Cardiovascular involvement and prognosis in Loeys-Dietz syndrome

BACKGROUND

Loeys-Dietz syndrome (LDS) is an inherited connective tissue disorder associated with aortic root enlargement and risk of thoracic aortic dissection (AD). Genetic examination is essential for diagnosis.

AIMS

The study aimed at analysis of clinical data on cardiovascular involvement and management of LDS patients.

METHODS

The study included carriers of LDS-associated genetic variants, identified between 2012 and 2022. Assessment of cardiovascular involvement was based on echocardiography and computed tomography angiography with quantitative assessment of arterial tortuosity. Involvement of other systems was also evaluated. We noted major cardiovascular events, including aortic events, defined as AD, elective aortic surgery, or otherwise unexplained sudden death.

RESULTS

Thirty-four patients from 15 families were included, and five identified variants were novel. Probands' mean age was 41 years. Cardiovascular abnormalities, aortic involvement, aortic tortuosity, and tortuosity of cervical arteries were present in 79%, 71%, 68%, and 100% of carriers, respectively. First aortic events (9 A-type AD, 6 elective thoracic aortic surgeries, and one sudden death) occurred in 16 (47%) patients at a median age of 35 years. The youngest age at AD was 16 years, and 7 years for elective aneurysm repair. Second and third aortic events occurred in 9 and 4 patients, respectively. Eight patients (24%) experienced other major cardiovascular events. Aortic event-free survival was shorter in the presence of skin striae (P = 0.03), tended to be shorter in the presence of Marfanoid features (P = 0.06), and longer with TGFB2 variants (P = 0.06).

CONCLUSIONS

LDS is associated with high burden of cardiovascular complications at a young age.

Frail Silk: Is the Hughes-Stovin Syndrome a Behçet Syndrome Subtype with Aneurysm-Involved Gene Variants?

Hughes-Stovin syndrome is a rare disease characterized by thrombophlebitis and multiple pulmonary and/or bronchial aneurysms. The etiology and pathogenesis of HSS are incompletely known. The current consensus is that vasculitis underlies the pathogenic process, and pulmonary thrombosis follows arterial wall inflammation. As such, Hughes-Stovin syndrome may belong to the vascular cluster with lung involvement of Behçet syndrome, although oral aphtae, arthritis, and uveitis are rarely found. Behçet syndrome is a multifactorial polygenic disease with genetic, epigenetic, environmental, and mostly immunological contributors. The different Behçet syndrome phenotypes are presumably based upon different genetic determinants involving more than one pathogenic pathway. Hughes-Stovin syndrome may have common pathways with fibromuscular dysplasias and other diseases evolving with vascular aneurysms. We describe a Hughes-Stovin syndrome case fulfilling the Behçet syndrome criteria. A MYLK variant of unknown significance was detected, along with other heterozygous mutations in genes that may impact angiogenesis pathways. We discuss the possible involvement of these genetic findings, as well as other potential common determinants of Behçet/Hughes-Stovin syndrome and aneurysms in vascular Behçet syndrome. Recent advances in diagnostic techniques, including genetic testing, could help diagnose a specific Behçet syndrome subtype and other associated conditions to personalize the disease management.

Whole-Exome Sequencing Identified Genes Responsible for Thoracic Aortic Aneurysms and Dissections in three Chinese Families

Thoracic aortic aneurysms and dissections are precarious conditions that often cannot be diagnosed with fatal outcomes. Over the last few years, pathogenic variants in numerous genes have been identified that predispose to heritable presentations of TAAD. An evidence-based strategy for the selection of genes to test in familial TAAD helps inform family screening and intervention to prevent life-threatening events. Using whole-exome sequencing, four members of three unrelated families clinically diagnosed with TAAD were used to identify the genetic origin of the disorder. Variant evaluation was carried out to detect the pathogenic mutation. Our studies suggest that mutations of COL3A1 and ACTA2 are responsible for familial TAAD. In addition, we highlight FBLN5, FBN1, SLC2A10, FBN2, and NOTCH1 as candidate genes. Future studies of crosstalk among the pathways may provide us a step toward understanding the pathogenic mechanism. This finding indicates the necessity of obtaining family medical history and screening of extended relatives of patients with TAAD for the early identification and treatment of TAAD.

