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M. W. Seeliger, B. Wissinger, E. Zrenner, D. Nagy, M. D. Fischer; Effects of Serum Retinol-Binding Protein (sRBP) Deficiency on Development and Degeneration of the Human Retina. Invest. Ophthalmol. Vis. Sci. 2009;50(13):974.
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© ARVO (1962-2015); The Authors (2016-present)
Serum retinol-binding protein (sRBP) is the key transporter of Vitamin A to the Retina. The uptake via the retinal pigment epithelium (RPE) is mediated by the recently discovered STRA6 receptor. In 1999, we described a family with compound heterozygous mutations in the RBP4 gene encoding sRBP (OMIM 180250). Here, we present the results of a 10 year follow-up of these patients, as well as phenotypic data of a new sibling (the child of one affected female) that provide novel insights about the role of sRBP during development.
Patients underwent a basic ophthalmologic examination, visual field and colour vision tests, dark adaptometry, an electrophysiological (ERG) assessment, and fundus imaging/SLO at several time points during the past decade. A sequence analysis of the RBP4 gene was performed to confirm the heterozygosity of the new sibling.
In the two patients carrying the compound heterozygous mutations, the developmental aberrations were rather mild, but there was a clear functional deficit and signs of a retinal degeneration that appeared to be progressive. Particularly remarkable was the development of white-yellowish spots in the mid periphery reminiscent of other retinoid cycle disorders that were not present initially. In contrast, the heterozygous child had much more expressed developmental defects, most prominently a bilateral coloboma reaching from the iris until close to the optic nerve.
sRBP deficiency appears to be a moderately progressive retinal degenerative disorder that may on the basis of the functional phenotype and degenerative nature roughly be placed between fundus albipunctatus and retinitis punctata albescens. The fact that the heterozygous child carries the same mutation as its phenotypically unaffected grandmother indicates that the maternal sRBP/retinol status, rather than the individual one, is decisive for the developmental component, whereas the individual status determines the expression of the retinal degeneration.
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