Clinically relevant variants in a large cohort of Indian patients with Marfan syndrome and related disorders identified by next-generation sequencing

Cluster analysis of 100 Marfan patients based on aortic 4D flow MRI and Z-score: insights into disease heterogeneity and stratification of subgroups

OBJECTIVES

4D flow MRI-derived variables from Marfan patients are highly heterogeneous. Our aim was to identify distinct Marfan patient subgroups based on aortic 4D flow MRI and Z-score for stratification of distinct hemodynamic profiles and clinical features by means of hierarchical cluster analysis.

MATERIALS AND METHODS

One hundred Marfan patients underwent baseline aortic 4D flow MRI at 3 T. Z-scores, degree of helical and vortical flow, wall shear stress, flow displacement, and peak velocity were determined in the ascending aorta. Sex, age, BMI, antihypertensive medication, and dural ectasia were recorded. Hierarchical cluster analysis was performed using 4D flow MRI variables and Z-scores as input.

RESULTS

Cluster analysis resulted in three distinct clusters characterized by different Z-scores (mean ± SD); cluster 1: 0.4 ± 1.1 vs. cluster 2: 3.1 ± 1.1 vs. cluster 3: 3.6 ± 1.9. The three clusters delivered differences in helical and vortical flow patterns (global p = 0.003 and p < 0.001, respectively), wall shear stress (0.49 ± 0.11 vs. 0.44 ± 0.12 vs. 0.37 ± 0.09 N/m2, global p < 0.001), flow displacement (0.11 ± 0.05 vs. 0.16 ± 0.08 vs. 0.15 ± 0.07, global p = 0.006), and peak velocity (76.3 ± 9.0 vs. 60.1 ± 7.3 vs. 56.0 ± 7.8 cm/s, global p < 0.001). Patients in cluster 1 and 2 were relevantly younger than in cluster 3 (32.3 ± 13.8 vs. 32.8 ± 12.6 vs. 40.2 ± 15.0 years, all pairwise ∆p < 0.0297).

CONCLUSION

Hierarchical cluster analysis based on aortic 4D flow MRI and Z-score revealed three distinct subgroups of Marfan patients, each characterized by specific hemodynamic profiles and clinical features. Follow-up of our patients is warranted to assess if 4D flow MRI- and Z-score-based stratification can predict future aortic diameter growth and ultimately improve outcomes.

CLINICAL RELEVANCE STATEMENT

A combination of Z-score and 4D flow MRI-derived parameters may help identify subgroups of Marfan patients representing different stages or phenotypes of aortic disease, which require specific management strategies.

KEY POINTS

Four-dimensional (4D) flow MRI-derived variables of Marfan patients are highly heterogeneous across varying Z-scores. Cluster analysis based on 4D flow MRI and Z-score revealed three distinct subgroups of Marfan patients. A combination of Z-score and 4D flow MRI-derived parameters may identify different stages of aortic disease in Marfan patients.

Late diagnosis of Marfan syndrome is associated with unplanned aortic surgery and cardiovascular death

BACKGROUND

Marfan syndrome (MFS) guidelines recommend optimal pharmacologic therapy (OPT) and replacement of the ascending aorta (RAA) at 5.0 cm in diameter to prevent acute type A aortic dissection (ATAAD) and death. The effect of early MFS diagnosis and initiation of therapy on outcomes is not known. Therefore, we sought to evaluate the effect of age at MFS diagnosis and therapy initiation on delayed RAA and death.

METHODS

This retrospective observational cohort study with long-term follow-up included consecutive patients with MFS, pathogenic FBN1 variant, and regular visits to a European Reference Network Center. We considered MFS diagnosis at age ≥21 years late and OPT initiation at age <21 years early. Outcomes were delayed RAA with aneurysm diameter >5.0 cm or ATAAD and death from all causes. We used landmark design starting at age 21 years to determine associations with outcomes.

RESULTS

The study group consisted of 288 patients (45.1% male), including 169 patients with late diagnosis of MFS (58.7%) and 63 with early OPT (21.9%). During mean follow-up of 25 ± 14.7 years, 78 patients had delayed RAA, with 42 operations for ATAAD and 36 for aneurysms ≥5.0 cm. There were 33 deaths, including 11 deaths late after ATAAD. All deaths were cardiovascular. Late diagnosis, but not early OPT, showed univariate association with delayed RAA (P < .001) and death (P = .025). Multivariate Cox regression analysis confirmed late diagnosis as predictor of delayed RAA (hazard ratio, 8.01; 95% confidence interval, 2.52-25.45; P < .001) and death (hazard ratio, 4.68; 95% confidence interval, 1.17-18.80; P = .029).

