[Incomplete congenital stationary night blindness (CSNB). An important differential diagnosis of congenital nystagmus].
BACKGROUND
Classifying congenital nystagmus in the absence of biomicroscopically detectable abnormalities of the eye, and in an otherwise healthy child is difficult, especially early in life. At that age, nystagmus and visual loss may be the predominant symptoms of congenital stationary night-blindness. Unless night-blindness is specifically asked for or an ERG performed the correct diagnosis may be missed.


METHODS
We present the clinical data of two families with X-linked incomplete CSNB previously undiagnosed. ERG recordings in both families were suggestive of CSNB. The ERG of the obligate carrier was normal. In an attempt to distinguish between the complete and the incomplete type, and to identify further carrier signs, scotopic perimetry and dark adaptation were performed in both affected males and carriers. Scotopic perimetry allows to test the rod-mediated visual pathway in its spatial distribution.


RESULTS
In affected males with non-recordable ERGs scotopic perimetry and dark adaptation disclosed residual rod function indicating an incomplete type. In carriers, there was a sensitivity loss at 600 nm, which may be a new carrier sign.


CONCLUSIONS
The correct diagnosis of the different forms of CSNB together with the identification of carriers is important for (1) genetic counselling and (2) linkage studies to identify the gene(s) for CSNB.
Lorenz
B
B
Klinik und Poliklinik für Augenheilkunde, Klinikum der Universität Regensburg.
Andrassi
M
M
Miliczek
K D
KD
D000293:Adolescent; D000328:Adult; D002648:Child; D003623:Dark Adaptation / Q000235:genetics / Q000502:physiology; D005260:Female; D006580:Genetic Carrier Screening; D008040:Genetic Linkage; D005820:Genetic Testing; D006801:Humans; D008297:Male; D009755:Night Blindness / Q000175:diagnosis / Q000235:genetics* / Q000503:physiopathology; D009759:Nystagmus, Pathologic / Q000175:diagnosis / Q000235:genetics* / Q000503:physiopathology; D010375:Pedigree; D012307:Risk Factors; D012729:Sex Chromosome Aberrations / Q000175:diagnosis / Q000235:genetics* / Q000503:physiopathology; D058609:Visual Field Tests; D014960:X Chromosome