Educational paper. Connective tissue disorders with vascular involvement: from gene to therapy

A novel TGFBR2 mutation causes Loeys-Dietz syndrome in a Chinese infant: A case report

Introduction

Loeys-Dietz syndrome (LDS) is a rare autosomal dominant disorder with extensive connective tissue involvement. The diagnosis of this disease is mainly based on clinical features combined with the detection of pathogenic gene mutations, mainly mutations in the transforming growth factor-beta (TGF-β) signaling pathway.

Methods

The molecular pathogenesis of a LDS syndrome proband and his family members was analyzed using whole exome sequencing and validated using Sanger sequencing. Molecular dynamics simulations and in vitro cell experiments further analyzed the structural changes and functional abnormalities of the variation.

Results

This study describes the case of a 6-month-old infant diagnosed with LDS with typical craniofacial abnormalities, developmental delay, and a dilated aortic sinus (19 mm; Z-score 3.5). Genetic analysis showed the patient carried a novel de novo TGF-β receptor 2 (TGFBR2) mutation (NM_003242: c.1005_1007delGTA (p.Glu335_Tyr336delinsAsp)). Molecular dynamics simulation showed that the TGFBR2 c.1005_1007delGTA mutation changed the protein conformation, making the protein conformation more stable. The p.Glu335_Tyr336delinsAsp mutation significantly reduced TGF-β-induced gene transcription and phosphorylation of SMAD Family Member 2 (SMAD2) in vitro.

Conclusions

Our comprehensive genetic analysis suggested that the p.Glu335_Tyr336delinsAsp variant of TGFBR2 caused aberrant TGF-β signaling and contributed to LDS in the patient.

Loeys-Dietz syndrome and Goldenhar syndrome unveiled together

Haemifacial microsomia is an asymmetrical congenital tissue malformation developed from the first and second branchial arches with or without multi-system involvement. Alternatively recognised as Goldenhar syndrome or oculoauriculovertebral spectrum (OAVS), it is an aetiologically heterogeneous group of disorders showing dominant trends in inheritable form.We present a case of a boy in early childhood with concomitant craniofacial features of craniofacial microsomia with Loeys-Dietz syndrome. He had a unilateral hypoplastic face, asymmetrical ear malformations and multiple preauricular tags with epibulbar dermoid (features suggestive of Goldenhar syndrome). On detailed clinical evaluation, he met Beighton's criteria and was diagnosed with arterial tortuosity. Further molecular testing confirmed the diagnosis of Loeys-Dietz syndrome type II.Loeys-Dietz syndrome is characterised by aortic root enlargement or type A dissection with or without other vascular malformations and facial midline defects. Molecular testing is required to establish the diagnosis because of overlapping features with other connective tissue disorders.

Association of Pectus Excavatum With Ventricular Remodelling and Mitral Valve Abnormalities in Marfan Syndrome

Background: Marfan syndrome (MFS) is an inherited connective tissue disorder. Pectus excavatum (PEX) is common in MFS. The purpose was to evaluate the association of PEX with cardiovascular manifestations of MFS, biventricular size and function. Methods: MFS adults undergoing cardiac MRI were retrospectively evaluated. Exclusion criteria were incomplete cardiac MRI, significant artifacts, co-existent ischaemic or congenital heart disease. Haller Index (HI) ≥3.25 classified patients as PEX positive (PEX+) and PEX negative (PEX-). Cardiac MRI analysis included assessment of mitral valve prolapse (MVP), mitral annular disjunction (MAD), biventricular volumetry and aortic dimensions. Results: 212 MFS patients were included, 76 PEX+ and 136 PEX- (HI 8.3 ± 15.2 vs 2.3 ± 0.5, P < .001). PEX+ were younger (33.4 ± 12.0 vs 38.1 ± 14.3 years, P = .02) and similar in sex distribution (55% vs 63% male, P = .26) compared to PEX-. MVP and MAD were more frequent in PEX+ vs PEX- (43/76 [57%] vs 37/136 [27%], P < .001; 44/76 [58%] vs 50/136[37%], P = .003, respectively). PEX+ had higher right ventricular end-diastolic and end-systolic volumes (RVEDVi 92 ± 17mL/m2 vs 84 ± 22mL/m2, P = .04; RVESVi 44 ± 10 mL/m2 vs 39 ± 14 mL/m2, P = .02), lower RV ejection fraction (RVEF 52 ± 5% vs 55 ± 6%, P = .01) compared to PEX-. Left ventricular (LV) volumes, LVEF and aortic dimensions were similar. Conclusion: MFS adults with PEX have higher frequency of cardiac manifestations including MV abnormalities, increased RV volumes and lower RVEF compared to those without PEX. Awareness of this association is important for all radiologists who interpret aortic CT or MRI, where HI can be easily measured. PEX in MFS may suggest more severe disease expression necessitating careful screening for MV abnormalities and outcomes surveillance.

