Congenital stationary night blindness: Report of an autosomal recessive family and linkage analysis

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Abstract
Congenital stationary night blindness (CSNB) is a group of rare, non‐progressive conditions of the retina characterized by abnormal rod function causing impaired night vision. Among them, the Schubert–Bornschein subgroup, itself divided into a complete and an incomplete form, is characterized by a specific electrophysiological pattern. Complete, Schubert–Bornschein CSNB is usually transmitted as a monogenic trait, and most familial cases result from mutations of the NYX gene located on the X chromosome. We report a very rare family with consanguineous, first‐cousin parents, where a son and a daughter are affected with this condition, indicating autosomal recessive inheritance. As the family was too small for genome‐wide linkage, we considered several candidate loci, including the sidekick SDK1 and SDK2 genes. The latter determine lamina‐specific connectivity in the retina, a histological substrate of the ON pathway implicated in complete, Schubert–Bornschein CSNB. Although linkage was excluded in our family, observations like the present one may lead to the identification of a new molecular cause for this condition.