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A. Rice, S. Naylor, D. M. Spokes, S. Anand, J. L. Ball, A. J. Morrell, C. F. Inglehearn; Corneal Endothelial Status in Parents of Ched Patients With Recessive Mutations in SLC4A11. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4637.
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Congenital hereditary endothelial dystrophy (CHED) is a bilateral corneal dystrophy inherited as a dominant or recessive condition. All arCHED cases analysed to date, and all Harboyan syndrome patients (arCHED with progressive perceptive deafness), result from homozygous mutations in the sodium-borate co-transporter SLC4A11. Fuchs endothelial corneal dystrophy (FECD) is a late onset condition with remarkable phenotypic similarity to CHED, and 5% of FECD patients were found to be heterozygous for SLC4A11 mutations similar to those that cause CHED (Vithana et al 2008, HMG 17;656). This finding suggests that parents of CHED patients, themselves carriers for CHED mutations, are at risk of FECD. We therefore examined the corneal endothelia of SLC4A11 mutation carriers.
Four parents aged 37, 39, 39 and 41 years, and three siblings aged 10, 9 and 7 years, all heterozygous for the SLC4A11 G464D mutation, were recruited from two previously characterised consanguineous CHED families (Vithana et al 2006, Nat Gen 38;755). Carrier status was confirmed in genomic DNA. Each individual was assessed with OrbScan II corneal topography and specular microscopy.
Endothelial cell densities ranged from 2451 to 3593 per mm2, within the normal range and well above the level at which the cornea might be expeced to decompensate. Cell morphology appeared normal and no other endothelial abnormalities were observed in any of these patients.
Up to age 41 the corneal endothelium in heterozygous carriers of CHED-causing SLC4A11 mutations appear normal. Lack of endothelial dystrophy in these patients would call into question the findings of Vithana and colleagues. However age at onset of FECD is most commonly in the fifth decade. These patients will therefore require regular repeat examination in the future to detect any possible changes in endothelial cell status and thus confirm the involvement of heterozygous mutations in SLC4A11 as a cause of FECD.
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