The NM_000330.4(RS1):c.533G>C variant is a missense variant encoding the substitution of Glycine with Alanine at amino acid 178. This variant is absent from hemizygous individuals in gnomAD v4.1.0 (PM2_Supporting). The computational predictor REVEL gives a score of 0.941, 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. Another missense variant in the same codon, c.533G>A, p.Gly178Asp (PMID: 31087526, 12928282, 31149861, 11738458, 9618178) has been classified as pathogenic for X-linked retinoschisis by the ClinGen X-linked IRD VCEP, while no benign missense variants have been identified in this codon. However, the present variant has a lower Grantham’s distance than the comparison variant, so PM5 cannot be met. The variant has been reported to segregate with retinal dystrophy through two affected males of the same family (PP1; PMID: 31087526). This variant has been reported in at least 1 proband meeting the PS4 requirement of a male diagnosed with X-linked retinoschisis (PMID: 31087526), however, PS4_Supporting requires at least 2 unrelated probands, so this criterion was not met. In summary, this variant is classified as likely 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, PP1, and PP3_strong (date of approval 01/24/2025).