Genotypic and Phenotypic Characterization of Heritable Thoracic Aortic Aneurysm: A Retrospective Single-Center Study

Introduction/Background: Thoracic Aortic Aneurysm (TAA) is a potentially life-threatening condition marked by progressive dilation of the thoracic aorta and risk of rupture. Genetic predisposition plays a relevant role, with about 5% of cases occurring in the context of genetic syndromes and 20% in non-syndromic forms with a positive family history. Connective Tissue Disorders are the primary cause of syndromic TAA, particularly Marfan syndrome, Loeys-Dietz syndrome, vascular Ehlers-Danlos syndrome, and Shprintzen-Goldberg syndrome. Additionally, pathogenic variants in FBN1, ACTA2, PRKG1, MYH11, MYLK, and LOX are implicated in heritable aortic disease. Non-syndromic TAA refers to patients not fulfilling criteria for a defined syndrome, while familial TAA refers to those with thoracic aortic disease and a positive family history. Aim of the study: To provide a genotypic and phenotypic description of a cohort of patients tested for Marfan syndrome and Familial Thoracic Aneurysm, focusing on the clinical indications leading to genetic testing and their correlation with molecular findings. Methods and Material: This retrospective single-center study analyzed 145 patients who underwent genetic testing for Heritable Thoracic Aortic Aneurysm (HTAA) between January 2022 and March 2025 at the Medical Genetics and Clinical Epidemiology Unit of Padua Hospital. Next-generation sequencing of a targeted panel of HTAD-related genes was performed. Identified variants were described by gene, transcript, DNA and protein change, variant type, minor allele frequency (MAF), ACMG classification, and familial data when available. Clinical indications were categorized into four main groups: “Aortic root ± thoracic involvement”, “Non-aortic vessels”, “At least one systemic sign”, and “Other”, further subdivided into “Syndromic suspicion”, “Non-specific sign”, and “Not available”. Results: The cohort included 145 patients (60% male, 40% female; mean age 39 years). The most frequent clinical indications were “Aortic root ± thoracic involvement” and “Other”, especially “Syndromic suspicion”. A total of 45 patients (31%) had at least one variant classified as ACMG Class 3, 4, or 5. The mean age of positive patients was lower (35 years) than negative ones (41 years). FBN1 was the most frequently mutated gene (19%), followed by NOTCH1 (11%). Missense variants were the most common type. Among the 52 total variants, Class 3 (VUS) were the most prevalent (37), followed by Class 4 (7) and Class 5 (8). Class 5 variants were mostly found in patients with “Syndromic suspicion”, while Class 4 variants were associated with “At least one systemic sign”. No Class 4 or 5 variants were observed in patients with “Non-aortic vessels” indication. In patients with double clinical indications, 4 out of 5 individuals with a “Non-specific sign” also had vascular involvement. Segregation analysis was performed in 13 familial cases. Conclusion: This study highlights the clinical and genetic heterogeneity of HTAD. Comprehensive clinical phenotyping proves essential for guiding genetic testing and is associated with a higher diagnostic yield, especially in patients with syndromic or systemic features. A lower yield in older patients with isolated aortic involvement suggests a higher prevalence of sporadic or acquired forms in this group. The high rate of VUS underscores the ongoing challenges in variant interpretation and the importance of familial segregation analysis and multidisciplinary evaluation in HTAD diagnosis and management.