STR-PCR在产前诊断胎儿唐氏综合征中的应用

目的:研究通过多重荧光定量PCR诊断胎儿染色体非整倍体用于临床快速产前诊断的可行性。方法:从孕中期羊水中提取胎儿DNA,通过多重荧光定量PCR使用STR对13、18、21号染色体进行非整倍体筛查,筛查结果异常者再进行快速诊断。用PCR诊断的羊水标本同时使用"金标准"染色体核型分析法做对比。结果:34例羊水标本中2例标本由于母血污染严重未行PCR检测,1例标本经PCR及核型分析均失败,29例标本经PCR和核型分析诊断为正常染色体,2例标本经PCR和核型分析诊断为21-三体。结论:通过STR-PCR法使用多重荧光酶联聚合反应探针产前诊断胎儿唐氏综合征是临床快速产前诊断的有效方法之一。     

唐氏综合征产前筛查、诊断预防体系的研究

目的 建立唐氏综合征产前筛查、诊断的预防体系，用于快速、准确诊断唐氏综合征和其他先天畸形，降低出生缺陷。方法 对1110例中孕孕妇外周血血清采用酶联免疫方法检测甲胎蛋白（alpha fetoprotein，AFP）和β—HCG浓度，结合孕妇的年龄、孕周、体重等因素，利用计算机软件计算危险系数，对唐氏综合征高危孕妇做羊水细胞染色体检查，对神经管缺损高危孕妇行B超检查。结果 在1110例孕妇中筛出高危孕妇91例，占筛查总数的8．2％，有36例愿意做进一步产前诊断，发现染色体异常5例，占产前诊断总数的13．9％，其中有1例唐氏综合征（47，XX，＋21），均终止妊娠，检查胎儿染色体核型与产前诊断一致。其中2例神经管缺损高危经B超检查未见异常。结论 建立唐氏综合征产前筛查、诊断综合预防体系对减少先天畸形缺陷儿的出生具有重要意义。     

用荧光原位杂交技术检测唐氏综合征

目的: 探讨用荧光原位杂交技术在检测唐氏综合征中的应用价值。方法: 以Biotin标记的DSCR21q22.3探针与经处理的20例唐氏综合征患者标本外周血中期染色体及其间期细胞核进行原位杂交,统计杂交信号数量。结果: 14例唐氏综合征患者出现3个杂交信号的细胞,染色体和间期细胞核杂交平均出现率分别为98.79％和98.46％,与染色体检测的结果一致;其余染色体核型检测为嵌合体的6例患者,染色体和间期细胞核中3个杂交信号细胞平均出现率分别为75.33％和7 3.50％, 2个杂交信号细胞平均出现率分别为22.67％和21.33％。结论: 荧光原位杂交技术检测唐氏综合征具有快速、敏感度高、信号强、背景低、直观安全等优点,故FISH技术在临床遗传病检测领域中具有重要的应用价值和发展前景。     

双色共变性荧光原位杂交产前诊断胎儿唐氏综合征

目的 探讨双色共变性荧光原位杂交用于非侵入性产前诊断胎儿唐氏综合征的可行性。方法 对11例孕妇外周血中的胎儿有核红细胞进行抗血型糖蛋白磁珠直接标记,再经磁激活细胞分选法富集,以Y和21号染色体专一探针对分离的胎儿有核红细胞行双色共变性荧光原位杂交,预测胎儿21号染色体倍性和性别,并用羊水染色体核型分析结果,验证预测准确性。结果 11例胎儿21号染色体倍性均正常,与羊水染色体核型分析结果相符。其中5例为男性胎儿,男性胎儿有核红细胞数量为9－65个,平均为25个,男性胎儿有核红细胞纯度为1．4％－18．8％;6例为女性胎儿,孕妇外周血中未见男性胎儿有核红细胞;性别预测结果与羊水染色体型分析结果一致。结论 双色共变性荧光原位杂交用于分析胎儿21号染色体倍性及性别,诊断胎儿唐氏综合征准确、可靠。     

