遗传性凝血因子Ⅶ缺乏症——家系基因诊断与产前诊断

Genetic Diagnosis and Prenatal Diagnosis of a Family with Hereditary Coagulation Factor Ⅶ Deficiency

一例经临床和基因诊断为遗传性凝血因子Ⅶ缺乏症的出血症患者,其母亲妊娠后通过产前基因诊断,可避免再次生育相同病症患儿。抽提先证者及家系成员外周血基因组DNA,PCR扩增F7基因所有外显子及侧翼序列,PCR产物经纯化后采用Sanger测序进行基因分析;先证者外周血标本检测到父源性致病突变IVS6-1 C>T及母源性突变c.1198 G>C(p.Val400Leu),前者导致F7基因内含子6经典剪接位点发生改变;c.1198 G>C导致F7基因转录、翻译后位于第400位的氨基酸序列由缬氨酸(Val)改变为亮氨酸(Leu)。先证者母亲再次妊娠后,孕18周超声引导下,无菌抽取羊水进行产前诊断。羊水DNA应用短串联重复序列亲子鉴定方法排除母源性污染,采用和先证者相同的PCR-Sanger测序方法,检测到胎儿携带有母源性F7基因c.1198 G>C(p.Val400Leu)突变,未携带父源性致病突变IVS6-1 C>T。胎儿出生后随访1.5年,凝血功能及生长发育正常。

A patient with hemorrhagic disease was diagnosed as hereditary coagulation factor Ⅶ deficiency by clinical and genetic diagnosis.After the mother of the proband got pregnant,prenatal gene diagnosis was carried out to avoid the fetus bearing the same disease again.Genomic DNA was extracted from peripheral blood of the proband and his family members.All the exons and the flanking sequences of F7 gene were amplified by PCR.PCR products were purified and analyzed by Sanger sequencing.The paternal pathogenic mutation IVS6-1 C>T and the maternal mutation c.1198 G>C(p.Val400 Leu)were detected in the peripheral blood samples of the proband.The former leads to the change of classical splicing site in intron 6 of F7 gene and c.1198 G>C resulted in the change of amino acid sequence at position 400 of F7 gene from Val to Leu.After the proband’s mother was pregnant again,amniotic fluid was aseptically extracted for prenatal diagnosis under the guidance of ultrasound at 18 weeks of gestation.Amniotic fluid DNA was paternally identified by short tandem repeat(STR)to exclude maternal contamination.The same PCR-Sanger sequencing method as the proband was used.It was detected that the fetus carried the maternal F7 gene c.1198 G>C(p.Val400 Leu)mutation and did not carry the paternal pathogenic mutation IVS6-1 C>T.The fetus was followed up for 1.5 years after birth,the coagulation function,growth and development were normal.