Given this, as well as the fact that three other variants in the OVOL2 promoter have been shown to segregate with the affected phenotype in two other families with PPCD (including the fourth family previously mapped to the PPCD1 locus) and one family initially diagnosed with autosomal dominant CHED that was mapped to the region on chromosome 20 containing OVOL2, promoter mutations in OVOL2 have been convincingly associated with PPCD1.[24, 25]. This evidence concerns the gene OVOL2 and congenital hereditary endothelial dystrophy type I.