非多态性位点多重荧光定量PCR技术在产前诊断胎儿染色体非整倍体异常中的应用

目的 探讨非多态性位点多重荧光定量PCR(QF.PCR)技术快速产前诊断胎儿染色体非整倍体异常的可行性.方法 2006年3月至2007年11月间,收集南京大学医学院附属鼓楼医院早孕期自然流产绒毛组织、中孕期羊水及妊娠晚期的胎儿脐血共63例为研究组.同期60例健康成年人外周血标本(男、女性各30例)作为正常对照组.采用非多态性位点QF-PCR技术检测两组各样本的染色体非整倍体异常情况,以人釉原蛋白基因(AMXY)位点为内参照,根据公式计算剂量系数(DQ)值,DQ值在0.7～1.3之间为正常,>1.3为染色体扩增,<0.7则为染色体存在缺失.当2个以上位点电泳峰与AMXY比值异常时,为性染色体数目异常,即各位点与性染色体峰面积比值均>2.0或<0.7.将QF-PCR的检测结果与染色体核型分析结果进行比较.结果 (1)正常对照组中女性性染色体检测结果为AMX,男性性染色体检测结果为AMX、AMY,与染色体核型分析结果一致.各常染色体DQ值的均值为0.7～1.3,标准差为0.05～0.12.(2)研究组63例中有19例为染色体非整倍体异常,其中13例与核型分析结果一致.与核型分析结果不一致的6例中,1例在18q22.3的CNDP2基因位点表现为三体改变,位于18q12.1的CDH2基因位点表现为正常二倍体,其DQ值为1.28,染色体核型分析为47,XY,+18;5例非多态性位点QF-PCR结果提示有染色体拷贝数异常,而核型分析结果未见异常,其中1例为47,XY,+13,核型分析结果为46,XX;1例为Y染色体缺失,而核型分析结果为46,XY;另外3例中1例为47,XX,+16,2例为47,XX,+13,而核型分析结果均为46,XX.(3)研究组63例中有44例染色体为正常二倍体,其中36例(82%)与核型分析结果一致.与核型分析结果不一致的8例中,1例为培养失败;2例非多态性QF-PCR结果为正常男性,而核型分析结果为正常女性;4例核型分析为多倍体,其中3例核型分析为69,XXX,1例核型分析为92.XXXX;1例核型分析为45,XX,rob(13;21).结论 采用非多态性位点QF-PCR技术进行产前诊断胎儿染色体非整倍体畸形,具有通量高、快速、价廉等特点,有较好的临床应用价值.     

2例胎儿15号小额外标记染色体产前遗传学分析

目的:探讨染色体微阵列分析(CMA)诊断15q小额外标记染色体胎儿的临床价值。方法:获得2例高危孕妇的胎儿羊水或脐血细胞及其双亲外周血细胞,通过CMA和G显带染色体核型分析检测胎儿及其父母的染色体结构。结果:胎儿1:羊水细胞G显带核型分析结果为47,XX,+mar,CMA结果为arr15q11.2(22770421-23288350)×4,其父外周血细胞G显带核型分析结果为47,XY,+mar,母亲外周血染色体核型结果及CMA检测结果未见明显异常。胎儿2:脐血染色体G显带分析结果为47,XX,+mar,CMA结果为arr15q11.2q13.3(22770421-32439524)×4,其父母外周血染色体核型结果及CMA分析结果未见明显异常。结论:通过CMA检测和G显带核型分析结果显示,胎儿1存在15q11.2区域的四拷贝重复变异,经鉴定此携带小额外标记染色体为健康人群多态性。胎儿2存在15q11.2q13.3四拷贝重复小额外标记染色体,确诊为15q11.2q13.3微重复四倍体综合征,出生后可能引起较严重的异常表型。本文对两例15号染色体微重复胎儿进行了产前诊断,明确了胎儿基因型与表型的对应关系,为临床产前诊断和遗传咨询提供可靠的依据。     

荧光定量PCR产前快速诊断唐氏综合征可行性研究

目的建立快速高效的产前诊断唐氏综合征的分子生物学方法。方法分别在21号染色体上选取7个微卫星重复序列(SmallTandemRepeat,STR)(D21S1433,D21S1442,D21S1444,D21S1411,D21S1412,D21S1413,D21S1414)作为遗传标记,利用荧光定量PCR(QF-PCR)扩增技术及片段分析技术,对250例羊水标本进行检测,并与羊水标本染色体核型分析结果进行对比。结果250例羊水标本中,核型分析发现24例21三体,2例性染色体数目异常,24例唐氏综合征样本采用QF-PCR全部检出。224例正常羊水标本中,QF-PCR检出阴性标本223例,1例样本呈假阳性,假阳性率为0.4%,24例21三体标本中,七对引物同时检测诊断阳性率为100%。所有试验结果均在24h内得出。结论QF-PCR作为一种快速、准确、高效的分子生物学方法,对诊断唐氏综合征具有重要意义。     

