CLINICAL DIVERSITY AND CHROMOSOMAL LOCALIZATION OF X-LINKED CONE DYSTROPHY (COD-I)

X-linked progressive cone dystrophy (COD1) causes progressive deterior ation of visual acuity, deepening of central scotomas, macular changes , and bull's-eye lesions. The cone electroretinography (ERG) is variab ly abnormal in affected males, and the rod ERG may also be abnormal. T he clinical picture of heterozygous females ranges from asymptomatic t o a widespread spectrum of cone-mediated dysfunction. A prior linkage study demonstrated linkage between the COD1 locus and the marker locus DXS84, assigned to Xp21.1, with no recombination. In the present stud y, we have clinically characterized a large four-generation family wit h COD1 and have performed a linkage analysis using seven polymorphic m arkers on the short arm of the X chromosome. No recombination was obse rved between the disease and the marker loci DXS7 and MAOA, suggesting that the location of COD1 is in the region Xp11.3, distal to DXS84 an d proximal to ArAF1.