Neonatal presentation of Loeys-Dietz syndrome: two case reports and review of the literature

Background

Loeys-Dietz syndrome (LDS) is a rare connective tissue disorder characterized by cardiovascular manifestations, especially aortic dilatations and arterial tortuosity, craniofacial and skeletal features, joint laxity or contractures, skin abnormalities, hypotonia and motor delay. Its diagnosis is established by the identification of a pathogenic variant in TGFBR1, TGFBR2, SMAD2, SMAD3, TGFB2 or TGFB3 genes. In newborns and toddlers, vascular complications such as aneurism rupture, aortic dissection, and intracerebral incidents, can occur already in the weeks of life. To avoid these events, it is crucial to precociously identify this condition and to start an apunderwent a surgical procedurepropriate treatment which, depending on the severity of the vascular involvement, might be medical or surgical.

Case presentation

We report two cases of Loeys-Dietz syndrome precociously diagnosed. The first describes a male, born at 38 + 1 weeks of gestation, with hypotonia, joint hypermobility, arachnodactyly, and fingers joint contractures, as well as senile appearance and facial dysmorphisms. In the suspect of a connective tissue disorder, an echocardiography was performed and revealed an aortic root dilatation of 13 mm (Z score + 3). A trio based Whole Exome Sequencing found a novel de novo variant in the TGFBR2 gene. Despite the onset of a low-dose angiotensin receptor blocker therapy, the aneurysm progressed. The second case describes a female, born at 41 + 3 weeks of gestation. During the neonatal examination a cleft palate was noticed, as well as minor dysmorphisms. Since the family history was suspicious for connective tissue disorders, a genetic panel was performed and identified a pathogenetic variant in TGFB3 gene. In this case, the echocardiography revealed no abnormalities.

Conclusions

In addition to our cases, we identified 14 subjects with neonatal LDS in the medical literature. All of them had aortic involvement. Skeletal and face abnormalities, including eyes and palate malformations, were also highly frequent. Overall, 10 subjects required medical therapy to avoid aneurysm progression, and 8 patients underwent surgical procedures.

Benefits of an early diagnosis of LDS are various and imply a potential modification of the natural history of the disease with early interventions on its complications.

Loeys-Dietz syndrome associated with a heterozygous mutation in TGFBR2 in a female infant: A case report

Loeys-Dietz syndrome (LDS) is an unusual hereditary connective tissue disease with no clear standard clinical diagnosis. The present report describes a case of an infant diagnosed with LDS at the age of 2 months and 23 days. To the best of our knowledge, this case represents the youngest reported case of LDS in China. Whole exome sequencing revealed a heterozygous variation, c.1441(exon 6)G>A [p.E481k(p.Glu481Lys) (NM_001024847)], located at chr3:30715708 in the transforming growth factor β receptor 2 gene. The patient underwent systematic rehabilitation and standard high-risk infant follow-up. Currently, the overall development of the patient continues to improve. The patient can walk with assistance, stand up on her feet unaided, exhibits improved optical line of sight and both eyes can move up and down, side to side (left and right) and track moving objects. The parents have been advised that a further echocardiogram should be performed as soon as possible and regular follow-up sessions with a cardiovascular specialist are ongoing. LDS diagnosis was confirmed in the patient based on collective findings of skeletal system changes, ocular hypertelorism, ocular exotropia, micrognathia and high-vaulted palate, in combination with a specific pathogenic gene mutation.

Identification of a novel mutation in FBN1 in a Chinese family with inherited ectopia lentis by targeted NGS

AIMS

To diagnose a Chinese family with inherited ectopia lentis in a genetic method and analyze the genotype-phenotype correlation.

METHODS

The phenotype of each family member was identified by detailed clinical examination. We used targeted next generation sequencing (NGS) to identify mutations in FBN1 in an efficient and accurate way. The mutation in FBN1 was confirmed in all affected family members by Sanger sequencing.