扩增大肝型磷酸果糖激酶基因对唐氏综合征进行定量基因诊断的研究

目的：扩增位于唐氏综合征关键区域的大肝型磷酸果糖激酶基因（PFKL基因），对唐氏综合征进行定量基因诊断，方法：采用定量PCR－微孔板杂交检测PCR产物量的方法，对26例唐氏综合征患者及278例正常人外周血DNA标本，扩增PFKL基因，扩增片段长度为185bp；另外，将人肌型磷酸糖激酶基因（PFKM基因）作为内参照同时扩增，扩增片段长度为365bp，定量PCR产物用微孔板杂交检测。结果：26例患者（包括1例易位型）PFKM与PFKL扩增产物的OD值比值介于0．40－0．60之间，平均值为0．51；正常人扩增产物的OD值比值介于0．80－1．20之间，平均值为1．12，两者比较差异显著（P＜0．001）。对278例正常人进行同样基因扩增和检测无一例假阳性，所得结果与染色体核型分析结果完全符合。结论：定量PCR－微孔板杂交检测PFKL基因拷贝数的方法，简便，快速，特异，可用于唐氏综合征基因诊断。     

国产13、18、21、X、Y五色探针在产前遗传病诊断中的应用价值

目的 探讨国产21,13,18,X,Y五色探针诊断胎儿最常见染色体疾病的应用价值。方法 采集101例孕周l4~22周孕妇羊水标本,应用国产检测试剂盒21,13,18,X,Y探针进行羊水间期细胞FISH检测,其结果与羊水细胞学染色体培养结果进行对照,计算其灵敏度、特异性、Kappa值等。结果 101例FISH检测全部成功,未见异常99例,发现2例异常核型:21三体嵌合体(47XX,+21/46XX),18三体(47,XY,+18)。并与细胞学染色体培养结果进行对照,所得结果均一致,符合率,灵敏度,特异性,kappa值,均为100%。结论国产五色荧光探针与羊水间期细胞杂交可快速诊断胎儿21,13,18,X和Y染色体数目异常。结果可疑者,要进行常规染色体核型分析。     

多色荧光原位杂交技术的临床检验的应用

目的：探讨多色荧光原位杂交技术在来源不明的额外标记染色体或者衍生染色体中的检测应用;方法：采用多色荧光原位杂交技术、NOR技术以及G显带技术对来源不明的额外标记染色体病例1例以及衍生染色体病例2进行检测;结果：经过检测病例1的染色体片段来源于15号染色体,核型为47,XY,der（5）t（4,5）（q26;q33）,病例2核型为46,XY,inv（7）（p11q14）,＋SMC（15）;结论：多色荧光原位杂交技术与细胞遗传学核型分析相结合,能够有效的对来源不明的标记染色体和衍生染色体进行检测。     

Quantitative real-time PCR technique for rapid prenatal diagnosis of Down syndrome

OBJECTIVES: To develop a reliable and specific technique for rapid prenatal diagnosis of Down syndrome. METHODS: High throughput real-time PCR technique was used to measure the DSCR3 gene dosage of genomic DNAs from uncultured amniocytes of fetuses, lymphocytes of trisomy 21 syndrome patients, and normal people, compared to conventional cytogenetic karyotype analysis. RESULTS: The DSCR3/GAPDH ratio of uncultured amniocytes in trisomy 21 syndrome fetuses to normal fetuses was 1.69 +/- 0.17 to 1.06 +/- 0.14, respectively (p < 0.001); and the DSCR3/GAPDH ratio of lymphocytes in trisomy 21 syndrome children to normal people was 1.67 +/- 0.13 to 0.99 +/- 0.10, respectively (p < 0.001). Real-time PCR technique effectively differentiates the normal fetuses from the trisomy 21 syndrome fetuses; therefore, compared to the results of the conventional cytogenetic karyotype analysis, the DSCR3/GAPDH ratios of trisomy 21 syndrome fetuses are significantly higher than those of normal fetuses. CONCLUSION: Because the DSCR3/GAPDH ratio of trisomy 21 syndrome fetuses is significantly higher than that of normal fetuses, the genomic DNA real-time PCR technique may be a reliable and specific method for the rapid prenatal diagnosis of Down syndrome.     