CONCLUSIONS

Late diagnosis of MFS is associated with delayed surgery and death.

Results of comprehensive genetic testing in patients presenting to a multidisciplinary inherited heart disease clinic in India

OBJECTIVES

This study aims to analyze the results of comprehensive genetic testing in patients presenting to a dedicated multidisciplinary inherited heart disease clinic in India.

METHODS

All patients presenting to our clinic from August 2017 to October 2023 with a suspected inherited heart disease and consenting for genetic testing were included. The probands were grouped into familial cardiomyopathies namely hypertrophic cardiomyopathy (HCM), dilated cardiomyopathy (DCM), arrhythmogenic cardiomyopathy (ACM) and peripartum cardiomyopathy (PPCM), channelopathies namely congenital long QT syndrome (LQTS) and Brugada syndrome (BrS), and heritable connective tissue disorder namely Marfan Syndrome (MFS). Next generation sequencing (NGS) was used, and pre-test and post-test counseling were provided to probands and cascade screening offered to relatives.

RESULTS

Mean age of the subjects (n = 77; 48 probands, 29 relatives) was 43 ± 18 years, 68 % male and 44 % symptomatic, with 36 HCM, 3 DCM, 3 ACM, 1 PPCM, 3 LQTS, 1 BrS and 1 MFS probands. The diagnostic yield of NGS-based genetic testing was 31 %; variants of uncertain significance (VUS) were identified in 54 %; and 15 % were genotype-negative. Twenty-nine relatives from 18 families with HCM (n = 12), DCM (n = 3), ACM (n = 2) and MFS (n = 1) underwent genetic testing. The genotype positive probands/relatives and VUS carriers with strong disease phenotype and/or high risk variant were advised periodic follow-up; the remaining probands/relatives were discharged from further clinical surveillance.

CONCLUSIONS

Genetic testing guides treatment and follow-up of patients with inherited heart diseases and should be carried out in dedicated multidisciplinary clinics with expertise for counseling and cascade screening of family members.

Identification of two novel large deletions in FBN1 gene by next-generation sequencing and multiplex ligation-dependent probe amplification

BACKGROUND

Mutations in fibrillin-1 (FBN1) are known to be associated with Marfan syndrome (MFS), an autosomal dominant connective tissue disorder. Most FBN1 mutations are missense or nonsense mutations. Traditional molecular genetic testing for the FBN1 gene, like Sanger sequencing, may miss disease-causing mutations in the gene's regulatory regions or non-coding sequences, as well as partial or complete gene deletions and duplications.

METHODS

Next-generation sequencing, multiplex ligation-dependent probe amplification and gap PCR were conducted on two MFS patients to screen for disease-causing mutations.

RESULTS

We identified two large deletions in FBN1 from two MFS patients. One patient had a 0.23 Mb deletion (NC_000015.9:g.48550506_48779360del) including 5'UTR-exon6 of FBN1. The other patient harbored a 1416 bp deletion (NC_000015.9:g.48410869_48412284del) affecting the last exon, exon 66, of the FBN1 gene.

CONCLUSION

Our results expanded the number of large FBN1 deletions and highlighted the importance of screening for large deletions in FBN1 in clinical genetic testing, especially for those with the classic MFS phenotype.

Weill-Marchesani syndrome: natural history and genotype-phenotype correlations from 18 news cases and review of literature

BACKGROUND

Weill-Marchesani syndrome (WMS) belongs to the group of acromelic dysplasias, defined by short stature, brachydactyly and joint limitations. WMS is characterised by specific ophthalmological abnormalities, although cardiovascular defects have also been reported. Monoallelic variations in FBN1 are associated with a dominant form of WMS, while biallelic variations in ADAMTS10, ADAMTS17 and LTBP2 are responsible for a recessive form of WMS.

OBJECTIVE

Natural history description of WMS and genotype-phenotype correlation establishment.

MATERIALS AND METHODS

Retrospective multicentre study and literature review.

INCLUSION CRITERIA

clinical diagnosis of WMS with identified pathogenic variants.

RESULTS

61 patients were included: 18 individuals from our cohort and 43 patients from literature. 21 had variants in ADAMTS17, 19 in FBN1, 19 in ADAMTS10 and 2 in LTBP2. All individuals presented with eye anomalies, mainly spherophakia (42/61) and ectopia lentis (39/61). Short stature was present in 73% (from -2.2 to -5.5 SD), 10/61 individuals had valvulopathy. Regarding FBN1 variants, patients with a variant located in transforming growth factor (TGF)-β-binding protein-like domain 5 (TB5) domain were significantly smaller than patients with FBN1 variant outside TB5 domain (p=0.0040).