RESULTS

A novel mutation c.385T>C (p.C129R) in FBN1 was identified in the proband by targeted NGS. The mutation was segregated in all affected family members and contributes to specific disease phenotypes. The same mutation was not found in other unaffected relatives and a 100 normal random population by Sanger sequencing.

CONCLUSIONS

Our study reports a novel mutation in FBN1 in a Chinese family and to diagnose this family as Marfan syndrome, we also expand the genotype-phenotype correlation of this disease.

Multifaced Roles of the αvβ3 Integrin in Ehlers-Danlos and Arterial Tortuosity Syndromes' Dermal Fibroblasts

The αvβ3 integrin, an endothelial cells’ receptor-binding fibronectin (FN) in the extracellular matrix (ECM) of blood vessels, regulates ECM remodeling during migration, invasion, angiogenesis, wound healing and inflammation, and is also involved in the epithelial mesenchymal transition. In vitro-grown human control fibroblasts organize a fibrillar network of FN, which is preferentially bound on the entire cell surface to its canonical α5β1 integrin receptor, whereas the αvβ3 integrin is present only in rare patches in focal contacts. We report on the preferential recruitment of the αvβ3 integrin, due to the lack of FN–ECM and its canonical integrin receptor, in dermal fibroblasts from Ehlers–Danlos syndromes (EDS) and arterial tortuosity syndrome (ATS), which are rare multisystem connective tissue disorders. We review our previous findings that unraveled different biological mechanisms elicited by the αvβ3 integrin in fibroblasts derived from patients affected with classical (cEDS), vascular (vEDS), hypermobile EDS (hEDS), hypermobility spectrum disorders (HSD), and ATS. In cEDS and vEDS, respectively, due to defective type V and type III collagens, αvβ3 rescues patients’ fibroblasts from anoikis through a paxillin-p60Src-mediated cross-talk with the EGF receptor. In hEDS and HSD, without a defined molecular basis, the αvβ3 integrin transduces to the ILK-Snail1-axis inducing a fibroblast-to-myofibroblast-transition. In ATS cells, the deficiency of the dehydroascorbic acid transporter GLUT10 leads to redox imbalance, ECM disarray together with the activation of a non-canonical αvβ3 integrin-TGFBRII signaling, involving p125FAK/p60Src/p38MAPK. The characterization of these different biological functions triggered by αvβ3 provides insights into the multifaced nature of this integrin, at least in cultured dermal fibroblasts, offering future perspectives for research in this field.

Management of Scoliosis in Patients With Loeys-Dietz Syndrome

BACKGROUND

Loeys-Dietz syndrome (LDS) is a genetic connective tissue disorder. We sought to determine the incidence of scoliosis in patients with LDS, characterize the spectrum of spinal deformity, determine the results of bracing and surgery, and define surgical complications.

METHODS

Patients were selected from our institution's database of 183 patients with LDS. Imaging measurements were performed for 141 patients whose records permitted spinal evaluation. Deformity changes and complications after intervention were recorded for patients who underwent bracing or surgery, and associations were tested using Student t tests (significance, P<0.05).

RESULTS

Eighty-eight of 141 (62%) patients with LDS had scoliosis, with main thoracic and thoracolumbar curves being most common. Fifteen patients were braced (mean age, 9±3 y) for a mean of 2.3 years. They had a mean postbracing curve progression of 12±21 degrees (5±9 deg./y). There were no significant differences in age, sex, curve type, or prebracing curve magnitude between successfully braced (n=4) and unsuccessfully braced (n=11) patients (P>0.05). Nine patients, (mean age, 12±3 y), underwent 24 surgical procedures (16 growing rod procedures, 8 fusions). Mean curve corrections were 61% for growing rods and 73% for fusions. Associated blood loss for these procedures was 400 mL and 1293 mL, respectively, and normalized blood loss for fusion was 2.34 mL/kg/level. Fifteen of 24 surgical procedures involved complications (63%), including cerebrospinal fluid leaks (n=7) and blood loss >20% of estimated total blood volume (n=11).

CONCLUSIONS

Scoliosis was present in 62% of our sample of LDS patients. Bracing did not halt curves in 11 of 15 patients, whose curves progressed >5 degrees or to >50 degrees by completion of bracing. At latest follow-up, 47% of the braced patients had undergone surgery after prior bracing attempts. The high blood loss associated with these operations is believed to be related to vascular fragility in patients with LDS.