Detection of trisomy 21 by quantitative fluorescent-polymerase chain reaction in uncultured amniocytes

Prenatal diagnosis of fetal trisomy 21 is usually performed by cytogenetic analysis. This requires lengthy laboratory procedures, high costs and is unsuitable for large-scale screening of pregnant women. Today, trisomy 21 can be rapidly diagnosed within 24 h by molecular analysis of uncultured fetal cells using the semi-quantification of fluorescent PCR products from short tandem repeat (STR) polymorphic markers. The aim of our study was to test a chromosome quantification method on the basis of the analysis of fluorescent PCR products derived from non-polymorphic target genes. Co-amplification of a portion of DSCR1 (Down syndrome Critical Region 1) and the reference gene, CFTR (cystic fibrosis transmembrane regulator) enabled molecular detection of trisomy 21. Our method was successfully tested on a total of 154 amniotic fluids in a blind prospective study. Calculation of the DSCR1/CFTR ratio allowed us to distinguish between 152 normal amniotic fluids (mean ratio 0.99) and 2 amniotic fluids presenting a trisomy 21 status (DSCR1/CFTR ratio of 1.53 and 1.61, respectively). The results obtained by conventional cytogenetic analysis and our quantitative PCR method were concordant in every case. Our gene-based fluorescent PCR approach represents an alternative molecular method for rapid and reliable detection of trisomy 21, which can be helpful in the prenatal diagnosis of women at high risk of fetal trisomy 21.     

染色体13／21α卫得探针用于产前诊断21三体综合征

目的：探讨应用染色体13／21α卫星探荧光原位杂交（FISH）技术行产前论断21三体综合征的价值。方法：选择10例经产前细胞遗传学检查证实为孕正常胎儿孕妇的羊水细胞（对照组）、3例证实为21三体胎儿孕妇的羊水细胞（观察组）,用13／21α卫星探针对未经培养的羊水细胞间期核进行FISH杂交,结果：两组总杂交率分别为36．7％和38．6％,差异无显著性（P＞0．05）。对照组和观察组含4个杂交信号的核平均丰分比分别为36．5％和3．9％,含5个杂交信号的核平均百分比分别为4．0％和36．1％,差异有极显著性（P＜0．01）,含5个信号的百分比＜36．1％可作为21三体综合征的诊断标准。结论：13／21α卫星探针间期FISH用于未培养的羊不细胞可以快速,准确地在产前诊断21三体综合征。     

染色体13/21α卫星探针用于产前诊断21三体综合征

目的探讨应用染色体13/21α卫星探针荧光原位杂交（FISH）技术行产前诊断21三体综合征的价值。方法选择10例经产前细胞遗传学检查证实为孕正常胎儿孕妇的羊水细胞（对照组）、3例证实为孕21三体胎儿孕妇的羊水细胞（观察组）,用13/21α卫星探针对未经培养的羊水细胞间期核进行FISH杂交。结果两组总杂交率分别为36.7%和38.6%,差异无显著性（P>0.05）。对照组和观察组含4个杂交信号的核平均百分比分别为36.5%和3.9%,含5个杂交信号的核平均百分比分别为4.0%和36.1%,差异有极显著性（P<0.01）,含5个信号的核百分比＜36.1%可作为21三体综合征的诊断标准。结论 13/21α卫星探针间期FISH 用于未培养的羊水细胞可以快速、准确地在产前诊断21三体综合征。     

Prenatal diagnosis of maternal uniparental disomy 5 by amniocentesis associated with confined placental mosaicism for trisomy 5 and fetal trisomy 21 in a pregnancy

ObjectiveWe present prenatal diagnosis of maternal uniparental disomy (UPD) 5 by amniocentesis associated with confined placental mosaicism (CPM) for trisomy 5 and fetal trisomy 21 in a pregnancy.Case reportA 45-year-old woman underwent chorionic villus sampling (CVS) at 11 weeks of gestation because of maternal advanced age and an increased nuchal translucency of 4.0 mm in the first-trimester screening. CVS revealed a karyotype of 47,XY,+21[98]/48,XY,+5,+21[25]. Array comparative genomic hybridization (aCGH) analysis on the DNA extracted from chorionic villi revealed arr (5) × 3, arr (21) × 3 compatible with double trisomy 5 and trisomy 21. The woman underwent amniocenteses at 20 weeks and 22 weeks of gestation. Amniocenteses revealed a karyotype of 47,XY,+21. The parental karyotypes were normal. Quantitative fluorescent polymerase chain reaction (QF-PCR) on the DNA extracted from uncultured amniocytes showed trisomy 21 of maternal origin and maternal UPD 5. aCGH and interphase fluorescence in situ hybridization (FISH) on uncultured amniocytes confirmed trisomy 21. Prenatal ultrasound findings were unremarkable. The parents decided to continue the pregnancy, and a 2,198-g male baby was delivered at 38 weeks of gestation with characteristic phenotype of Down syndrome of hypertelorism, epicanthic folds and hypoplastic middle phalanx of the fifth fingers. Cytogenetic analysis of cord blood, umbilical cord and placenta revealed a karyotype of 47,XY,+21. QF-PCR analysis of the DNA extracted from placenta revealed double trisomy 5 and trisomy 21 with maternal gene dosage increase in chromosome 5 and chromosome 21.ConclusionPrenatal diagnosis of CPM for trisomy 5 at CVS can be associated with UPD 5 in the fetus, and UPD 5 causes no specific phenotype.     

