X-linked endothelial corneal dystrophy (XECD) is a rare form of corneal dystrophy described first in 2006, based on a 4-generation family of 60 members with 9 affected males and 35 trait carriers, which led to mapping the XECD locus to Xq25.^[1] It manifests as severe corneal opacification or clouding, sometimes congenital, in the form of a ground glass, milky corneal tissue, and moon crater-like changes of corneal endothelium. Trait carriers manifest only endothelial alterations resembling moon craters.^{[citation needed]}

As of December 2014, the molecular basis for this disease remained unknown, although 181 genes were known to be within the XECD locus, of which 68 were known to be protein-coding.^[2][3]