); 9/21 MPS 1-Hurler-Scheie (MPS 1-H-S); 0/4 MPS I-S; 13/66 MPS II; 1/22 MPS III; 0/58 MPS IV; 5/12 MPS VI; and 2/2 MPS VII eyes. In three patients, optic nerve head swelling was present in one eye and optic atrophy in the fellow eye; in four patients, optic atrophy followed disc elevation; three patients presented with bilateral optic atrophy. It was concluded that optic nerve head swelling precedes the development of optic atrophy in the systemic MPS.

Ocular histopathology and ultrastructure of Morquio syndrome (systemic mucopolysaccharidosis IV A)

Morquio syndrome (mucopolysaccharidosis IV) is a hereditary lysosomal storage disease characterized by dwarfism, spondyloepiphyseal and dental abnormalities, corneal opacification, and normal intelligence. We report the light and electron microscopic features of two patients with mucopolysaccharidosis type IV A (MPS IV A). Variable degrees of mucopolysaccharide deposition were seen in tissue surveyed by light microscopy. Transmission electron microscopy demonstrated fibrillogranular and multimembranous membrane-bound inclusions distributed primarily in the cornea and trabecular meshwork, to a milder degree in the conjunctiva and sclera, and rarely in the retinal pigment epithelium. Our findings indicate that the accumulation of mucopolysaccharide in MPS IV A occurs primarily in the structures of the anterior segment.

Scheie's syndrome. An ultrastructural analysis of the cornea

The histopathology of a corneal graft specimen obtained from a patient with Scheie's syndrome (systemic mucopolysaccharidosis, type IS) is described with particular emphasis on the ultrastructural findings. Numerous vacuoles containing fibrillogranular material were found in the corneal epithelial cells, the keratocytes, and the endothelial cells. The basement membrane of the epithelium contained frequent breaks and peg-like undulations, and Bowman's layer was markedly attenuated. Fibrous long-spacing (FLS) collagen featured prominently in the stroma. Descemet's membrane was normal. The findings of a markedly attenuated Bowman's layer and FLS collagen may be abnormalities specific to Scheie's syndrome resulting from the altered glycosaminoglycan composition of the extracellular matrix.

Glaucoma in the Maroteaux-Lamy syndrome

We report four patients who had glaucoma in association with the Maroteaux-Lamy syndrome. Two of these patients had acute angle-closure glaucoma, one had chronic angle-closure glaucoma, and one was treated for open-angle glaucoma; however, the angle structures could not be seen by gonioscopy. Standard peripheral iridectomy was inadequate for treatment of this angle-closure glaucoma because of the considerably increased thickness of the peripheral cornea that occurs in these patients. Our findings suggest that glaucoma may be more common in the Maroteaux-Lamy syndrome than has been realized and that the initial mechanism is secondary acute or chronic angle closure not related to pupillary block.

Ocular changes in the mucopolysaccharidoses after bone marrow transplantation. A preliminary report

Metabolic correction and physiologic response were evaluated after bone marrow transplantation in mucopolysaccharidosis. Eleven patients were prospectively evaluated to determine the effect of bone marrow transplantation on the progressive ocular manifestations of these disorders. Follow-up of 0.6 to 2.8 years after successful donor stem cell engraftment showed that some patients had slow clearing of the corneal clouding, reduction of intracytoplasmic inclusions in the conjunctiva, resolution of optic nerve edema, and stabilized or improved retinal function as determined by electroretinography. These preliminary results suggest that early bone marrow transplantation may alter some of the progressive ophthalmic characteristics of the mucopolysaccharidoses. Long-term follow-up is necessary to determine if these early alterations in the ocular features are predictive of a prolonged functional improvement in the visual status.

Ocular histopathology of systemic mucopolysaccharidosis, type II-A (Hunter syndrome, severe)

A case of mucopolysaccharidosis, Type II-A (Hunter syndrome, severe) is described, with emphasis on ocular ultrastructural findings. Single membrane-bound structures containing fibrillogranular and, less commonly, multi-membranous material were found in conjunctival epithelium, pericytes and fibrocytes; corneal epithelium, keratocytes, and endothelium; trabecular endothelium; iris pigmented epithelium, smooth muscle, and fibrocytes; ciliary pigmented and nonpigmented epithelium and fibrocytes; retinal pigment epithelium and ganglion cells; optic nerve astrocytes and pericytes; and sclerocytes. The most striking accumulation was in the nonpigmented ciliary epithelium. These findings are compared with those seen in MPS II-B, and in other systemic mucopolysaccharidoses. The nature and distribution of inclusions are not specific to any one disorder, but help to signal the presence of one of the storage disorders. Distension of corneal keratocytes may play a role in the corneal clouding seen in some of these disorders. The importance of tissue examination, especially conjunctival biopsy, in the diagnosis of storage disorders and in assessment of future modes of therapy for the mucopolysaccharidoses is discussed.

Genetics in pediatric ophthalmology

Genetic factors are becoming increasingly important causes of both congenital and acquired eye disease in the pediatric age group. Referral to an ophthalmologist is important both for global genetic disorders potentially affecting the eye and for eye disorders that may be diagnostic for genetic disease.

Histological and ultrastructural studies of the cornea in Maroteaux-Lamy syndrome

The author presents the histologic and electron-microscopic examination of the cornea of a patient with Maroteaux-Lamy syndrome. Histochemic examinations established the absence of keratin sulfate and heparin sulfate in the accumulated material. By means of electron microscopy three cell types have been found in the stroma which may show, besides the storage of the accumulated glycosaminoglycans, the morphologic signs of the pathologic enzyme-substrate connection. Considering the presence of the lipidlike material, the question arises whether the Maroteaux-Lamy syndrome belongs to mucolipidoses.

Ultrastructural aspects of corneal fibrous tissue in the Scheie syndrome

An ultrastructural study of the corneal fibrous tissue was performed in a case of Scheie's syndrome. Mucopolysaccharidosis deposits in keratocytes were observed as electron-clear and electron-dense inclusions. Modifications of the extracellular space included modifications of lamellar collagen organization and local hypertrophy of collagen bundles; presence of microfibrillar dense material isolating large irregular collagen fibers; and presence of fibrous long spacing type collagen fibers. The significance of these changes is discussed. This special form of collagen organization is supposed to appear in a modified microenvironment, that is the presence of an abnormal concentration of proteoglycans.

Contributions of electron microscopy to the study of corneal pathology

Most of the electron microscopic studies of pathological corneas have been done only recently. Keratoplasty has been the most important source of specimens for ultramicroscopic investigation. With the introduction of electron microscopic techniques, we have been able to confirm many light microscopic studies in pathological corneas. This contribution has been most valuable in the identification of the sites and types of pathological changes in corneal dystrophies and degenerations. This review of electron microscopic studies describes the present concepts on the nature of the histological changes in dystrophies and degenerations of the anterior and posterior corneal layers and corneal stroma. It also includes a review of some corneal inflammatory conditions as well as metabolic disorders affecting its transparency.

Ocular findings in Niemann-Pick disease

Light and electron microscopic studies of the eyes of a 3 1/2-year-old girl who died of Niemann-Pick disease disclosed accumulation of intralysosomal lipid material in all cells other than those that were pigmented. The nonpigmented layer of the ciliary process and the ganglion cells of the retina were especially involved. Electron microscopy revealed two main types of lipid cytosomes. The presumptive explanation for this finding is that the metabolism of the stored material in neurons differs from that in other cells. Topographic and structural studies of the pathologic pigment epithelium suggested that pigmented cells show storage material either when they are in intimate contact with affected cells or when the enzyme defect interferes with the catabolism of the outer segments.

Acute glaucoma in systemic mucopolysaccharidosis I-S

Two siblings, a 56-year-old white man and a 44-year-old white woman, with systemic mucopolysaccharidosis I-S (Scheie's syndrome) developed acute glaucoma successively in each eye. Their management was complicated by an inability to visualize the anterior chamber angle due to corneal clouding by acid mucopolysaccharide (AMP) deposition. The mechanism of their glaucoma resembled angle closure, which may have been related to thickening of anterior ocular structures due to abnormal AMP storage.

Corneal clouding with increased acid mucopolysaccharide accumulation in Bowman's membrane

Two infants had bilateral congenital corneal clouding and abnormal acid mucopolysaccharide accumulation in a thickened Bowman's membrane. This unusual entity was not associated with acid mucopolysaccharide deposits in the skin and visceral tissues or with increased levels of acid mucopolysaccharide in the urine. The similarity and differences have been compared to the systemic mucopolysaccharidosis and macular corneal dystrophy.