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Ocular histopathology of systemic mucopolysaccharidosis, type II-A (Hunter syndrome, severe)
Abstract:
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.
Insights
This study details ocular ultrastructural findings in a severe Hunter syndrome (Mucopolysaccharidosis Type II-A) case. Inclusions were found across various eye tissues, highlighting the need for tissue examination in diagnosing storage disorders.
Area of Science:
- Ophthalmology
- Genetics
- Cell Biology
Background:
- Mucopolysaccharidoses (MPS) are a group of genetic disorders characterized by the accumulation of glycosaminoglycans.
- Hunter syndrome (MPS II) is an X-linked recessive disorder with varying clinical severity.
- Ocular manifestations are common in MPS, but detailed ultrastructural findings are less understood.
Observation:
- A severe case of Hunter syndrome (MPS II-A) was examined for ocular ultrastructural pathology.
- Single membrane-bound inclusions, containing fibrillogranular and multi-membranous material, were identified in multiple ocular tissues.
- These inclusions were most prominent in the nonpigmented ciliary epithelium.
Findings:
- Ultrastructural inclusions were observed in conjunctival, corneal, iris, ciliary body, retinal, optic nerve, and scleral cells.
- The nature and distribution of these inclusions were compared to MPS II-B and other MPS types.
- Corneal keratocyte distension may contribute to the corneal clouding observed in some MPS disorders.
Implications:
- The presence of these inclusions is indicative of storage disorders, though not specific to a single type.
- Conjunctival biopsy is a valuable diagnostic tool for storage disorders.
- Understanding ultrastructural pathology is crucial for assessing future therapeutic strategies for mucopolysaccharidoses.