The NM_000138 c.4459G>A, is a missense variant in FBN1 predicted to cause a substitution of an Aspartic acid by Asparagine at amino acid 1487 p.(Asp1487Asn). This variant was found in four probands meeting the Ghent criteria (PP4, PS4_strong). The variant segregates with the disease in six affected family members of one proband and three affected family members of another proband (PP1_strong). This variant has been reported three times in ClinVar as likely pathogenic (Variation ID: 549232). It has been reported one time in the literature in a proband with classical Marfan syndrome (PMID: 19293843). This variant is not present in gnomAD v2.1.1 (PM2_sup; https://gnomad.broadinstitute.org/). This variant lies in a critical calcium binding site within a calcium binding EGF domain (PM1). Computational prediction tools and conservation analysis suggest that this variant may impact the protein structure (PP3). The constraint z-score for missense variants affecting FBN1 is 5.06 (PP2). In summary, this variant meets criteria to be classified as pathogenic for Marfan syndrome based on the ACMG/AMP criteria applied, as specified by the ClinGen FBN1 VCEP: PS4, PP1_strong, PM1, PP2, PP3, PP4, PM2_supporting