XLRS is typically diagnosed in school-aged children and, because of its X-linked inheritance, occurs almost exclusively in males. It has an estimated prevalence among males of 1:5000 to 1:20,000. The condition is probably present earlier, but the diagnosis may be delayed because of cognitive restrictions in visual testing; patients often present when they fail their vision screening tests as they reach school age.
Vision loss is progressive and begins with mild impairment early in life. While the patient will not present with acute vision loss, they can suffer from other complications, such as vitreoretinal traction, neovascular glaucoma, or vitreous hemorrhage.[1,7] Vision loss is usually equal bilaterally but can be asymmetric when other complications are present. Retinoschisis of the macula is present in all patients with XLRS, but only in the periphery of about 50% of them.
Foveal schisis is the most common clinical finding in XLRS patients younger than 30 years of age.[1,7] The folds in the retina appear as radial or stellate lines around the fovea (as shown in Figure 1), or less commonly may present as holes or bullous changes in the periphery. In patients older than 30 years, the clinical finding shifts to nonspecific retinal abnormalities, as opposed to the typical spoke-wheel pattern in younger patients.
An electroretinogram can be used to confirm the diagnosis of XLRS. Patients typically present with reduced b-wave amplitude and conserved a-wave amplitude throughout the retina and not just confined to areas of schisis. With increasing age, a-wave amplitude can become decreased.
OCT is used to diagnose and monitor XLRS. OCT allows for cross-sectional visualization of the retina and helps differentiate XLRS from other retinal complications like retinal detachment, cone dysfunction, or macular dystrophies. OCT usually shows cystic spaces in the outer plexiform layer of the macula and can extend beyond areas with schisis that are visible ophthalmoscopically.
Genetic testing provides important information in the counseling of both parents and children. The RS1 gene encodes the protein retinoschisin, which is responsible for helping maintain the integrity of the retina and is typically expressed in photoreceptor and bipolar cells. Without functioning retinoschisin, the retina splits and creates folds in the retina that contain microcysts. There are a number of XLRS-causing mutations of the RS1 gene, but phenotypic variability between the different mutations is not observed. Because the gene is X-linked, nearly all affected are males, although it can show up in females in incidences of consanguinity. Female carriers of the gene show no clinical abnormalities.
Because of the high genetic variability of XLRS, prognosis is also variable. Patients diagnosed with XLRS should be educated on the risks of vitreous hemorrhage and retinal detachment. Low vision aids can be prescribed.
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Cite this: A Boy With Suddenly Failing Vision - Medscape - Apr 18, 2018.