Posterior pleomorphic corneal dystrophy
Introduction
Posterior polymorphic corneal malnutrition Posterior polymorphous dystrophy (PPD) represents a group of diseases with clinical and histopathological differences, one of which is similar to ICE syndrome. basic knowledge The proportion of illness: 0.002% Susceptible people: no specific population Mode of infection: non-infectious Complications: banded keratopathy
Cause
Posterior polymorphic corneal dystrophy
(1) Causes of the disease
A positive family history, bilateral ambulatory and incomplete post-elastic membrane histology found that the disease is a hereditary disease, most likely a hypothetical corneal endothelial cell or its basement membrane genetic defect, and is supported by the following findings: 1 abnormal The posterior elastic membrane posterior collagen layer (non-banded) suggests that endothelial cells have begun to change (recombinant and final differentiation) in the late fetal or early postnatal period. 2 The disease has been found to be associated with other congenital diseases such as keratoconus and Alport. Syndrome, suggesting that there may be a genetic defect in the basement membrane, 3 vagal keratinocyte populations progressively replace endothelial cells, these deficient denatured keratinocytes have abnormal ultrastructural and epithelioid cell characteristics, including microvilli, a small amount Mitochondria, cytoplasmic keratin filaments and desmosome contact, these cells are associated with small ring-shaped lesions of the posterior elastic membrane (with surrounding turbidity). 4 Most studies suggest that abnormal cells have epithelial-like cell characteristics and may originate from corneal endothelial cells. And undergoes a metaplastic process, or a response to changes in its basement membrane, however, the recurrence of the cornea after PPD keratoplasty Research presented in the disease may not defective endothelial cells themselves, but in the microenvironment surrounding cells, particularly aqueous humor.
(two) pathogenesis
The pathogenesis is unknown. It is speculated that corneal endothelial cells may be caused by obstacles during embryonic development. The fundamental defect of posterior pleomorphic dystrophy is the epithelioid cells behind the cornea. It is speculated that the interstitial cells that have evolved into the endothelium have evolved into various types. The potential ability of the cells can be changed into epithelial cells. The multi-layered and thickened collagen layer behind the posterior elastic layer is produced by such cells. This disease can be associated with anterior chamber cleft palate syndrome and wide Iris adhesion, suggesting that the eye may have a wider range of interstitial developmental disorders, due to the presence of a normal elastic layer of 110 m, suggesting that dysplasia begins in late pregnancy or neonatal period, and that stromal and epithelial edema is due to the loss of barriers by these cells. Function and pump function, surface degeneration, such as banded keratopathy, no specificity.
Membrane theory like ICE syndrome, once thought to be the pathogenesis of PPD secondary angle-closure glaucoma, abnormal endothelial cells or epithelial cells and their basement membrane-like substances, from the peripheral cornea down the iris cornea angle and to the iris Surface, followed by contraction of the membrane leading to iris corneal adhesion, angle closure, pupillary shift, uveal eversion and iris atrophy, the mechanism of secondary open angle glaucoma has not been confirmed, iris keratoscopy and ultrastructural studies found that The irises of these patients are embedded in the posterior trabecular mesh just before the scleral ridge. It is speculated that the iris acts as an oppressor, causing the trabecular mesh gap and trabecular column collapse and increasing the outflow resistance of the aqueous humor. These findings suggest that there is abnormal development of the iris corneal horn. And similar to the pathogenesis of certain congenital glaucoma.
Prevention
Posterior polymorphic corneal dystrophy prevention
There is no effective preventive measure for this disease. Early detection and early diagnosis are the key to the prevention and treatment of this disease.
Complication
Posterior polymorphic corneal dystrophy Complications banded keratopathy
Banded keratopathy, corneal decompensation, anterior adhesion around the iris.
Symptom
Posterior pleomorphic corneal dystrophy symptoms Common symptoms Herpes eye pressure increased vesicular edema pupil deformation nodules upper body weight loss, under...
1. General performance
PPMD is a familial disease, mostly autosomal dominant, also found in autosomal recessive inheritance, usually in the eyes of both eyes, also asymmetrical or unilateral, sometimes a corneal late pluripotent change, In the other eye, the cornea only has vesicles in a region. The age of onset is not easy to determine. There is no early symptoms in the early stage. It usually does not affect vision. Because it rarely produces matrix opacity or epithelial edema, the disease is described as stable, but It can also be performed slowly. For example, in older patients with normal vision, the accumulation of vesicles may increase, manifesting as polymorphism and thickening of the posterior elastic layer. In some patients, stromal edema gradually affects vision and develops into epithelial edema. , causing secondary banding keratopathy, and need to perform corneal transplantation, early no symptoms, usually does not affect vision, so it is generally found later.
2. Eye performance
Mainly for corneal lesions, iris and iris cornea angle can also be affected. The morphological changes of PPMD seen by slit lamp examination include small aggregated vesicles of the endothelium, large map-like blister-like changes, and the posterior elastic layer is gray turbid or different in size. The plaque is turbid without punctate corneal degeneration, and these changes are located at the level of the deep post-corneal elastic layer.
