Hallopeau-Siemens型营养不良型大疱性表皮松解症一例产前诊断

Prenatal diagnosis of Hallopeau-Siemens recessive dystrophic epidermolysis bullosa

目的鉴定一常染色体隐性遗传营养不良型大疱性表皮松解症家系的突变后,对患者的下一代开展产前诊断。方法首先对患者和患者妻子进行COL7A1基因全部118个外显子的扩增和直接测序。然后从孕15周患者妻子的羊水中提取胎儿的DNA,应用聚合酶链反应(PCR)、DNA直接测序和限制性片段长度多态性(RFLP)的方法来检测突变位点,从而进一步确定该胎儿是否患病。结果发现该患者COL7A1基因的1条等位基因第2号外显子上存在S48P的错义突变,而另1条等位基因第27号外显子上存在3625del11缺失突变,造成编码区阅读框架的移位,最终导致蛋白终止密码(PTC)的产生。患者妻子该基因全序列完全正常。胎儿COL7A1基因的1条等位基因第27号外显子上存在3625del11缺失突变,而另1个第2号外显子序列正常。因此证实该胎儿为携带者,胎儿出生后临床表型正常。结论完成我国首例常染色体隐性遗传的营养不良型大疱性表皮松解症的DNA基础的产前诊断。

Objectives To identify the COL7A1 gene mutation in a recessive dystrophic epidermolysis bullosa （ RDEB ） family, and to perform prenatal diagnosis in the patient＇s offspring, Methods The genomic DNA, obtained from the patient and his wife, was used to screen all 118 exons of the type Ⅶ collagen gene （ COL7A1 ） via polymerase chain reaction （ PCR ） followed by direct DNA sequencing of the PCR products. Fetal DNA was extracted from amniotic fluid of the patient＇s wife at the 15th week of gestation. PCR, direct DNA sequencing and restriction fragment length polymorphisms （ RFLPs ） were performed for prenatal diagnosis. Results The patient in this study was a compound heterozygote for a S48P missense mutation in exon 2 and an 11 base pair deletion （ 3625del 11 ） leading to a premature termination codon （ PTC ） in exon 27, which are a novel combination of COL7AI mutations in RDEB. The COL7A1 genotype of his wife was normal. In the fetus, the same deletion of 11 base pair （ 3625dell 1 ） was found in exon 27, but no mutation was found in exon 2. Thus, the fetus was predicted to be a clinically normal child with a carrier genotype. Seven months later, a clinically unaffected male infant was born and the prediction was confirmed. Conclusion We successfully performed the first DNA-based prenatal diagnosis in China in a family with Hallopeau-Siemens RDEB.