Posterior polymorphous corneal dystrophy (PPCD; sometimes also ''Schlichting dystrophy'') is a type of corneal dystrophy, characterised by changes in

Descemet's membrane Descemet's membrane ( or the Descemet membrane) is the basement membrane that lies between the corneal proper substance, also called stroma, and the endothelial layer of the cornea. It is composed of different kinds of collagen (Type IV and VIII) ...

and endothelial layer. Symptoms mainly consist of decreased vision due to corneal edema. In some cases they are present from birth, other patients are asymptomatic. Histopathological analysis shows that the cells of endothelium have some characteristics of epithelial cells and have become multilayered. The disease was first described in 1916 by Koeppe as ''keratitis bullosa interna''.

Genetics

PPCD type 2 is linked to the mutations in

COL8A2 Collagen alpha-2(VIII) chain is a protein that in humans is encoded by the ''COL8A2'' gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation ...

, and PPCD type 3 mutations in

ZEB1 Zinc finger E-box-binding homeobox 1 is a protein that in humans is encoded by the ''ZEB1'' gene. ZEB1 (previously known as TCF8) encodes a zinc finger and homeodomain transcription factor that represses T-lymphocyte-specific IL2 gene expression ...

gene, but the underlying genetic disturbance in PPCD type 1 is unknown.

Pathophysiology

Vacuoles are demonstrated in the posterior parts of the

cornea The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical power ...

. 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 Glaucoma is a group of eye diseases that result in damage to the optic nerve (or retina) and cause vision loss. The most common type is open-angle (wide angle, chronic simple) glaucoma, in which the drainage angle for fluid within the eye rem ...

Genetics

Pathophysiology

Diagnosis

See also

References

External links