Lattice corneal dystrophy
Introduction
Introduction to lattice corneal malnutrition Lattice corneal dystrophy (lattice cornealdystrophy) is a kind of bilateral symmetrical corneal stroma with grid-like opacity and severe visual impairment of hereditary keratopathy. Currently, there are five clinical types of I, II, III, IIIA and IV. Type I clinical is more common, and many cases have been reported in China. basic knowledge The proportion of illness: 0.0003%-0.0005% Susceptible people: children born in 2 to 7 years old Mode of infection: non-infectious Complications: radial nerve palsy
Cause
Lattice corneal malnutrition
(1) Causes of the disease
Type I, II, IIIA, IV are autosomal dominant inheritance, of which type I penetrance can reach 100%, type III is autosomal recessive, occasionally sporadic cases, the exact cause is unknown, currently considered I, IIIA, Type IV is associated with mutations in the BIGH3 gene, and type II is associated with mutations in the GSN gene (gelsolin gene).
(two) pathogenesis
In 1997, Munier et al. detected that the disease was caused by a missense mutation in the TGFBI gene product, corneal epithelial (KE), on the long arm 5q31 of chromosome 5. This defective corneal epithelin caused epithelial cells to excrete a sugar. Protein under the epithelium may form amyloid deposits in the parenchyma by means of the activity of corneal cells. The amyloid is a non-collagen fibrin containing 2% to 5% carbohydrates, and the deposit of lattice corneal dystrophy There is an AP protein. It is speculated that this deposit may be directly produced by abnormal corneal cells; but it may also be that abnormal corneal cells release lysosomal enzymes, which promote the denaturation of collagen or aminodextran in nature, and the denatured products evolve into amyloid fibers. Filaments are deposited on the substrate layer.
Prevention
Lattice corneal malnutrition 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
Lattice corneal dystrophy complications Complications
In addition to corneal lesions, it is also accompanied by systemic amyloidosis, such as progressive cranial nerves and peripheral nerve palsy, dry skin itching, and loose eyelid skin.
Symptom
Lattice-shaped corneal dystrophy symptoms Common symptoms Amyloidosis paralysis corneal epithelial erosion nodules upper body weight loss, under... Drop-shaped cornea
The disease is early onset, before the age of 10 (more than 2 to 7 years old), the symptoms of recurrent corneal epithelial erosion and gradually worsening vision loss, often after 10 years old, many patients in 30 ~ 40 At the age of age, corneal transplantation surgery is required. Most of the disease is symmetrical in both eyes, but it is also reported as monocular. In the early stage, the corneal central axis is slightly diffuse opacity under the slit lamp, and the parenchyma is shallow in the paracentral cornea. There are irregular branch-like strips and point-like nodules in the Bowman layer, which gradually expand and thicken, and are interwoven into a net or a lattice with nodules. This lattice line and nodules can be seen by illumination after illumination. It is a refraction double contour with an optically transparent core. This kind of refractive translucent lattice line is a characteristic lesion of the disease. Another non-refractive round or oval shape is visible under the corneal epithelium. Limiting turbid spots of different sizes, the above various lesions can be extended to the periphery (generally not reaching the limbus) and deep in the deep; or the upper cortex can be stretched to make the surface of the corneal epithelium irregular, plus the scar formed by the shallow cornea. More heavy The degree of opacity of the film, that it is sometimes late with patchy appearance and very similar granular corneal dystrophy, late due to scar formation, sensitivity decreased, epithelial erosion symptoms gradually disappear.
1. Type I
Larger than childhood, the lesions are symmetrical, the initial symptoms can be no symptoms, the disease progresses slowly, often after 10 years of age, eye irritation caused by recurrent epithelial erosion and progressively worsened vision loss, to 20 to 30 years old vision Most of them have been seriously damaged. In the early stage of slit lamp examination, there is a slight diffuse turbidity in the central part of the cornea. In the shallow layer and the Bowman layer, there are irregular branch-like white strips and turbid spots. These thin strips and turbidity points gradually expand and thicken. Increased, interlaced into a grid, with nodular opacity points in between, visible in the posterior illumination method, the grid lines and nodules are refractive double contours, which have an optically transparent core, which is the disease Characteristic lesions, the above lesions can be extended to the periphery (generally not reaching the limbus) and the deep deep layer, or can be extended to the upper cortex, making the surface of the cornea irregular, dense disc-like opacity in the center of the late cornea, covering the original grid Lines, and sometimes with plaque and granular corneal dystrophy are difficult to identify, you need to carefully look for refractive branching lattice lines to distinguish.
2. Type II
For familial amyloidosis, the corneal lesions start late, generally after the age of 20, the corneal grid-like lesions are thinner, less rare, and the visual impairment is also less, rarely requiring corneal transplantation, patients with corneal lesions It is also accompanied by systemic amyloidosis such as progressive cranial nerves and peripheral nerve palsy, dry skin itching, and loose eyelid skin.
3. Type III and Type IIIA
The onset is also late, the corneal grid-like lesions are coarser, but the visual impairment is lighter, and there is no recurrent corneal epithelial erosion in the type III disease.
4. Type IV
It is also an atypical lattice-like corneal dystrophy characterized by turbidity in the deep stromal layer.
Examine
Lattice corneal dystrophy
1. Genetic examination.
2. Pathological examination:
(1) Light microscopy: The thickness of the epithelial cells is different, the arrangement is irregular, the Bowman layer is broken, the morphology of the corneal parenchyma is distorted, and many eosinophilic fusiform opaque deposits on the epithelial cell layer and Bowman. Between the layers, the sediment is scattered in the parenchyma, but mainly in the superficial layer, while the Descemet membrane and the endothelial cell layer remain normal. The histochemical method shows that the sediment is amyloid: Congo red, purple When stained with thioacridine yellow, all three were positive. Under the polarizing microscope, the lesions showed dichroism and birefringence. The immunohistochemical method also confirmed that the sediment was amyloid.
(2) Electron microscopy: epithelial basal cells degenerate, vacuoles are formed in the cytoplasm, epithelial basement membrane becomes thick and discontinuous, hemidesmosome disappears, Bowman layer is thick and thin, and there is rupture, corneal cells in parenchymal layer The number is reduced, the cytoplasmic vacuoles are formed, the endoplasmic reticulum and the Golgi apparatus in the cytoplasm are enlarged, and the deposits in the subepithelial and parenchymal layers are observed by transmission electron microscopy, which are composed of many extracellular fine electron density filaments. The fibrils are not branched, and the diameter is 8 to 10 nm, and most of them are integrated into one line (which can explain the double-fold and two-color phenomenon displayed clinically), and a few are aggregated.
Diagnosis
Diagnosis and identification of lattice corneal dystrophy
The diagnosis can be determined based on typical clinical findings and the results of the auxiliary examination.
The progression of the lesion to a certain stage requires identification of plaque and granular corneal dystrophy.
