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

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.