Overview Of X-Linked Juvenile Retinoschisis
Occuring almost exclusively in males, X-linked juvenile retinoschisis (XJR) is a condition characterized by the impaired vision that begins during childhood. This disorder affects the retina, which is a light-sensitive tissue that thinly lines the back of the eye. Damage to the retina impairs the sharpness of vision in both eyes. Oftentimes, X-linked juvenile retinoschisis affects a portion of the eye known as the macula, which happens to be located in the central area of the retina. The macula is responsible for our sharp central vision which helps us to complete various detailed tasks.
These tasks may include:
- Recognizing Faces.
X-linked juvenile retinoschisis is also one type of a more broad disorder called macular degeneration, in which the macula cannot function as normal. At times, X-linked juvenile retinoschisis may alter peripheral vision. Medical professionals typically diagnose boys affected by X-linked juvenile retinoschisis when they begin school. Poor vision and difficulty reading become apparent at this time. In more severe cases, eye squinting and involuntary movement of the eyes (nystagmus) may also begin during infancy.
Other early features of X-linked juvenile retinoschisis include eyes that point in different directions (strabismus). Hyperopia, or farsightedness, may also be an early feature of this condition. Visual acuity often declines in childhood and adolescence but then stabilizes throughout a person’s adulthood. However, once a man reaches his fifties or sixties, a significant decline in visual activity typically occurs. Sometimes, severe complications can develop. Separation of the retinal layers (retinal detachment) or leakage of the blood vessels within the retina (vitreous hemorrhage) are two examples. These eye abnormalities can further impair vision or results in blindness.
Commonly Associated With:
- Congenital X-linked retinoschisis.
- Degenerative retinoschisis.
- X-linked retinoschisis.
Causes Of X-Linked Juvenile Retinoschisis
Mutations in the RS1 gene tend to cause most cases of X-linked juvenile retinoschisis. The RS1 gene gives instructions for creating a protein called retinoschisin, which is in the retina. Studies suggest that retinoschisin plays a part in the development and maintenance of the retina. For example, the protein likely helps in the organization of cells in the retina by attaching these cells together (cell adhesion).
RS1 gene mutations result in either a decrease in reinoschisin or a complete loss of functional retinoschisin. This disrupts the maintenance and organization of cells within the retina. As a result, tiny splits (schisis) or tears may form. This damage often creates a “spoke-wheel” pattern in the macula, which is possible to observe during an eye examination. In half of the affected individuals, these abnormalities can take place in the area of the macula, affecting visual acuity. In the other half of cases, the schisis occurs in the sides of the retina, which results in an impaired peripheral vision. Sometimes, individuals with X-linked juvenile retinoschisis do not have a mutation in the RS1 gene. The cause of the disorder in these individuals is unknown.
Professionals estimate the prevalence of X-linked juvenile retinoschisis to be roughly 1 in 5,000 to 25,000 men worldwide. This condition is inherited in an X-linked recessive pattern, meaning the gene associated with this condition is found on the X chromosome. In males (who carry only one X chromosome), one altered copy of the gene in each cell is sufficient enough to cause this condition. In females (who have two X chromosomes), a mutation would have to occur in both copies of the gene in order to cause the disorder. Because it is unlikely that females will have two altered copies of this gene, males are affected by X-linked recessive disorders more often than females. In the case of X-linked inheritance, fathers are not able to pass X-linked traits to their sons.