LINKAGE ANALYSIS IN A FAMILY WITH COMPLETE TYPE CONGENITAL STATIONARYNIGHT BLINDNESS WITH AND WITHOUT MYOPIA

A family is described with X-linked congenital stationary night blindn ess of the complete type (CSNB1) in which clinical variation between a ffected males resulted in diagnostic difficulties. In two affected mal e cousins, one had congenital nystagmus and myopia, while the other wa s initially thought to have retinitis pigmentosa with optic atrophy an d was hyperopic. The diagnosis of X-linked congenital stationary night blindness was established by clinical, psychophysical and electrophys iological criteria, and DNA markers flanking the CSNB1 locus were anal ysed in the family. The results show that both affected males have inh erited the same haplotype from their carrier mothers, excluding the po ssibility that a myopia gene in linkage disequilibrium with CSNB1 has recombined with this locus.