Posterior Polymorphous Corneal Dystrophy

Synonyms

Posterior polymorphous dystrophy (PPMD); Schlichting dystrophy

Definition

Endothelial corneal dystrophy.

Etiology

Posterior polymorphous corneal dystrophy (PPCD) is an autosomal dominantly inherited corneal dystrophy. Three genetic loci – PPCD 1 through 3 – have been isolated to chromosomes 20, 1, and 10, respectively. Mutations in COL8A2 (collagen type VIII alpha 2) and ZEB1 (two-handed zinc-finger homeodomain transcription factor 8) are responsible for PPCD 2 and PPCD 3. The gene implicated for PPCD 1 has not been isolated.

Clinical Presentation

The onset of PPCD is in early childhood. Patients often present with asymmetric, deep corneal lesions of various morphologies including nodular, vesicular, and blister-like lesions. Patients can also present with deep stromal broadbands with scalloped edges have been termed “railroad tracks” (Fig. 1a, b). Geographic-shaped lesions at the level of Descemet’s membrane are often present. Stromal and epithelial edema can be variably...