OVOL2 and posterior polymorphous corneal dystrophy: To date, approximately 30% to 40% of PPCD cases have been attributed to 40 unique heterozygous nonsense and frameshift mutations and hemizygous copy number variants involving the zinc finger E-box binding homeobox 1 gene (ZEB1) on chromosome 10 that likely result in ZEB1 haploinsufficiency.[2–12] However, the identification of the genetic basis of PPCD1 (MIM ID #122000) has proven to be more elusive, in spite of the fact that linkage to the PPCD1 locus was reported almost a decade before linkage to the PPCD3 locus was described.[13, 14]