A novel SMAD3 mutation caused multiple aneurysms in a patient without osteoarthritis symptoms

Challenges of Managing Non-rheumatic Aortic Valve Disorder in a Genetically Susceptible Woman

In this case report, we investigated the potential link between SMAD3/transforming growth factor β (TGF-β) pathway dysregulation and aortic valvular disease. We report a middle-aged female, heterozygous for the R18W novel variant of the SMAD3 gene, with a history of an aortic valve disorder and three aortic valve replacements in a span of 15 years. The patient neither has a history of congenital connective tissue disorders nor any known congenital valvular defects. The patient had genetic testing for thoracic aortic aneurysm and dissection (TAAD)/Marfan syndrome/related disorders. She was found to be heterozygous for the p.Arg18Trp (R18W) protein variant of the SMAD3 gene (chromosome position 15:67430416), coding DNA c.52 C>T. Members of the transforming growth factor β (TGF-β) family and their downstream signaling proteins, including SMAD, are important for establishing proper embryogenic development and maintaining adult tissue homeostasis. Investigating the disturbances within the TGF-β signaling pathways may provide insightful knowledge of how genetic factors can cause structural and functional valvular defects.

A Nonsense SMAD3 Mutation in a Girl with Familial Thoracic Aortic Aneurysm and Dissection without Joint Abnormality

INTRODUCTION

Thoracic aortic aneurysms and dissections (TAAD) are rare in children and often associated with underlying genetic disorders accompanied with other systemic manifestations, including connective or osteo-articular tissue diseases.

CASE PRESENTATION

We report the case of a 10-year-old girl with a novel nonsense SMAD3 mutation, p.Glu102X, who presented with familial TAAD without any signs of osteoarthritis. Histological analysis of aorta fragments from the patient with TAAD obtained during surgery revealed elastin degradation and inflammatory infiltration of T cells with dense CD31 + microvessels, which is consistent with previous findings. Interestingly, the family members with the SMAD3 mutation developed IgA nephropathy.

CONCLUSION

Because the TGF-β/Smad signalling pathway plays an important role in the primary pathogenesis of IgA nephropathy and TAAD, we presume that IgA nephropathy could be a novel clinical phenotype of SMAD3 deficiency. Further accumulation of genetically proven cases with SMAD3 deficiency is needed to more accurately characterize phenotypic variability and elucidate a wide spectrum of TGF-β-associated disorders.

The polymorphism of SMAD3 rs1065080 is associated with increased risk for knee osteoarthritis

The mechanism of knee osteoarthritis (OA) is still not clearly elucidated. SMAD3 gene polymorphisms are considered to play a vital role in OA pathogenesis. We thus investigated the relationship of SMAD3 rs1065080 gene polymorphism and susceptibility to knee osteoarthritis in a Chinese Han population. A total of 237 patients and 142 healthy control participants were enrolled in a case-control study. DNA was extracted from peripheral blood samples and genotyped by using the Mass-ARRAY method. Our results revealed that there was a significant difference between patients and healthy controls in the genotype of A and G (p = 0.019); those with a GG genotype had a significant increase in OA risk (OR 2.881, 95% CI 1.993-7.353, p = 0.025). In addition, logistic regression analysis showed that the recessive genetic model decreased OA morbidity (OR 0.648, 95% CI 0.416-0.911, p = 0.046). In conclusion, the GG genotype of rs1065080 was associated with a higher risk of OA and the recessive genetic model decreased the risk of OA.

Isolated aortic dilation without osteoarthritis: a case of SMAD3 mutation

Aneurysm-osteoarthritis syndrome is a recently discovered inherited autosomal dominant connective tissue disease caused by SMAD3 mutations. Aneurysm-osteoarthritis syndrome is responsible for 2% of familial thoracic aortic aneurysms and dissections and is characterised by aneurysms, dissections, and tortuosity throughout the arterial tree in combination with osteoarthritis. Early-onset osteoarthritis is present in almost all patients. We present the case of a non-syndromic young boy with SMAD3 mutation isolated from the dilated aortic root and ascending aorta without osteoarthritis.

A mutation update on the LDS-associated genes TGFB2/3 and SMAD2/3

The Loeys–Dietz syndrome (LDS) is a connective tissue disorder affecting the cardiovascular, skeletal, and ocular system. Most typically, LDS patients present with aortic aneurysms and arterial tortuosity, hypertelorism, and bifid/broad uvula or cleft palate. Initially, mutations in transforming growth factor‐β (TGF‐β) receptors (TGFBR1 and TGFBR2) were described to cause LDS, hereby leading to impaired TGF‐β signaling. More recently, TGF‐β ligands, TGFB2 and TGFB3, as well as intracellular downstream effectors of the TGF‐β pathway, SMAD2 and SMAD3, were shown to be involved in LDS. This emphasizes the role of disturbed TGF‐β signaling in LDS pathogenesis. Since most literature so far has focused on TGFBR1/2, we provide a comprehensive review on the known and some novel TGFB2/3 and SMAD2/3 mutations. For TGFB2 and SMAD3, the clinical manifestations, both of the patients previously described in the literature and our newly reported patients, are summarized in detail. This clearly indicates that LDS concerns a disorder with a broad phenotypical spectrum that is still emerging as more patients will be identified. All mutations described here are present in the corresponding Leiden Open Variant Database.

NGS Technologies as a Turning Point in Rare Disease Research , Diagnosis and Treatment

Approximately 25-50 million Americans, 30 million Europeans, and 8% of the Australian population have a rare disease. Rare diseases are thus a common problem for clinicians and account for enormous healthcare costs worldwide due to the difficulty of establishing a specific diagnosis. In this article, we review the milestones achieved in our understanding of rare diseases since the emergence of next-generation sequencing (NGS) technologies and analyze how these advances have influenced research and diagnosis. The first half of this review describes how NGS has changed diagnostic workflows and provided an unprecedented, simple way of discovering novel disease-associated genes. We focus particularly on metabolic and neurodevelopmental disorders. NGS has enabled cheap and rapid genetic diagnosis, highlighted the relevance of mosaic and de novo mutations, brought to light the wide phenotypic spectrum of most genes, detected digenic inheritance or the presence of more than one rare disease in the same patient, and paved the way for promising new therapies. In the second part of the review, we look at the limitations and challenges of NGS, including determination of variant causality, the loss of variants in coding and non-coding regions, and the detection of somatic mosaicism variants and epigenetic mutations, and discuss how these can be overcome in the near future.