Mutations in at least 3 genes on the X chromosome cause X-linked cone-rod dystrophy.
CORDX1 (304020) is caused by mutations in an alternative exon 15 (ORG15) of the RPGR gene (Xp11.4) which is also mutant in several forms of X-linked retinitis pigmentosa (300455, 300029). These disorders are sometimes considered examples of X-linked ocular disease resulting from a primary ciliary dyskinesia (244400).
CORDX2 (300085) is caused by mutations in an unidentified gene at Xq27. A single family has been reported.
CORDX3 (300476) results from mutations in CACNA1F. Mutations in the same gene also cause a form of congenital stationary night blindness, CSNB2A (300071). The latter, however, is a stationary disorder with significant nightblindness and mild dyschromatopsia, often with an adult onset, and is associated with high myopia. Aland Island Eye Disease (300600) is another allelic disorder.