The simplest form of the disease is a cluster of vesicles, also known as posterior herpes or linear vesicles. 2 to 20 small (0.2 to 0.4 mm) unconnected round lesions gather together under light. Shaped like a pile of vesicles or blisters, surrounded by a diffuse gray halo, this lesion can appear anywhere behind the cornea, can remain stable for a long time, can also increase or regress, no effect on vision, when heavier, vesicles Gathering large map-like lesions, the larger map-like lesions are more serious types of clustered vesicles, and the gray halos are thicker and sometimes nodular, and the boundary between the circular or elliptical vesicles is more blurred. The lesions can be distributed in a variety of ways, from the peripheral ring to the local wedge, until the hard cheese-like pattern diffused behind the cornea. Under the wide-band illumination, the lesion has two translucent, scalloped ridges with scalloped edges. After the illumination method, the entire cornea is covered with a metallic foil-like orange peel. The matrix and epithelial edema are similar to other types of corneal edema. The matrix edema starts from the back and gradually becomes thicker. When the epithelial surface becomes irregular, Vision loss, In some cases, the wide peripheral iridocorneal adhesions occupy the 1mm range of the posterior part of the cornea, sometimes accompanied by a vitreous membrane, and the self-adhesive joint extends down to the iris surface, causing iris epithelial eversion and pupil deformation, and visible iris atrophy, slit lamp Check that the initial cornea is still transparent, and later the polymorphic map-like opaque body gathers. The thickened post-elastic layer, such as the posterior band-like accompanying sputum, causes endothelial decompensation and causes corneal edema. A small number of anterior adhesions around the iris appear, causing pupillary Deformation, pigmentation eversion and secondary glaucoma.
3. Systemic symptoms
Typical PPMD is associated with systemic abnormalities. It has been reported that PPMD may be a evidence of systemic basement membrane disease and has been found to be closely related to A1port syndrome, a basement membrane disease with congenital nephritis and hearing loss. Patients with Alport syndrome must have a full eye exam, including a special microscopy, and patients with PPMD should also have a renal function assessment and hearing test.
4. Secondary glaucoma
About 13% of patients with PPMD have glaucoma. The clinical manifestations of glaucoma are as follows: adult open angle glaucoma, adult angle closure glaucoma and infant glaucoma, iris with open angle and infant glaucoma. Corneal keratoscopy is normal, glaucoma with high iris angle closed, iris corneal keratoscopy can be seen iris keratoplasty, filamentous or columnar adhesions, eyes with closed angle can also have iris atrophy and pupil displacement, once along the appearance Wide adhesions in the range of 60° to 120°, usually with elevated intraocular pressure.
Examine
Posterior polymorphic corneal dystrophy
Genetic examination
Determine how it is inherited.
2. Pathological examination
Light microscopy can be used to detect the elastic membrane spindle-shaped tumor, and there are vesicle formation at the Descemet membrane level. A part of the PPMD case can form a wide peripheral anterior adhesion, and it can be attached to the Schwalbe line or the cornea forward. Combined with pupillary ectopic, iris pigment valgus and iris sparse, there are still cases where a translucent glass membrane extends from the posterior cornea to the iris. Electron microscopic observation shows abnormal corneal endothelium and deep Descemet membrane, and corneal endothelial cells Coverage, but ectopic corneal endothelial cell morphology is different from Chandler syndrome, with epithelial cell characteristics, including microvilli, some mitochondria, the presence of cytoplasmic keratin filaments and bridge junctions between multiple layers of cells, typically expressed as Descemet membrane Thick, and covered with multiple layers of collagen, in addition to abnormal endothelial cells, fibroblasts or epithelial cells, the clinical difference of corneal opacity or edema depends on the extent to which abnormal epithelial cells replace normal endothelial cell mosaics, special microscopy Techniques and cell culture techniques can determine the presence of endothelial cells and epithelial cells in patients with PPMD, and this Membrane with endothelium epithelial cells also found in the iris.
The structure of Descemet membrane can provide a history of embryonic and postnatal endothelial function. The changes of human Descemet membrane endothelial precipitation have been formed at birth and before and after birth. The pre-Descemet membrane is synthesized and connected in the fetal stage, and the Descemet membrane is formed in postpartum. , not connected, in the PPMD with abnormal posterior layer and normal anterior layer connection, the aforementioned abnormal accompanying periodic reorganization and alteration of endothelial cells is the cause of confusion.
Histological studies of the corneal endothelium in infants (2 to 3 months) have been reported. In fact, the posterior cell layer is predominantly epithelial, although endothelial cells can be seen, and lesions can be seen on the Descemt membrane in the epithelium. The presence of thin or missing membranes under the presence of the cells suggests that the disease begins in early pregnancy and is associated with the onset of Descemet membrane development.
1. Corneal endoscopic surface microscopy
The morphology of the lesion at the back of the cornea can be found.
2. Iris keratoscopy
The state of the front adhesion around the iris can be found, and the structure inside the corner is unclear.
Diagnosis
Diagnosis and differentiation of posterior polymorphic corneal dystrophy
Diagnosis can be determined based on clinical manifestations and genetic characteristics, but needs to be identified with similar diseases.
PPMD is often confused with other types of post-corneal dystrophy, such as Fuch endothelial dystrophy, congenital hereditary corneal dystrophy, and post-anamorphic corneal dystrophy, which is flaky turbidity through the gray-diffusing posterior matrix, occasionally iris Stretched to the 360° Schwalbe line and various iris anomalies, but without glaucoma, when corneal iris adhesions occur, both Axenfeld-Rieger syndrome and ICE syndrome should be considered, and many of the former two are attached to the prominent iris. On the Schwalbe ring, PPMD is often mixed with the post-corner Haab's line of congenital glaucoma, although the latter can be distinguished by thin areas of the margin, and endothelial cell microstructure is valuable in identifying PPMD and other diseases with anterior corneal abnormalities. of.
