X-linked juvenile retinoschisis

X-linked juvenile retinoschisis is a genetic eye disorder that impairs normal vision. This disorder affects the retina, which is a specialized light-sensitive tissue that lines the back of the eye. Damage to the retina impairs the sharpness of vision (visual acuity). Typically, X-linked juvenile retinoschisis affects cells in the central area of the retina called the macula. The macula is responsible for sharp central vision, which is needed for detailed tasks such as reading, driving, and recognizing faces. X-linked juvenile retinoschisis is one type of a broader disorder called macular degeneration, which involves disruption in the normal functioning of the macula. Occasionally, side (peripheral) vision is affected in people with X-linked juvenile retinoschisis.

X-linked juvenile retinoschisis occurs almost exclusively in males. It is usually diagnosed when affected boys start school and poor vision and difficulty with reading become apparent. In more severe cases, eye squinting and involuntary movement of the eyes (nystagmus) can be seen in infancy. Visual acuity remains unchanged in most people between their teenage years and their forties or fifties, when a significant decline in visual acuity typically occurs. Rarely, severe complications develop, such as separation of the retinal layers (retinal detachment) or leakage of blood vessels in the retina (vitreous hemorrhage). These eye abnormalities can cause impaired vision or blindness.

The prevalence of X-linked juvenile retinoschisis is estimated to be 1 in 5,000 to 25,000 males worldwide.

Mutations in the RS1 gene cause most cases of X-linked juvenile retinoschisis. The RS1 gene provides instructions for producing a protein called retinoschisin, which is found in the retina. Studies suggest that retinoschisin plays a role in the development and maintenance of the retina and in specialized cells within the retina that detect light and color (photoreceptor cells).

RS1 gene mutations lead to a reduced amount of retinoschisin, which can cause tiny splits (schisis) or tears to form in the retina. This damage often forms a "spoke-wheel" pattern in the macula, which can be seen during an eye examination. These abnormalities are typically seen in the area of the macula, affecting visual acuity, but can also occur in the sides of the retina, resulting in impaired peripheral vision.

Some individuals with X-linked juvenile retinoschisis do not have a mutation in the RS1 gene. In these individuals, the cause of the disorder is unknown.

This condition is inherited in an X-linked recessive pattern. The gene associated with this condition is located on the X chromosome, which is one of the two sex chromosomes. In males (who have only one X chromosome), one altered copy of the gene in each cell is sufficient to cause the condition. In females (who have two X chromosomes), a mutation would have to occur in both copies of the gene 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 much more frequently than females. A striking characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons.