Department of Obstetrics and Gynaecology, Pamela Youde Nethersole Eastern Hospital, Chai Wan, Hong Kong, China.
Clinical Genetic Service, Hong Hong Children Hospital, Ngau Tau Kok, Hong Kong, China.
Genes (Basel). 2021 Mar 5;12(3):370. doi: 10.3390/genes12030370.
Tetrasomy 9p (ORPHA:3390) is a rare syndrome, hallmarked by growth retardation; psychomotor delay; mild to moderate intellectual disability; and a spectrum of skeletal, cardiac, renal and urogenital defects. Here we present a Chinese female with good past health who conceived her pregnancy naturally. Non-invasive prenatal testing (NIPT) showed multiple chromosomal aberrations were consistently detected in two sampling times, which included elevation in DNA from chromosome 9p. Amniocentesis was performed and sent for chromosomal microarray, which was normal. Maternal karyotype revealed that mos 47,XX,+dic(9;9)(q21.1;q21.1)(24)/46,XX(9) presents mosaic tetrasomy for the short arm of chromosome 9p and is related to the NIPT results showing elevation in DNA from chromosome 9p. The pregnancy was uneventful, and the patient was delivered at term. Maternal samples were obtained at two different time points after delivery showed the same multiple chromosomal aberrations detected during pregnancy. This is a first report on an unusual case of mosaic isodicentric tetrasomy 9p in a healthy adult with normal intellect. With widespread adoption of NIPT for screening fetal aneuploidy and genome-wide copy number changes, a rise in incidental detection of maternal rare genetic syndrome will bring challenges in our current approach to genetic counselling and prenatal diagnosis.
9p 三体性（ORPHA：3390）是一种罕见的综合征，其特征为生长迟缓；精神运动发育迟缓；轻度至中度智力障碍；以及一系列骨骼、心脏、肾脏和泌尿生殖系统缺陷。在此，我们报告了一位中国女性，她既往健康，自然受孕。无创产前检测（NIPT）在两次采样时间均一致检测到多种染色体异常，包括 9p 染色体 DNA 升高。进行了羊膜穿刺术并进行了染色体微阵列分析，结果正常。母体核型显示 mos 47,XX,+dic(9;9)(q21.1;q21.1)(24)/46,XX(9) 存在 9p 短臂的嵌合体三体性，与 NIPT 结果显示 9p 染色体 DNA 升高有关。妊娠无并发症，足月分娩。分娩后两个不同时间点获得的母体样本显示与怀孕期间检测到的相同的多种染色体异常。这是首例关于智力正常的健康成年人体内罕见的等臂 9p 三体性嵌合体的报告。随着 NIPT 广泛用于筛查胎儿非整倍体和全基因组拷贝数变化，偶然检测到母体罕见遗传综合征的数量增加将给我们目前的遗传咨询和产前诊断方法带来挑战。
