20p11.2-q11.2 locus

(OMIM has combined this disorder with PPCD1 (122000) based on genetic and clinical evidence.)

Early onset limbus-to-limbus corneal clouding is the outstanding feature.  Some asymmetry is often present.  Vision is minimally impaired if at all in many children but slow progression occurs and adults often become visually impaired.  Nystagmus does not develop.  Photophobia and tearing are common.  The corneal appearance can lead to the erroneous diagnosis of congenital glaucoma.  However, some infants actually do have congenital glaucoma as well leading some to suggest this may be a disorder of anterior chamber dysgenesis.  The edematous cornea may be of 2-3 times normal thickness.  It may appear generally hazy and sometimes has a diffuse ground glass appearance.  

The posterior surface often appears mottled and has been described as having a peau d'orange appearance.  The endothelium is attenuated or even absent histologically and abnormal, disorganized collagen fibrils have been found in a thickened Descemet layer by electron microscopy.  The remaining endothelial cells are often vacuolated and heaped in double layers, with some containing melanin granules.  Some atrophy and edema of the epithelium with partial loss of Bowman's can be seen histologically.