Mosaic trisomy 21 at amniocentesis associated with a favorable fetal outcome and perinatal progressive decrease of the trisomy 21 cell line

ObjectiveWe present mosaic trisomy 21 at amniocentesis associated with a favorable fetal outcome and perinatal progressive decrease of the trisomy 21 cell line.Case reportA 33-year-old woman underwent elective amniocentesis at 17 weeks of gestation because of anxiety, and the karyotype of cultured amniocytes was 47,XX,+21[4]/46,XX[13]. In 17 colonies of cultured amniocytes, four colonies had 47,XX,+21, while the other 13 colonies had 46,XX. Simultaneous array comparative genomic hybridization (aCGH) analysis on uncultured amniocytes revealed the result of arr (21) × 3 [0.32] consistent with 32% mosaicism for trisomy 21. Repeat amniocentesis performed at 25 weeks of gestation revealed 47,XX,+21[4]/46,XX[24] with four colonies of 47,XX,+21 and 24 colonies of 46, XX on cultured amniocytes, and arr 21q11.2q22.3 × 2.25 by aCGH, 19.2% mosaicism for trisomy 21 (20/104 cells) by interphase fluorescence in situ hybridization (FISH), and no uniparental disomy (UPD) 21 by quantitative fluorescence polymerase chain reaction (QF-PCR) on uncultured amniocytes. The parental karyotypes were normal, and prenatal ultrasound was unremarkable. A phenotypically normal 2815-g female baby was delivered at 38 weeks of gestation. Cytogenetic analysis on the cord blood, umbilical cord and placenta revealed the karyotype of 47,XX,+21[10]/46,XX[30]. 47,XX,+21[5]/46,XX[35] and 47,XX,+21[38]/46,XX[2], respectively. QF-PCR analysis on the DNA extracted from parental bloods, uncultured amniocytes, cord blood, umbilical cord and placenta confirmed a paternal origin of trisomy 21. When follow-up at age two months, the neonate was phenotypically normal, the peripheral blood had a karyotype of 47,XX,+21[6]/46,XX[34], and no trisomy 21 signals by interphase FISH was found on 100 buccal mucosal cells. When follow-up at age 13 months, the neonate was phenotypically normal, and the peripheral blood had a karyotype of 47,XX,+21[3]/46,XX[37].ConclusionMosaic trisomy 21 at amniocentesis can be a transient and benign condition, and the abnormal trisomy 21 cell line may decrease and disappear after birth.     

Cytogenetic discrepancy between uncultured amniocytes and cultured amniocytes in mosaic trisomy 15 at amniocentesis

ObjectiveWe present mosaic trisomy 15 at amniocentesis.Materials and methodsA 41-year-old woman underwent amniocentesis at 16 weeks of gestation because of an abnormal non-invasive prenatal testing (NIPT) result suspicious of trisomy 15. Amniocentesis revealed a karyotype of 46,XY. Array comparative genomic hybridization (aCGH) on uncultured amniocytes revealed 26% mosaicism for trisomy 15. She was referred for repeat amniocentesis. aCGH, interphase fluorescence in situ hybridization (FISH), quantitative fluorescent polymerase chain reaction (QF-PCR) assays and/or conventional cytogenetic analysis were applied on various cells and tissues including uncultured amniocytes, cultured amniocytes, cord blood, placenta, parental bloods and/or buccal mucosal cells.ResultsRepeat amniocentesis at 21 weeks of gestation revealed a karyotype of 46, XY in cultured amniocytes, and 30% mosaicism for trisomy 15 by aCGH and 32% mosaicism for trisomy 15 by FISH in uncultured amniocytes. Repeat amniocentesis at 29 weeks of gestation revealed a karyotype of 46, XY in cultured amniocytes, and 15% mosaicism for trisomy 15 by aCGH and 7.2% mosaicism for trisomy 15 by FISH in uncultured amniocytes. QF-PCR on cultured amniocytes excluded uniparental disomy (UPD) 15. A phenotypically normal baby was delivered subsequently with a karyotype of 46, XY in cord blood and 2% mosaicism for trisomy 15 by FISH in buccal mucosal cells. The aCGH analysis revealed trisomy 15 in placenta and no genomic imbalance in cord blood. QF-PCR assays determined a maternal origin of trisomy 15 in placenta.ConclusionCytogenetic discrepancy may occur between uncultured and cultured amniocytes in mosaic trisomy 15 at amniocentesis. The cells of trisomy 15 cell line in prenatally detected mosaic trisomy 15 may decrease in number as the fetus grows. Whenever NIPT suspects trisomy 15, a confirmatory amniocentesis should include genetic analysis on both uncultured and cultured amniocytes to exclude mosaic trisomy 15 and maternal UPD 15, especially when the cultured amniocytes have a normal karyotype.     

