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Gil Ben-Shlomo, R D. Whitley, Jackie K. Jens, Patricia I. Dickson, N M. Ellinwood; Clinical Ophthalmological Characterization of the Canine Model of Mucopolysaccharidosis Type I. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2359.
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Mucopolysaccharidosis type I (MPS I) [OMIM 607014-16] is an inborn error of metabolism characterized by lysosomal storage of the glycosaminoglycans heperan sulfate and dermatan sulfate, which accumulate as a result of the recessively inherited loss of alpha-L-iduronidase (EC 220.127.116.11) activity. Clinical signs vary depending on the degree of residual enzyme activity from most severe (Hurler Syndrome) with pronounced multisystem disease and death in the first decade, to attenuated (Scheie syndrome), which is characterized by normal lifespan, arthritides, and ophthalmic disease. Treatment in the form of bone marrow transplantation and enzyme replacement therapy (ERT) exist, but of the ophthalmic disease, and specifically the corneal disease remains among the most resistant tissues to full correction by these therapies. Recent studies with high dose ERT in the canine model have shown potential to treat corneal disease in this disorder. Further assessment of corneal directed treatments require a more thorough assessment of the clinical disease in the canine MPS I model.
Eight dogs affected with MPS I were of a mixed breed background and were homozygous for the Plott hound IDUA mutation, and were examined beginning at 8 months of age by trained veterinary ophthalmologists. Ophthalmic examination included slit-lamp biomicroscopy, fluorescein staining, rebound tonometry and indirect funduscopy.
All dogs presented with a diffuse corneal opacity and corneal neovascularization in varying degrees. Four of the dogs had central, anterior stromal and epithelial, circular, white opacities consistent with corneal dystrophy. Lenticular and posterior segment examinations were free of abnormalities. Intraocular pressures were within normal limits and no signs of discomfort were noted.
The clinical finding documented herein, serve as a baseline and will allow for clinically relevant parameters to be used to monitor in vivo, the effectiveness of therapeutic approaches to ameliorate the otherwise intractable ophthalmic symptoms of MPS I.
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