Posterior polymorphous corneal dystrophy (PPCD) is a rare disorder involving metaplasia and overgrowth of corneal endothelial cells (Krafchak et al., 2005). In patients with PPCD, these cells manifest in an epithelial morphology and gene expression pattern, produce an aberrant basement membrane, and, sometimes, spread over the iris and nearby structures in a way that increases the risk for glaucoma. Symptoms can range from very aggressive to asymptomatic and nonprogressive, even within the same family. The age of diagnosis is, most often, in the second or third decade of life.
Clinically, PPCD is characterized by vesicles, bands, and polymorphous opacities at the level of the Descemet membrane and corneal endothelium. Peripheral anterior iris adhesions, iris atrophy, pupillary ectropion, and corectopia may also develop. Occasional severe visual disability results from secondary glaucoma or corneal edema. On ultrastructural examination, corneal endothelial cells show fibroblastic and epithelial-like transformation (summary by Liskova et al., 2012).
Genetic Heterogeneity of Posterior Polymorphous Corneal Dystrophy
Other forms of PPCD include PPCD2 (609140), caused by mutation in the COL8A2 gene (120252) on chromosome 1p34.3; PPCD3 (609141), caused by mutation in the ZEB1 gene (189909) on chromosome 10p; and PPCD4 (618031), caused by mutation in the GRHL2 gene (608576) on chromosome 8q22. [from
OMIM]