TGFβ2基因新突变致4型Loeys-Dietz综合征伴显著骨骼畸形表现一家系研究

A pedigree study of Loeys-Dietz syndrome type 4 with skeletal deformity related to a novel TGFβ2 mutation

目的:Loeys-Dietz综合征为罕见的遗传性结缔组织疾病。分析伴显著骨骼畸形表现的Loeys-Dietz综合征一个家系的临床特征,并鉴定其致病基因突变。方法:收集先证者及家庭成员的临床资料,进行实验室及影像学相关辅助检查,采集家系成员外周血提取DNA,对先证者进行全外显子组测序,确定突变位点,对其他家系成员进行Sanger测序以验证突变位点。结果:先证者男,34岁。双下肢弯曲畸形30余年,体格检查示四肢细长伴扁平足、韧带松弛、脊柱侧弯,超声心动图示主动脉窦部扩张。先证者外周血基因组DNA中TGFβ2基因第1号外显子第220位核苷酸发生杂合错义突变(c.220A>C,p.Thr74Pro)。先证者的姐姐及其1个女儿均存在双下肢弯曲畸形及扁平足等类似临床表现,并检出同一突变基因。该基因突变为新发突变,在ExAC和1000G中均未见报道,致病性预测为有害突变。据此,该家系可诊断为4型Loeys-Dietz综合征。结论:4型Loeys-Dietz综合征由TGFβ2基因突变导致,骨骼畸形是本病的显著特征之一,基因检测有助于早期诊断并与其他结缔组织疾病鉴别诊断。

Objective Loeys-Dietz syndrome is a rare type of hereditary connective tissue disease.This study was aimed to analyze the clinical characteristics and gene mutations in a family of Loeys-Dietz syndrome with skeletal deformity.Methods Clinical data of the proband and family members were collected and biochemical measurements and radiological examinations were conducted.Genomic DNA was extracted from peripheral blood of the family members.Whole-exome sequencing was performed to determine the mutation sites in the proband,and Sanger sequencing was applied to verify the candidate mutation in the other family members.Results The proband is a 34-year-old man with deformities of lower extremities for more than 30 years.Physical examinations showed dolichostenomelia,pes planus,joint laxity and scoliosis.Echocardiography revealed the dilatation of aortic root at the level of the sinuses of Valsalva.A heterozygous missense mutation(c.220A>C,p.Thr74Pro)in exon 1 of TGFβ2 gene was identified in the proband.The same mutation was detected in his sister and niece with similar clinical features such as deformities of lower extremities and pes planus.This novel mutation has not been reported in ExAC or 1000G and was predicted to be deleterious,supporting a diagnosis of Loeys-Dietz syndrome type 4.Conclusions Loeys-Dietz syndrome type 4 is caused by TGFβ2 mutations.Skeletal deformity is one of the distinctive features.Genetic testing is helpful for the early diagnosis and differential diagnosis from other connective tissue diseases.