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Mieke M. Bijveld, Maria M. Genderen, van, Frans C. Riemslag, Frank P. Hoeben, Arthur A. Bergen, Astrid M. Kappers, Maarten Kamermans; Genotype and Phenotype of Patients with Congenital Stationary Night Blindness (CSNB). Invest. Ophthalmol. Vis. Sci. 2011;52(14):2377.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate (1) correlations between phenotype and genotype of X linked and autosomal recessive congenital stationary night blindness (Xl-CSNB, ar-CSNB), (2) the relative frequency of the genetic causes of CSNB in a group of Dutch patients.
We approached 60 patients that were previously diagnosed with CSNB to participate in this study and to donate a blood sample. We also included 35 CSNB patients that are having their genetic mutation tested for diagnostic purposes. The phenotype included: visual acuity, refractive error, visual field, photophobia, night blindness, nystagmus, strabismus, elevation of dark adaptation curve and standard ISCEV ERG.
Comprehensive mutation screening identified gene mutations. At the time this abstract was written we found the following distribution based on family anamneses and determined genetic mutations: 15 patients had mutations in NYX (Xl-CSNB1), 7 patients had mutations in TRPM1 (ar-CSNB1) and 5 patients had mutations in GRM6 (ar-CSNB1), 33 patients had mutations in CACNA1F (Xl-CSNB2) and 2 patients had mutations in CABP4 (ar-CSNB2). As expected, mainly CSNB1 patients complained of night blindness. This was rarely mentioned by CSNB2 patients, instead these patients frequently showed signs of photophobia. Refractive errors but also visual acuities were higher in CSNB1 patients compared to CSNB2 patients. Refractive errors did not change much after the age of five.
The original classification by Miyake (1986) of two types of CSNB was based on the DA curve and standard ERG measurements. The classification can be upheld for the different genetic causes considering the minor phenotype differences. However, based on the symptoms of especially the CSNB2 patients the name CSNB is confusing and not representative. To date, five genes are known to cause CSNB. This study showed that, the autosomal recessive inheritance is a major cause of CSNB1, and that additional disease genes are yet to be identified.
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