Identification and prenatal genetic testing of pathogenic variants in a case of myoclonus-dystonia syndrome.

内容摘要

Myoclonus-dystonia syndrome (MDS) is a movement disorder syndrome characterized primarily by myoclonus as the core feature. In this study, we reported a case of MDS with myoclonus as the prominent feature, which was accompanied by learning disability and special face. We then used copy number variation sequencing (CNV-seq), whole exome sequencing (WES) and Sanger sequencing to verify the MDS related genes of the patient and his family members. We found that the patient carried a heterozygous mutation of SGCE gene c.731dup (p.Asn244Lysfs*6) related to MDS, which inherited from his father. It was the first reported new mutation at home and abroad. And we confirmed via prenatal diagnosis that his fetus also had a heterozygous mutation of SGCE gene c.731dup (p.Asn244Lysfs*6). In addition, we also found that there was a 1.40 Mb repeat fragment at p23.1 on chromosome 8 of the patient, which partially overlapped with 8p23.1 repeat syndrome. It is speculated that it may be related to the learning disability and special facial phenotype of the patient, and it was a de novo variant. This study not only clarified the etiology of the patient's myoclonus, but also enriched the genetic variation database of SGCE gene by the newly discovered heterozygous heterozygous site of c.731dup (p.Asn244Lysfs*6) of SGCE gene, which was helpful to improve the clinician's awareness of diagnosis of MDS and provide guidance for the patient's fertility. 肌阵挛-肌张力障碍综合征(myoclonus-dystonia syndrome，MDS)是一种以肌阵挛为核心特征的运动异常综合征。本研究报道了1例以肌阵挛为显著特征的MDS患者，其同时伴有学习障碍及特殊面容。通过对患者及其家系成员进行拷贝数变异测序(copy number variation sequencing，CNV-seq)、全外显子组测序(whole-exome sequencing，WES)及Sanger测序验证，发现该患者携带有与MDS相关的SGCE基因c.731dup(p.Asn244Lysfs*6) 杂合变异，为国内外首次报道的新变异。该变异来源于其父亲，且产前诊断结果证实其胎儿也存在SGCE基因c.731dup (p.Asn244Lysfs*6) 杂合变异。此外，患者8号染色体p23.1处存在1.40 Mb重复片段，该片段与8p23.1重复综合征部分重叠，推测可能与患者的学习障碍及特殊面容表型相关，且经家系验证该重复片段为新发变异(其父母均未携带该变异)。本研究不仅明确了患者肌阵挛的病因，而且新发现的SGCE基因c.731dup (p.Asn244Lysfs*6)杂合变异位点丰富了SGCE基因的遗传变异数据库，有助于提升临床医生对MDS的诊断意识。.