Identification of a novel FBN1 variant in a pedigree affected with Marfan syndrome / 中华医学遗传学杂志

Objective@#To explore the genetic basis for a pedigree affected with Marfan syndrome (MFS).@*Methods@#Clinical data of the patients was collected.With genomic DNA extracted from peripheral blood samples, potential mutation was detected by targeted exome sequencing.Candidate variants were validated by Sanger sequencing and bioinformatic analysis.@*Results@#Targeted exome sequencing and Sanger sequencing revealed a missense c. 649T>C(p.Trp217Arg) variant in the exon 7 of FBN1 gene, which was unreported previously.Bioinformatics analysis suggested that the variant can cause amino acid replacement and affect the structure and function of fibrillin-1.@*Conclusion@#A novel missense variant of the FBN1 gene was identified, which probably underlies the autosomal dominant MFS in this pedigree.

An atypical case of Noonan syndrome with KRAS mutation diagnosed by targeted exome sequencing

Noonan syndrome (NS) is a genetic disorder caused by autosomal dominant inheritance and is characterized by a distinctive facial appearance, short stature, chest deformity, and congenital heart disease. In individuals with NS, germline mutations have been identified in several genes involved in the RAS/mitogen-activated protein kinase signal transduction pathway. Because of its clinical and genetic heterogeneity, the conventional diagnostic protocol with Sanger sequencing requires a multistep approach. Therefore, molecular genetic diagnosis using targeted exome sequencing (TES) is considered a less expensive and faster method, particularly for patients who do not fulfill the clinical diagnostic criteria of NS. In this case, the patient showed short stature, dysmorphic facial features suggestive of NS, feeding intolerance, cryptorchidism, and intellectual disability in early childhood. At the age of 16, the patient still showed extreme short stature with delayed puberty and characteristic facial features suggestive of NS. Although the patient had no cardiac problems or chest wall deformities, which are commonly present in NS and are major concerns for patients and clinicians, the patient showed several other characteristic clinical features of NS. Considering the possibility of a genetic disorder, including NS, a molecular genetic study with TES was performed. With TES analysis, we detected a pathogenic variant of c.458A > T in KRAS in this patient with atypical NS phenotype and provided appropriate clinical management and genetic counseling. The application of TES enables accurate molecular diagnosis of patients with nonspecific or atypical features in genetic diseases with several responsible genes, such as NS.