The NM_00138 c.7165_7166, is a frameshift variant in FBN1 is predicted to result in a premature stop codon at position 2404. It is expected to cause a shift in the reading frame and likely results in an absent or disrupted protein product (PVS1). This variant was found in a proband with a diagnosis of Marfan syndrome, with thoracic aortic aneurysm, skeletal features, which is a highly specific phenotype for Marfan syndrome (internal data) (PP4). This variant, also described as c.7167_7169del2 or p.Leu2389fsX16 using alternate nomenclature, has also been described in three other probands with a clinical diagnosis of Marfan syndrome (PMID 25907466, 17657824, internal data) and in three probands suspected of having Marfan syndrome (PMID 24793577, 14695540, internal data) (PS4). The variant has been identified as a de novo occurrence in an individual with a phenotype consistent with the gene but not highly specific (PM6_Supportive). This variant has been reported 5 times in ClinVar as pathogenic (Variantion ID: 42420). This variant is not present in gnomAD (PM2_sup; https://gnomad.broadinstitute.org/). 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: PVS1, PS4, PM6_Supportive, PM2_Supportive, PP4