21羟化酶缺乏症高风险胎儿的产前诊断分析

Prenatal molecular diagnosis of a fetus at high risk for 21-hydroxylyase deficiency

目的对1例21羟化酶缺乏症(21OHD)先证者家系CYP21A2基因缺陷高风险胎儿进行产前分子诊断。方法提取先证者及其父母的外周血DNA,分段扩增CYP21A2基因全长并测序,确定先证者及父母基因型。采用亲子鉴定试验排除母体DNA污染。针对先证者突变位点,扩增羊水DNA并测序。结果测序结果显示先证者存在IVS2-13A>G纯合突变,父母均为携带者。比较STR位点未见羊水DNA受母体DNA污染迹象。胎儿为该突变杂合子,判断胎儿为携带者。培养后羊水检测结果与培养前一致。胎儿娩出后发育良好,证实了产前诊断结果。结论建立了21OHD产前分子诊断方法,并成功应用于1例21OHD高风险胎儿的产前诊断分析。

Objective To perform prenatal molecular diagnosis on a fetus at high risk for 21-hydroxylyase deficiency. Meth- ods Genomic DNA was extracted from peripheral blood of proband and the parents. The coding region of CYP21 A2 gene was amplified in segments by polymerase chain reaction（PCR） to confirm the genotype of proband and the parents. Paternity test was applied to ex- clude the possibility of maternal genomic DNA contamination. After confirming the mutation of the proband, PCR amplification of CYP21A2 gene was carried out by using fetal DNA and the PCR products were sequenced directly. Results The sequencing results showed that a homozygous mutation of IVS2-13A 〉 G was detected in the CYP21A2 gene of the proband and the parents were the 21OHD carriers. By comparing short tandem repeat（STR） sites ,contamination of maternal genomie DNA was not found in fetal DNA. IVS2-13A 〉 G mutation was found in one allele of the fetus by direct sequencing and he was judged as a 21OHD carrier. The detection results of amniotic fluid cell（AFC） before and after culture were identical. The fetus was healthy after birth, consistent with the result of the prenatal molecular diagnosis. Conclusion A method for molecular prenatal diagnosis of 21OHD was established and successfully applied to the prenatal diagnosis of a fetus at high risk for 21-hydroxylyase deficiency.