Cytogenetic discrepancy between uncultured amniocytes and cultured amniocytes in mosaic trisomy 18 at amniocentesis in a pregnancy with a favorable fetal outcome and maternal uniparental disomy 18

ObjectiveWe present prenatal diagnosis of mosaic trisomy 18 in a pregnancy with a favorable fetal outcome and maternal uniparental disomy 18.Case reportA 38-year-old, primigravid woman underwent the first amniocentesis at 16 weeks of gestation because advanced maternal age. Amniocentesis revealed a karyotype of 46,XX [22/22] in cultured amniocytes, and 36% mosaicism for trisomy 18 and a maternally inherited Xp22.31 microdeletion by array comparative genomic hybridization (aCGH) in uncultured amniocytes. The second amniocentesis at 18 weeks of gestation revealed 47,XX,+18 [14]/46,XX [36] in cultured amniocytes and 36% mosaicism for trisomy 18 by multiplex ligation-dependent probe amplification (MLPA) P095 in cultured amniocytes. Prenatal ultrasound was normal. The parents were phenotypically normal. The third amniocentesis at 23 weeks of gestation revealed 47,XX,+18 [3]/46,XX [17] in cultured amniocytes, and in uncultured amniocytes, aCGH revealed 45%–50% mosaicism for trisomy 18, interphase fluorescence in situ hybridization (FISH) revealed 36% (36/100 cells) mosaicism for trisomy 18, and quantitative fluorescent polymerase chain reaction (QF-PCR) showed mosaic maternal uniparental heterodisomy for chromosome 18 and mosaic trisomy 18 of maternal origin. The fourth amniocentesis at 32 weeks of gestation revealed a karyotype of 46,XX [20/20] in cultured amniocytes, and in uncultured amniocytes, aCGH revealed 50%–60% mosaicism for trisomy 18, FISH revealed 21.8% (22/101 cells) mosaicism for trisomy 18, and non-invasive prenatal testing (NIPT) showed chromosome 18 gene dosage increase in the maternal blood. At 34 weeks of gestation, a 1480-g phenotypically normal baby was delivered. The cord blood had 47,XX,+18 [10]/46,XX [30]. The umbilical cord had 47,XX,+18 [4]/46,XX [36]. The placenta had 47,XX,+18 [40/40], and QF-PCR analysis confirmed trisomy 18 of maternal origin. When follow-up at age four months, the neonate was phenotypically normal, FISH analysis on buccal mucosal cells revealed 2% (2/100 cells) mosaicism for trisomy 18, and the peripheral blood had 47,XX,+18 [18]/46,XX [22]. When follow-up at age eight months, the neonate had normal development, the peripheral blood had 47,XX,+18 [15]/46,XX [25], and the buccal mucosal cells showed maternal uniparental heterodisomy for chromosome 18.ConclusionCytogenetic discrepancy may occur between uncultured and cultured amniocytes in mosaic trisomy 18 at amniocentesis. Cultured amniocytes may present progressive decrease in the levels of mosaicism for trisomy 18 as the fetus grows. Mosaic trisomy 18 at amniocentesis can be associated with a favorable outcome.     

Prenatal diagnosis and molecular cytogenetic characterization of mosaicism for a small supernumerary marker chromosome derived from chromosome 16

Objective

We present prenatal diagnosis and molecular cytogenetic characterization of a small supernumerary marker chromosome (sSMC) derived from chromosome 16.