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Clinicopathologic correlation and genetic analysis in a case of posterior polymorphous corneal dystrophy
Sayoko E Moroi1, Parag A Gokhale, Miriam T Schteingart
1Department of Ophthalmology and Visual Sciences, W. K. Kellogg Eye Center, University of Michigan, Ann Arbor, Michigan 48105, USA. smoroi@umich.edu
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, alpha-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.
Insights
This study details a rare case of posterior polymorphous corneal dystrophy (PPMD) with a unique retrocorneal membrane. The family
Area of Science:
- Ophthalmology
- Genetics
- Histopathology
Background:
- Posterior polymorphous corneal dystrophy (PPMD) is a rare inherited eye condition affecting the cornea.
- Clinical presentation and genetic underpinnings of PPMD are not fully understood, particularly in atypical cases.
Observation:
- A patient with PPMD exhibited a prominent retrocorneal membrane extending onto the crystalline and intraocular lenses over 17 years.
- Histopathology and electron microscopy confirmed endothelial transformation, differentiating it from epithelial downgrowth.
- Autosomal dominant inheritance was suggested within the family (UM:139).
Findings:
- Genetic analysis excluded known PPMD, CHED1, CHED2 loci, and the COL8A2 gene, indicating a novel genetic basis.
- The unusual retrocorneal membrane growth is a previously unreported feature in PPMD cases.
Implications:
- This case expands the clinical spectrum of PPMD, highlighting unusual membrane formation.
- The findings suggest the existence of a new genetic locus for PPMD, warranting further investigation.
- Understanding these genetic variations is crucial for accurate diagnosis and potential therapeutic strategies in corneal dystrophies.