Eye defect

Introduction Eye defects are one of the symptoms and signs of hereditary progressive nephritis. Although eye defects are not as common as deafness, they are also common, with an incidence of 15% to 30%. The generation of these pathogenic gene carriers is related to the incomplete penetrance of heterozygotes, such as corneal opacity, small cornea, lens dislocation, cataract, glaucoma, macular dysplasia, strabismus, nystagmus, etc., involving the entire eye. In some dominant hereditary families, there are carriers of causative genes that do not manifest themselves but can transmit diseases to offspring. The generation of these causative gene carriers is related to the heterogeneity of heterozygotes, which is more common in women.

Cause

The cause of eye defects:

1. Sex-linked dominant inheritance is the main inheritance of this disease. Since the disease-causing gene is on the X chromosome, inheritance is related to gender. The mother's disease is also passed down, and the children have equal chances of getting sick, which is 50%. The father did not pass the child, but passed all the daughters. As such, there are more female patients than male patients in the family. But the male is more important than the female because the female has a normal homologous chromosome (heterozygous), while the male has no (semi-zygote). In the mid-to-late 1980s, some scholars began to explore the location of the disease-causing gene, and unanimously found that it was located in the middle of the long arm of the X chromosome (Xq22). However, this genetic mutation was not known at the time until Myers et al. in 1990 confirmed that the mutant gene is the gene of the collagen IV chain subunit 5(IV), COL4A5. However, in 1993, Zhou et al. found the gene IV of the collagen IV chain subunit 6 (IV) CoL4A6 at this Xq22 site, and confirmed that the COL4A6 mutation can also cause the disease.

2. Autosomal dominant inheritance 1/7 to 1/3 of the family is inherited in this way. Since the disease-causing gene is on the autosome, inheritance is not related to gender. The sick or the mother's children have the same chance of getting sick, about half of them, and the father can pass the child. The severity of the patient's condition is not related to gender, and the severity of the condition is similar between male and female. After discovering the location of the disease-causing gene in patients with this disease-linked dominant gene, people have been exploring the location of the disease-causing gene in patients with this genetic pattern. It is known that the genes of the other four subunits of the collagen IV chain are on the autosome: 1(IV) and 2(IV) genes COL4A1 and COL4A2 are located on chromosome 13; 3(IV) and 4(IV) genes COL4A3 and COL4A4 is located on chromosome 2. Which one or which genetic mutations caused the cost of the disease? It was only recently confirmed that it was COL4A3 and COL4A4 on chromosome 2.

3. Autosomal recessive inheritance (autosomal recessive inheritance) This disease has been reported in this disease after 1981, has been recognized, but such genetic family is rarely. Although the pathogenic gene is also on the autosome, the phenotype of the heterozygote is normal, but the homozygote shows the disease, so patients with clinical symptoms are often children of close relatives (parents are carriers of the disease gene, then The chance of having a child's illness is 1/4, and the chance of becoming a phenotype-bearing disease-bearing gene carrier is 1/2). The location of the disease-causing gene on the chromosome was also recently identified and is also COL4A3 and COL4A4 on chromosome 2.

an examination

Related inspection

Ophthalmoscopy and CT examination of the eye

Examination and diagnosis of eye defects:

1. Kidney performance:

The most important clinical manifestation of Alport syndrome is hematuria, and the affected male patients present with persistent microscopic hematuria. Within 20 years of age, many patients often have episodes of gross hematuria after upper respiratory tract infection. Affected women are often heterozygous, may exhibit intermittent hematuria, and 10% to 15% of heterozygous women have never had hematuria. Affected boys can develop hematuria within 1 year of age and are likely to occur as soon as they are born. A boy who has not had hematuria within 10 years of age is no longer possible.

2. Hearing loss:

Men who are deaf but not with kidney disease will not pass Alport syndrome to their offspring. Early hearing loss can only be found with a hearing test. Both sides of the hearing are reduced to the range of 2000 to 8000 Hz. The loss of hearing in male patients is progressive and will eventually spread to other frequencies, including the frequency of vocalization. In female patients, hearing loss is less and tends to occur at a greater age.

3. Eye defects:

Although eye defects are not as common as deafness, they are also common, with an incidence of 15% to 30%. The anterior cone lens (i.e., the central portion of the lens forms a conical anterior sac) is essentially a characteristic lesion of the Alport syndrome. Nielson found that all patients with conical crystals were able to obtain evidence of chronic nephritis and sensorineural deafness after careful examination.

Differential diagnosis

Symptoms of eye defects that are confusing:

Lens shrinkage: complicated cataract associated with anterior segment disease, slow progression of the lesion, such as local inflammation can be controlled, turbidity can be stable for a long time without development. As the disease progresses, the degree and extent of turbidity continue to increase and expand, eventually involving the entire lens. During the progression, crystalline substances or calcareous deposits may appear in the lens or in the capsule, and in the advanced stage, the lens may shrink and even calcify.

Pupil deformation: The pupil deformation refers to the abnormal shape of the pupil, or the abnormal reaction of the pupils on both sides. Normally round, both sides are equal, and the responses of the pupils on both sides are synchronized. It can be elliptical in glaucoma or intraocular tumors; the shape can be irregular when the iris is stuck.

Congenital aniridia: Aniridia is a developmental disorder in both eyes. It is characterized by congenital iris dysplasia or lack of normal iris. It can also be associated with various eye diseases such as corneal opacity, small cornea, and lens dislocation. , cataract, glaucoma, macular dysplasia, strabismus, nystagmus, etc., involving the entire eye.

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