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Autosomal dominant Marfan syndrome caused by a previously reported recessive FBN1 variant.

ABSTRACT: BACKGROUND:Pathogenic variants in FBN1 cause autosomal dominant Marfan syndrome but can also be found in patients presenting with apparently isolated features of Marfan syndrome. Moreover, several families with autosomal recessive Marfan syndrome caused by pathogenic variants in FBN1 have been described. The aim of this report was to underline the clinical variability that can be associated with the pathogenic variant c.1453C>T, p.(Arg485Cys) in FBN1. METHODS:We provide the clinical details of two autosomal dominant families with this specific FBN1 variant, which was previously associated with autosomal recessive Marfan syndrome. RESULTS:Clinical data of 14 individuals carrying this variant from these two families were collected retrospectively. In both families, the diagnosis of autosomal dominant Marfan syndrome was established based on the characteristics of the variant and the phenotype which includes aortic aneurysms and dissections. Of interest, in one of the families, multiple relatives were diagnosed with early onset abdominal aortic aneurysms. CONCLUSION:In conclusion, FBN1 variant c.1453C>T, p.(Arg485Cys) is a pathogenic variant that can cause autosomal dominant Marfan syndrome characterized by a high degree of clinical variability and apparently isolated early onset familial abdominal aortic aneurysms.

SUBMITTER: Overwater E

PROVIDER: S-EPMC6393656 | biostudies-literature | 2019 Feb

REPOSITORIES: biostudies-literature

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Project description:BackgroundMarfan syndrome (MFS) is a common autosomal dominant inherited disease, and the occurrence rate is around 0.1-0.2‰. The causative variant of FNB1 gene accounts for approximately 70-80% of all MFS cases. In this study, we found a heterozygous c.3217G > T (p.Glu1073*) nonsense variant in the FBN1 gene. This finding extended the variant spectrum of the FBN1 gene and will provide a solution for patients to bear healthy offspring by preimplantation genetic testing or prenatal diagnosis.Case presentationThe patient was treated due to tachycardia during excitement in a hospital. Echocardiography showed dilatation of the ascending aorta and main pulmonary artery, mitral regurgitation (mild), tricuspid regurgitation (mild), and abnormal left ventricular filling. Electrocardiograph showed sinus rhythm. In addition, flutters of shadows in front of his eyes and vitreous opacity were present in the patient. Genomic DNA was extracted from peripheral blood samples from members of the family and 100 unrelated controls. Potential variants were screened out by next-generation sequencing and confirmed by MLPA & Sanger sequencing. Real-time fluorescence quantitative PCR (RT-qPCR) was performed to detect the relative mRNA quantitation in the patient. A heterozygous nonsense variant c.3217G > T of the FBN1 gene, which resulted in p. Glu1073Term, was identified in both patients. Only wild type bases were found in the cDNA sequence of the patient. Real-time fluorogenic quantitative PCR results showed that the relative expression level of FBN1 cDNA in the patient was only about 21% compared to that of normal individuals. This variant c.3217G > T of the FBN1 gene introduces a Stop codon in the cb-EGF12 domain. We speculated that a premature translational-termination codon (PTC) was located in the mRNA and the target mRNA was disintegrated through a process known as nonsense-mediated mRNA decay (NMD), which led to a significant decrease of the fibrillin-1 protein, eventually causing clinical symptoms in the patient.ConclusionsIn this study, we found a heterozygous c.3217G > T (p.Glu1073*) nonsense variant in the FBN1 gene, which eventually led to Marfan syndrome in a Chinese family.

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Autosomal dominant Marfan syndrome caused by a previously reported recessive FBN1 variant.

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