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 ... 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. - 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, and PPCD3 (609141), caused by mutation in the ZEB1 gene (189909) on chromosome 10p.
Vacuoles are demonstrated in the posterior parts of the cornea by slit-lamp examination. The vesicles are located on the endothelial surface. The corneal endothelium is normally a single layer of cells that lose their mitotic potential after development ... Vacuoles are demonstrated in the posterior parts of the cornea by slit-lamp examination. The vesicles are located on the endothelial surface. The corneal endothelium is normally a single layer of cells that lose their mitotic potential after development is complete. In posterior polymorphous corneal dystrophy, the endothelium is often multilayered and has several other characteristics of an epithelium, including the presence of desmosomes, tonofilaments, and microvilli. These abnormal cells retain their ability to divide and extend onto the trabecular meshwork to cause glaucoma in up to 40% of cases (Heon et al., 1995). This condition was first described by Koeppe (1916) under the name of keratitis bullosa interna, an appropriately descriptive designation. Schlichting (1941) noted depressions, vesicles, and polymorphous opacities in the Descemet membrane, with opacities in the deepest layers of the stroma, in father and 4-year-old daughter. Theodore (1939) reported affected members in 3 generations. Rubinstein and Silverman (1968) observed a mother and 2 children affected. The mother and 1 child had rupture of the Descemet membrane, and the mother had glaucoma. McGee and Falls (1953) reported a family. In a photo essay, Anderson et al. (2001) reviewed the clinical and histopathologic overlaps between posterior polymorphous membranous dystrophy and iridocorneal endothelial syndrome. PPCD is bilateral, usually asymptomatic, and usually nonprogressive; it occurs at all ages and shows no sex predilection. Sporadic iridocorneal endothelial syndrome is usually unilateral, symptomatic, and progressive; it presents at middle age and is more common in women. Corneal edema, glaucoma, and iris changes are more common in the iridocorneal endothelial syndrome. In PPCD, endothelial cells are more likely to display epithelial-like characteristics. The authors concluded that it is difficult to distinguish between these 2 endotheliopathies. They thought that an insult during embryogenesis might result in PPCD, whereas an insult later in corneal development might result in the iridocorneal endothelial syndrome. They also noted that the herpes simplex virus had been implicated as a cause in the iridocorneal endothelial syndrome. Jirsova et al. (2007) demonstrated that the abnormal endothelium of PPCD patients expressed a mixture of cytokeratins, with KRT7 (148059) and KRT19 (148020) predominating. In terms of KRT composition, the aberrant PPCD endothelium shared features of both simple and squamous stratified epithelium with a proliferative capacity. Jirsova et al. (2007) suggested that the wide spectrum of KRT expression was most probably not indicative of the transformation of endothelial cells to a distinct epithelial phenotype, but more likely reflected a modified differentiation of metaplastic epithelium.
Heon et al. (2002) identified mutations in the VSX1 homeobox gene in patients with either keratoconus (148300) or PPCD. Two sequence changes (L159M, 605020.0003 and G160D, 605020.0002) were associated with keratoconus and PPCD, respectively, and involved a region ... Heon et al. (2002) identified mutations in the VSX1 homeobox gene in patients with either keratoconus (148300) or PPCD. Two sequence changes (L159M, 605020.0003 and G160D, 605020.0002) were associated with keratoconus and PPCD, respectively, and involved a region adjacent to the homeodomain. One of the mutations (R166W; 605020.0001) responsible for keratoconus altered the homeodomain and impaired DNA binding.