OMIM ID:
Corneal Dystrophy, Posterior Polymorphous 1
Alternate Names
Defective Genes
Clinical Characteristics
Ocular Features
This form of corneal dystrophy is often asymptomatic but some patients experience endothelial decompensation and corneal edema, which may even be seen soon after birth. The edema may extend into the epithelium. The basic mechanism entails metaplasia of endothelial cells which seem to acquire some characteristics of epithelial cells. Posterior corneal lesions of variable morphology appear in various patterns and are often surrounded by grayish halos. When these become confluent the corneal edema is more severe and may resemble a congenital endothelial dystrophy. The endothelial cell count is often low. The Descemet layer also becomes abnormal. The posterior border of the cornea appears nodular and grayish in color, often in a geographic pattern. Surprisingly, endothelial function often is maintained and patients may remain asymptomatic for many years.
Some patients have features of anterior chamber dysgenesis with iris anomalies, anterior synechiae, and glaucoma. It is also sometimes confused with EDICT syndrome (614303).
Systemic Features
No systemic disease is associated with this disorder.
Genetics
Inheritance
This is a genetically heterogeneous autosomal dominant disorder caused by several mutations including the promotor of OVOL2 at 20p11.23 responsible for PPCD1 described here. Another locus for this disease has been mapped to 20q11, the same locus responsible for congenital hereditary corneal edema 1 (CHED1) and it is possible that these are allelic or clinical variants of the same mutation. The latter is made more likely by the fact that both disorders have been found in relatives. OMIM has combined the entities CHED1 and PPCD1 as a single disorder (122000).
For other forms of posterior polymorphous corneal dystrophy see, PPCD2 (609140) and PPCD3 (609141).
Pedigree
Autosomal dominant
Autosomal dominant disorders require only one mutation for the disease to be expressed. Since an affected parent has two chromosomes, only one of which has the mutant gene, parents can expect that half (50%) of their children will receive that one and inherit the disease. It is common for individuals that inherit the mutation, however, to not have evidence of the disease (nonpenetrance).
Autosomal dominant inheritance leads to a vertical pattern of transmission