CONCLUSION

Apart from the ophthalmological findings, which are mandatory for the diagnosis, the phenotype of WMS seems to be more variable than initially described, partially explained by genotype-phenotype correlation.

Targeted Panel Sequencing Identifies an Intronic c.5225-3C>G Variant of the FBN1 Gene Causing Sporadic Marfan Syndrome with Annuloaortic Ectasia

Marfan syndrome (MFS) is a hereditary connective tissue disease whose clinical severity varies widely. Mutations of the FBN1 gene encoding fibrillin-1 are the most common genetic cause of Marfanoid habitus; however, about 10% of MFS patients are unaware of their genetic defects. Herein, we report a Korean patient with MFS and annuloaortic ectasia caused by an intronic c.5225-3C>G variant of the FBN1 gene identified by targeted panel sequencing. The reverse transcription analysis of FBN1 revealed that the intron 43 sequence from positions c.5297-1516 to c.5297-1 was retained at the coding sequence as a consequence of the c.5225-3C>G variant enhancing a cryptic splice acceptor site (c.5297-1518_5297-1517AG) in intron 43. The retained sequence of the part of intron 43 caused the same effect as insertion mutation (NM_000138.5:c.5297_c.5298ins5297-1516_5297-1), resulting in a frameshift mutation resulting in p.Ile1767Trpfs*3. The patient underwent an urgent modified Bentall operation with a 29 mm mechanical valve for annuloaortic ectasia and severe aortic valve regurgitation. This report emphasizes the need for functional investigations into the diagnostic workflows of certain diseases or gene panels with suspected high rates of intronic variants and potential pathogenic effects. Hence, further descriptions of individuals with intronic variants causing alternative splicing expected to have pathogenic effects at different transcript levels are crucial for improving our understanding.

A novel large in-frame FBN1 deletion causes neonatal Marfan syndrome

Neonatal Marfan syndrome (nMFS) is a rare and severe form of Marfan syndrome (MFS) with a poor prognosis, that presents with a highly variable phenotype, particularly regarding skeletal, ocular, and cardiovascular manifestations. Mutations in the fibrillin-1 (FBN1) gene are known as the principal cause of MFS and MFS-related syndromes. Here, we report on a full-term female neonate with postnatal characteristics suggestive of nMFS, including severe cardiovascular disease resulting in cardiorespiratory failure and death by 4 mo of age. We identified a novel large genomic in-frame deletion of FBN1 exons 42-45, c.(5065 + 1_5066 - 1)_(5545 + 1_5546 - 1)del. Large FBN1 in-frame deletions between exons 24 and 53 have been associated with severe MFS. The deletion in our patient differs from the FBN1 region associated with the majority of nMFS cases, exons 24-32.

Understanding Musculoskeletal Disorders Through Next-Generation Sequencing

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An insight into musculoskeletal disorders through advancements in next-generation sequencing (NGS) promises to maximize benefits and improve outcomes through improved genetic diagnosis.

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The primary use of whole exome sequencing (WES) for musculoskeletal disorders is to identify functionally relevant variants.

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The current evidence has shown the superiority of NGS over conventional genotyping for identifying novel and rare genetic variants in patients with musculoskeletal disorders, due to its high throughput and low cost.

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Genes identified in patients with scoliosis, osteoporosis, osteoarthritis, and osteogenesis imperfecta using NGS technologies are listed for further reference.

Clinical profile and outcome of ocular manifestation in Marfans syndrome in India

PURPOSE

Marfan syndrome (MFS) is a genetic disorder associated with considerable morbidity and mortality. Presently, well-documented information on this condition is not available in India.

METHODS

In this retrospective cohort study, we recruited patients with clinically diagnosed MFS who presented to the outpatient department using revised Ghent nosology. We retrieved complete ophthalmic information, including vision, anterior and posterior segments, exported from electronic medical records, and relevant investigations, surgical details, and follow-up data were obtained in a specific, pretested format.

RESULTS

Our cohort consisted of 86 eyes of 43 patients and had a male preponderance. The prevalence was 20.5 per 100,000 individuals. The mean age of the patients was 23.9 years. All eyes were treated either optically with refraction or surgically using lensectomy and vitrectomy with suture supported scleral fixated intraocular lens (IOL), which significantly affected the visual outcome (P = 0.000).

CONCLUSION

Although considered a rare disease, MFS is commonly found in the ophthalmological setting. Refraction and surgery (lensectomy with scleral fixated IOL) may improve the vision significantly.