The NM_000330.4(RS1):c.589C>T variant is a missense variant encoding the substitution of Arginine with Cystine at amino acid 197. This variant is absent from hemizygous individuals in gnomAD v4.1.0 (PM2_Supporting). The computational predictor REVEL gives a score of 0.99, which is above the ClinGen X-linked IRD VCEP threshold of >0.932 and predicts a damaging effect on RS1 function (PP3_strong). The computational splicing predictor SpliceAI gives a delta score of 0.00 for all predictive splice changes, which is below the ClinGen X-linked IRD VCEP threshold of >0.2 and does not predict that the variant disrupts RS1 splicing. The variant has been reported to segregate with retinal dystrophy through at least 1 meiosis in two unrelated families, each consisting of 2 brothers (PP1; PMID: 29739629, 36377647). Only one family can be counted. At least one 4-year-old proband harboring this variant exhibits a phenotype including appearance of schisis and reduced visual acuity before age 13 years and showing detachment, and showing retinal detachment, which together are highly specific for X-linked retinoschisis (PP4_Moderate). This variant has been reported in at least 4 apparently unrelated probands meeting the PS4 requirements of a male diagnosed with X-linked retinoschisis (PMIDs: 34645606, 29739629, 30652005, 34624300, PS4_Moderate). In summary, this variant is classified as pathogenic for X-linked retinoschisis based on the ClinGen X-linked Inherited Retinal Disease Expert Panel Specifications to the ACMG/AMP Variant Interpretation Guidelines for RS1 Version 1.0.0: PM2_supporting, PP3_strong, PP1, PP4_moderate, and PS4_moderate (date of approval 01/24/2025).