Clinical relevance of genotype–phenotype correlations beyond vascular events in a cohort study of 1500 Marfan syndrome patients with FBN1 pathogenic variants

Introduction Marfan syndrome (MFS) is a connective tissue disorder in which several systems, including cardiovascular, ophthalmological and skeletal systems, are affected with great phenotypic variability. Although known to be associated with FBN1 mutations, only few genotype-phenotype correlations have been found in probands’ studies only. Objective The clinical variability and unpredictability remain limiting factors for personalized follow-up and effective genetic counseling. The aim of this study was to provide genotype-phenotype correlations in MFS patients with FBN1 mutations. Method In 1575 consecutive MFS probands and relatives from the most comprehensive database worldwide with mutations in the FBN1 gene, we established survival curves and sought genotype-phenotype correlations. Results A risk chart could be established with clinical and genetic data. The aortic risk was greater for males, and probands were more severely affected than relatives as generally agreed. Global survival was 90% at 60 years. However, lifelong aortic event rate (either dissection or surgery) and survival were impacted by the genotype. Premature termination codon variants were not only associated with a shorter life expectancy, a high lifelong risk of aortic event (83%), but also with the highest risk of severe scoliosis (52%) and a lower risk for ectopia lentis (EL) surgery (13%). In-frame variants could be subdivided according to their impact on the cysteine content of fibrillin-1 with a global higher severity for cysteine loss variants and the highest frequency of EL surgery for cysteine addition variants (48%) ( Fig. 1 ). Conclusion This study shows that FBN1 genotype–phenotype correlations exist for both aortic and extra-aortic features. It can be used for optimal risk stratification of patients with a great importance for genetic counseling and personalized medicine. This also provides additional data for the overall understanding of the role of fibrillin-1 in various organs.