Genotype-Guided Risk Stratification of Mitral Valve Surgery in Marfan Syndrome.

Although genotype-based risk stratification for aortic disease has been extensively studied in Marfan syndrome (MFS), mitral valve disease has received less attention despite being a major cardiovascular complication requiring surgery in up to 16% of cases. The authors aimed to evaluate genotype-specific differences in mitral valve disease progression and surgical intervention to inform precision medicine approaches in MFS. This retrospective cohort study included 437 MFS patients with pathogenic FBN1 variants (2006-2024). Variants were classified by molecular mechanism (premature termination codon [PTC] variants vs in-frame variants [IFVs]) and genomic location. Time-to-event cause-specific analysis assessed genotype-specific risks for mitral valve surgery. Among 437 patients, 206 (47.1%) had PTC variants and 231 (52.9%) IFVs. Mitral valve surgery was performed in 38 patients (8.7%) at median age of 25.0 years. Among IFVs, those within the DNCD region (Dominant Negative variants affecting Cysteine residues and in-frame Deletions; exons 26-37 and 44-50) showed markedly higher 30-year cumulative incidence of mitral valve surgery (23.8% [95% CI: 11.7%-35.9%] vs 1.24% [95% CI: 0.0%-2.96%] in other IFVs and 3.20% [95% CI: 0.66%-5.77%] in PTC variants). IFVs within the DNCD region showed the earliest onset of mitral valve surgery in childhood/adolescence, whereas PTC variants demonstrated delayed risk beginning around age 30 years. Cox analysis confirmed IFVs within the DNCD region had highest risk of mitral valve surgery for patients aged ≤30 years (HR: 7.83 vs PTC variants; 95% CI: 3.14-19.57; P < 0.001) with robust discrimination (C-index = 0.725). IFVs within the DNCD region confer the highest risk for mitral valve surgery with distinct age-dependent patterns. These findings enable genotype-guided risk stratification with age-specific surveillance protocols, potentially transforming clinical management in MFS.