Coincidence of Andersen-Tawil syndrome and Marfan syndrome: A case report

We report on a 44-year-old woman with coincidence of two genetic disorders: Andersen-Tawil syndrome and Marfan syndrome. In both, life-threatening arrhythmias could occur. A 44-year-old woman presented acute ascending aortic dissection with aortic arch involvement and chronic thoracic descending and abdominal aortic dissection. Clinical and genetic examination confirmed Marfan syndrome (MFS) diagnosis. Due to repolarization disorder in ECG and premature ventricular contractions in Holter ECG, the sequencing data were analyzed again and mutation in KCNJ2 gene was identified. The case showed that coincidence of Andersen-Tawil syndrome (ATS) and MFS did not provoke life-threatening arrhythmias. Complication was rather caused by expression of FBN1 mutation.

IL-6 regulates extracellular matrix remodeling associated with aortic dilation in a fibrillin-1 hypomorphic mgR/mgR mouse model of severe Marfan syndrome

Background

Development of thoracic aortic aneurysms is the most significant clinical phenotype in patients with Marfan syndrome. An inflammatory response has been described in advanced stages of the disease. Because the hallmark of vascular inflammation is local interleukin‐6 (IL‐6) secretion, we explored the role of this proinflammatory cytokine in the formation of aortic aneurysms and rupture in hypomorphic fibrillin‐deficient mice (mgR/mgR).

Methods and Results

MgR/mgR mice developed ascending aortic aneurysms with significant dilation of the ascending aorta by 12 weeks (2.7±0.1 and 1.3±0.1 for mgR/mgR versus wild‐type mice, respectively; P<0.001). IL‐6 signaling was increased in mgR/mgR aortas measured by increases in IL‐6 and SOCS3 mRNA transcripts (P<0.05) and in cytokine secretion of IL‐6, MCP‐1, and GM‐CSF (P<0.05). To investigate the role of IL‐6 signaling, we generated mgR homozygous mice with IL‐6 deficiency (DKO). The extracellular matrix of mgR/mgR mice showed significant disruption of elastin and the presence of dysregulated collagen deposition in the medial‐adventitial border by second harmonic generation multiphoton autofluorescence microscopy. DKO mice exhibited less elastin and collagen degeneration than mgR/mgR mice, which was associated with decreased activity of matrix metalloproteinase‐9 and had significantly reduced aortic dilation (1.0±0.1 versus 1.6±0.2 mm change from baseline, DKO versus mgR/mgR, P<0.05) that did not affect rupture and survival.

Conclusion

Activation of IL‐6‐STAT3 signaling contributes to aneurysmal dilation in mgR/mgR mice through increased MMP‐9 activity, aggravating extracellular matrix degradation.

TGFBR2 mutations alter smooth muscle cell phenotype and predispose to thoracic aortic aneurysms and dissections

AIMS

Transforming growth factor-β (TGF-β) signaling is critical for the differentiation of smooth muscle cells (SMCs) into quiescent cells expressing a full repertoire of contractile proteins. Heterozygous mutations in TGF-β receptor type II (TGFBR2) disrupt TGF-β signaling and lead to genetic conditions that predispose to thoracic aortic aneurysms and dissections (TAADs). The aim of this study is to determine the molecular mechanism by which TGFBR2 mutations cause TAADs.

METHODS AND RESULTS

Using aortic SMCs explanted from patients with TGFBR2 mutations, we show decreased expression of SMC contractile proteins compared with controls. Exposure to TGF-β1 fails to increase expression of contractile genes in mutant SMCs, whereas control cells further increase expression of these genes. Analysis of fixed and frozen aortas from patients with TGFBR2 mutations confirms decreased in vivo expression of contractile proteins relative to unaffected aortas. Fibroblasts explanted from patients with TGFBR2 mutations fail to transform into mature myofibroblasts with TGF-β1 stimulation as assessed by expression of contractile proteins.

CONCLUSIONS

These data support the conclusion that heterozygous TGFBR2 mutations lead to decreased expression of SMC contractile protein in both SMCs and myofibroblasts. The failure of TGFBR2-mutant SMCs to fully express SMC contractile proteins predicts defective contractile function in these cells and aligns with a hypothesis that defective SMC contractile function contributes to the pathogenesis of TAAD.