Small copy number variations confined to the placenta are extremely rare findings in chorionic villus sampling, nonetheless of great clinical importance. To the best of our knowledge, this is the first reported case of confined placental mosaicism for an intragenic Duchenne muscular dystrophy (DMD) gene deletion. We describe a pregnant woman where confined placental mosaicism for an intragenic DMD deletion was detected. She was referred for a chorionic villus sampling due to an increased risk of trisomy 21 derived from combined first trimester screening. Rapid aneuploidy detection showed a male fetus with normal results for chromosomes 13, 18 and 21. A chromosomal microarray demonstrated a deletion of exons 61–62 in the DMD gene in approximately 50% of the cells. A follow-up analysis on amniotic cells showed a normal result for the DMD gene. Hence, confined placental mosaicism was confirmed. We propose tissue specific fragile sites as a possible theoretical mechanism for the formation of submicroscopic copy number variations and highlight that the finding of DMD deletion mosaicism in a chorionic villus sample might be isolated to the placenta. Therefore, confirmation by amniocentesis is of crucial clinical importance to avoid misdiagnosis of the fetus.

中文翻译：

---

杜兴氏肌营养不良症的局限性胎盘镶嵌术：一例报告

在绒毛膜绒毛取样中，局限于胎盘的小拷贝数变异是极为罕见的发现，尽管如此，其仍具有重要的临床意义。据我们所知，这是第一个报道的因内源性杜氏肌营养不良（DMD）基因缺失而导致的局限性胎盘镶嵌的病例。我们描述了一名孕妇，其中检测到局限性胎盘镶嵌症导致基因内DMD缺失。由于合并了三个月的早孕筛查结果，她因绒毛膜绒毛取样而被转诊，因为它增加了21三体症的风险。快速非整倍性检测显示，雄性胎儿的13号，18号和21号染色体结果正常。染色体微阵列显示DMD基因中约50％的细胞中第61-62号外显子缺失。羊膜细胞的后续分析显示DMD基因正常。因此，证实了局限性胎盘镶嵌术。我们提出组织特定的易碎位点作为形成亚显微拷贝数变异的可能理论机制，并强调绒毛膜绒毛样品中DMD缺失镶嵌的发现可能与胎盘分离。因此，羊膜穿刺术的确诊对避免误诊胎儿至关重要。