Clinicopathologic correlation and genetic analysis in a case of posterior polymorphous corneal dystrophy

Abstract

Purpose To evaluate the clinical history, histopathology, and genetics of posterior polymorphous corneal dystrophy (PPMD) in a woman with a prominent retrocorneal membrane. Design Observational case report and genetic analysis of her family, UM:139. Methods Records were reviewed from a case and associated family members. The diagnosis of PPMD was based on clinical examination, immunohistochemical staining, electron microscopy, and screening of genetic markers from regions previously reported to be associated with PPMD. Results Over 17 years, the proband with PPMD had 25 ocular procedures performed for glaucoma, cataract, cornea, retina, and postoperative problems. A prominent retrocorneal membrane grew onto the crystalline lens and intraocular lens (IOL). Histopathology revealed stratified epithelial-like cells on iris from an iridectomy and stratified corneal endothelium on a corneal button. Electron microscopy on the cornea revealed microvilli, tonofilaments, and desmosomes consistent with endothelial transformation, which was confirmed by positive anticytokeratin (CK) AE1/AE3 and CAM 5.2 immunoreactivity. Negative immunoreactivity in epithelium and positive in endothelium with anti-CK 7 supported the diagnosis of PPMD rather than epithelial downgrowth. Multiple relatives were affected with PPMD with apparent autosomal dominant inheritance, but surprisingly, the PPMD, congenital hereditary endothelial dystrophy 1 (CHED1) and CHED2 loci on chromosome 20 and the collagen, type VIII, α-2 (COL8A2) gene were excluded by linkage and haplotype analyses. Conclusions We are unaware of previous PPMD reports describing the unusual feature of a retrocorneal membrane extending onto the crystalline lens and IOL. In addition, this family suggests another PPMD locus.