The NM_00138 c.5747G>A, is a missense variant in FBN1predicted to cause a substitution of a cysteine by tyrosine at amino acid 1916 (p.Cys1916Tyr). This variant was found in a proband diagnosed with Marfan syndrome (PMID 24793577, PP4). This variant has been reported three times in ClinVar: once as pathogenic, once as likely pathogenic, and once as uncertain significance (Variation ID: 42391). This variant is not present in gnomAD(PM2_sup; https://gnomad.broadinstitute.org/ v2.1.1). This variant affects a cysteine residue in a calcium binding EGF domain. Cysteine residues are believed to be involved in the formation of disulfide bridges which are essential for the protein structure (PM1_strong). Computational prediction tools and conservation analysis suggest that this variant may impact the protein (REVEL: 0.967, PP3). The constraint z-score for missense variants affecting FBN1 is 5.06 (PP2). In summary, this variant meets criteria to be classified as likely pathogenic for Marfan syndrome based on the ACMG/AMP criteria applied, as specified by the ClinGen FBN1 VCEP: PM1_Strong, PM2_Sup, PP2, PP3, PP4.