Mapping X-linked ophthalmic diseases. Provisional assignment of the locus for choroideremia to Xq13-q24.

Choroideremia (McK 30310), an X-linked hereditary retinal dystrophy, causes nyctalopia, progressive visual field loss, and ultimately central blindness in affected males in early adulthood. We have used restriction fragment length polymorphisms from the X-chromosome to localize the region of the mutation for choroideremia in three families with this disorder. One polymorphic marker, DXYS1, located within Xq13-q21, shows no recombination with choroideremia at a LOD score of 5.78. Thus choroideremia maps within 9 centiMorgans of DXYS1 at 90% probability. Another marker, DXS11, located at Xq24-q26, shows no recombination with choroideremia but at a smaller LOD score of 1.54. These results suggest that the locus for choroideremia is distal to DXYS1 and between the two markers in the region Xq13-q24. This information may be useful for antenatal diagnosis, isolation of the mutant gene, and development of a rational therapy for the disorder.