LEVEL OF EVIDENCE

Level IV-retrospective cohort study.

Identification of FBN1 gene mutations in Ukrainian Marfan syndrome patients

Marfan syndrome is an autosomal dominant connective tissue disorder, predominantly affecting the ocular, skeletal and cardiovascular systems. Here, we present the results of the first genetic testing in 40 Ukrainian Marfan (-like) patients and 10 relatives. We applied a targeted next generation sequencing panel comprising FBN1 and 13 thoracic aortic aneurysm genes. We identified 27 causal mutations in FBN1, obtaining a mutation yield of 67·5%. A significant difference in age at aortic surgery between mutation positive and negative patients was observed. Thus, we conclude that genetic testing is important to identify patients at higher risk for developing life-threatening cardiovascular complications.

Heritable thoracic aortic disorders

PURPOSE OF REVIEW

Disease of the wall of the thoracic aorta has many causes: inflammation, infection and atherosclerosis are the most common 'acquired' causes, but even these have genetic predispositions. This article deals with aortic disease due to mutations in specific genes. The conditions can affect tissues and organs other than the aorta (syndromic) or be limited to the aorta (nonsyndromic).

RECENT FINDINGS

A classification scheme based on the gene is emerging, those that affect primarily the extracellular matrix (e.g., FBN1, COL3A1), TGF-β signaling (e.g., TGFBR1, TGFB2), or vascular smooth muscle cell contractility (e.g., ACTA2, MYH11).

SUMMARY

Understanding pathogenesis is driving the development of novel therapies, such as angiotensin receptor blockade, which is in clinical trial. However, recurrent imaging, restriction of exercise, β-adrenergic blockade, and prophylactic surgery remain effective in preventing dissection and sudden death.

Severe aortopathy due to fibulin-4 deficiency: molecular insights, surgical strategy, and a review of the literature

Mutations in the EFEMP2 (alias FBLN4) gene, which encodes the extracellular matrix protein fibulin-4, lead to severe aortopathy with aneurysm formation and vascular tortuosity. The disease phenotype, termed autosomal recessive cutis laxa type 1B (ARCL 1B), is rare among heritable connective tissue diseases but becomes more likely when noting family consanguinity and loose, inelastic skin in the patient. Our patient presented with an intercurrent illness exacerbating upper airway obstruction due to compression from a large aortic aneurysm. Genetic testing eventually revealed the causative mutation. She was initially treated with an angiotensin II receptor blocker and beta-blocker and eventually underwent total thoracic aortic replacement via a two-stage elephant trunk-type procedure. She recovered well and is currently asymptomatic but will require lifetime follow-up due to residual vascular tortuosity and aneurysm risk.

CONCLUSION

Better understanding of the importance of transforming growth factor beta signaling in the pathophysiology of aortopathies such as ARCL 1B has led to targeted medical therapies. Specific surgical techniques can lead to optimal outcomes in these patients.

Loeys-Dietz syndrome in a Southeast Asian Hospital: a case series

Loeys-Dietz syndrome (LDS) is a heritable connective tissue disease in which the activity of the transforming growth factor (TGF) beta signalling pathway is disrupted. The clinical features of LDS represent a clinical continuum that includes LDS type 1, with cutaneous, vascular, skeletal and craniofacial findings, and LDS type 2, with cutaneous, vascular and skeletal findings. We describe five Asian patients with genetically confirmed LDS with mutations in either the TGFBR1 or TGFBR2 gene. Their clinical features were similar to those reported in Caucasian patients. Two patients have novel mutations in TGFBR2. Transcatheter occlusion of patent ductus arteriosus (PDA) was safe and successful in three patients. Treatment with Losartan for aortic root dilatation was well tolerated in our patients, but the outcome is mixed. Among the three patients with follow-up data, aortic root dilatation has improved in two patients but continues to progress in the third patient despite treatment.

CONCLUSION

We describe two novel mutations in TGFBR2 leading to LDS; PDA is common in our patients and can be safely occluded via transcatheter procedure.

Loeys-Dietz syndrome: a primer for diagnosis and management

Loeys-Dietz syndrome is a connective tissue disorder predisposing individuals to aortic and arterial aneurysms. Presenting with a wide spectrum of multisystem involvement, medical management for some individuals is complex. This review of literature and expert opinion aims to provide medical guidelines for care of individuals with Loeys-Dietz syndrome.