Thoracic aortic aneurysms leading to type A dissections (TAAD) can be inherited in isolation or in association with genetic syndromes, such as Marfan syndrome and Loeys-Dietz syndrome. When TAAD occurs in the absence of syndromic features, it is inherited in an autosomal dominant manner with decreased penetrance and variable expression, the disease is referred to as familial TAAD. Familial TAAD exhibits significant clinical and genetic heterogeneity. The first genes identified to cause TAAD were FBN1, TGFBR2, and TGFBR1. The identification and characterization of these genes suggested that increased TGF-β signaling plays a role in pathogenesis. The recent discovery that mutations in the vascular smooth muscle cell (SMC)-specific β-myosin (MYH11) and α-actin (ACTA2) can also cause this disorder has focused attention on the importance of the maintenance of SMC contractile function in preserving aortic structure and preventing TAAD.

Dianna Milewicz and colleagues report the identification of loss-of-function mutations in TGFB2 in individuals with familial thoracic aortic aneurysm and acute aortic dissection associated with mild systemic features of the Marfan syndrome. A predisposition for thoracic aortic aneurysms leading to acute aortic dissections can be inherited in families in an autosomal dominant manner. Genome-wide linkage analysis of two large unrelated families with thoracic aortic disease followed by whole-exome sequencing of affected relatives identified causative mutations in TGFB2. These mutations—a frameshift mutation in exon 6 and a nonsense mutation in exon 4—segregated with disease with a combined logarithm of odds (LOD) score of 7.7. Sanger sequencing of 276 probands from families with inherited thoracic aortic disease identified 2 additional TGFB2 mutations. TGFB2 encodes transforming growth factor (TGF)-β2, and the mutations are predicted to cause haploinsufficiency for TGFB2; however, aortic tissue from cases paradoxically shows increased TGF-β2 expression and immunostaining. Thus, haploinsufficiency for TGFB2 predisposes to thoracic aortic disease, suggesting that the initial pathway driving disease is decreased cellular TGF-β2 levels leading to a secondary increase in TGF-β2 production in the diseased aorta.

Marfan syndrome (MFS) is a heritable disorder of the connective tissue with a prevalence of ≈1 in 3000 to 5000 individuals. The condition is inherited in an autosomal dominant manner with complete penetrance but demonstrates variable expression with significant intra- and interfamilial variation. Approximately 25% of patients do not have a family history and represent sporadic, new mutations for the condition. The cardinal features of MFS involve the cardiovascular, ocular, and skeletal systems. The most life-threatening complication of MFS is thoracic aortic aneurysms leading to aortic dissection, rupture, or both. This article focuses on medical and surgical treatment of aortic disease in patients with MFS and addresses the treatment of aortic disease in children and pregnant women with the condition. The most common cardiovascular complication in patients with MFS is progressive aortic root enlargement initially occurring at the sinuses of Valsalva. Ascending aortic aneurysm can precipitate acute type A aortic dissection, aortic rupture, aortic regurgitation (AR), or all 3, and these complications were the primary cause of death before the advent of successful preventive therapies. Treatment of the aorta consists of regular imaging to detect and quantify progression of aortic dilation, β-adrenergic receptor antagonist therapy, and prophylactic aortic repair when the dilation reaches a sufficient size to threaten dissection or cause AR. Before the era of open-heart surgery, the majority of patients with MFS died prematurely of rupture of the aorta, with an average life expectancy of 45 years.1 The success of current medical and surgical treatment of aortic disease in MFS has substantially improved the average life expectancy, extending it up to 70 years.2,3 Cardiovascular manifestations in MFS also include valvular disease involving the mitral valve, aortic valve, or both. Mitral valve prolapse is the most prevalent valvular abnormality, affecting 35% to 100% of patients.4 Mitral …

Background— A genetic predisposition for progressive enlargement of thoracic aortic aneurysms leading to type A dissection (TAAD) is inherited in an autosomal-dominant manner in up to 19% of patients, and a number of chromosomal loci have been identified for the condition. Having mapped a TAAD locus to 3p24–25, we sequenced the gene for transforming growth factor-β receptor type II ( TGFBR2 ) to determine whether mutations in this gene resulted in familial TAAD. Methods and Results— We sequenced all 8 coding exons of TGFBR2 by using genomic DNA from 80 unrelated familial TAAD cases. We found TGFBR2 mutations in 4 unrelated families with familial TAAD who did not have Marfan syndrome. Affected family members also had descending aortic disease and aneurysms of other arteries. Strikingly, all 4 mutations affected an arginine residue at position 460 in the intracellular domain, suggesting a mutation “hot spot” for familial TAAD. Despite identical mutations in the families, assessment of linked polymorphisms suggested that these families were not distantly related. Structural analysis of the TGFBR2 serine/threonine kinase domain revealed that R460 is strategically located within a highly conserved region of this domain and that the amino acid substitutions resulting from these mutations will interfere with the receptor’s ability to transduce signals. Conclusion— Germline TGFBR2 mutations are responsible for the inherited predisposition to familial TAAD in 5% of these cases. Our results have broad implications for understanding the role of TGF-β signaling in the pathophysiology of TAAD.