[X-chromosomal hereditary night blindness: detection of carriers by segregation analysis with linked DNA markers]

Congenital stationary night blindness is a rare disease with autosomal dominant, autosomal recessive, or X-linked recessive inheritance. The X-chromosomal form is frequently associated with myopia. Female carriers have no symptoms of visual impairment and therefore cannot be identified clinically. The close link recently described between the disease locus and the DXS7 locus, mapped in Xp11.3, as well as other marker loci from this chromosomal region, permits indirect genotype analysis and thus identification of the carriers; with the information thus obtained, improved genetic counseling is possible. The authors studied a large Swiss family with the X-linked trait. Segregation analysis was performed with DXS7 as well as two flanking markers, DXS255 and OTC. It was thus possible to determine the degree or probability of several female members of the family being carriers.