Cytogenetical diagnosis in paraffin-embedded fetoplacental tissue using comparative genomic hybridization

Comparative genomic hybridization (CGH) is a FISH-related technique used to assess global chromosomal aberrations in a variety of human tumours. Recently CGH has been applied to cytogenetic analysis of fresh frozen fetoplacental tissues. Here we report the application of CGH to paraffin-embedded placental samples. Ten samples from paraffin-embedded blocks of 6 control placentas and fetoplacental tissue from 10 aneuploidies, and 2 unbalanced aberrations were evaluated. Balanced karyotype profiles were obtained from samples of healthy placentas and all samples from the same placenta appeared to have similar confidence intervals. CGH analysis of four cases of trisomy 21, three cases of trisomy 18, one case of trisomy 13, one case of trisomy 15 and one case of trisomy 7 all showed overrepresentation of the respective trisomic chromosome. The CGH profile was also in accordance with the karyotyping of a case with isochromosome 21. The CGH profile of a case with der (2)t(2;6)(q37.3;q22.2) revealed partial trisomy for chromosome 6 between q21 and q27. CGH may be a useful adjunct in prenatal genetic diagnosis when retrospective diagnosis is needed from archival samples.     

Rapid prenatal diagnosis of trisomy 21 in 5049 consecutive uncultured amniotic fluid samples by fluorescence in situ hybridisation (FISH).

OBJECTIVES: This was a retrospective study on the results of interphase fluorescence in situ hybridization (FISH), performed routinely for chromosome 21 and on ultrasonographic indications for chromosomes 13, 18, X and Y in a series of 5049 amniotic fluid samples. METHODS: Interphase FISH for chromosome 21 was performed in 5049 consecutive amniotic fluid samples for the rapid prenatal diagnosis of Down syndrome. Aneuploidy for four other chromosomes (13, 18, X and Y) was tested following ultrasonographic indications. Karyotypes from standard cytogenetic analysis were compared to the FISH results. RESULTS: Using conventional cytogenetics 3.6% (183/5049) chromosomal anomalies were detected. After exclusion of familial chromosome rearrangements, i.e. balanced autosomal reciprocal or Robertsonian translocations (30/5049) and inversions (19/5049), 2.65% chromosomal anomalies (134/5049) were diagnosed. Of this group 0.18% (9/5049) were chromosomal rearrangements not detectable by FISH and 2.47% (125/5049) were numerical chromosomal anomalies detectable by interphase FISH for chromosomes 13, 18, 21, X and Y. With routine interphase FISH for chromosome 21 and FISH on echographic indication for the other four chromosomes we detected 107/125 of these numerical chromosomal anomalies, i.e. 85.6%. All 70 cases of trisomy 21 were detected by FISH and confirmed with conventional cytogenetics (sensitivity=100%) and there were no false-positive results (specificity=100%). Maternal cell contamination of amniotic fluid samples occurred in 1.27% (64/5049) of samples; 0.26% (13/5049) of these samples were uninformative by FISH due to maternal cell contamination (12/5049) or absence of nuclei in one sample (1/5049). CONCLUSION: In this group of 5049 samples we found that FISH is a reliable technique for the rapid prenatal diagnosis of trisomy 21. The number of uninformative cases due to maternal cell contamination was low. The strategy to perform FISH for chromosome 21 in all samples and only on ultrasonographic indication for the four other chromosomes (13, 18, X and Y) followed by standard cytogenetics is effective.     

De novo monosomy 9p24.3-pter and trisomy 17q24.3-qter characterised by microarray comparative genomic hybridisation in a fetus with an increased nuchal translucency

OBJECTIVES: Increased nuchal translucency (NT) during the first trimester of pregnancy is a useful marker to detect chromosomal abnormalities. Here, we report a prenatal case with molecular cytogenetic characterisation of an abnormal derivative chromosome 9 identified through NT. METHODS: Amniocentesis was performed because of an increased NT (4.4 mm) and showed an abnormal de novo 46,XX,add(9)(p24.3) karyotype. To characterise the origin of the small additional material on 9p, we performed a microarray comparative genomic hybridisation (microarray CGH) using a genomic DNA array providing an average of 1 Mb resolution. RESULTS: Microarray CGH showed a deletion of distal 9p and a trisomy of distal 17q. These results were confirmed by FISH analyses. Microarray CGH provided accurate information on the breakpoint regions and the size of both distal 9p deletion and distal 17q trisomy. The fetus was therefore a carrier of a de novo derivative chromosome 9 arising from a t(9;17)(p24.3;q24.3) translocation and generating a monosomy 9p24.3-pter and a trisomy 17q24.3-qter. CONCLUSION: This case illustrates that microarray CGH is a rapid, powerful and sensitive technology to identify small de novo unbalanced chromosomal abnormalities and can be applied in prenatal diagnosis.     

An efficient protocol for the detection of chromosomal abnormalities in spontaneous miscarriages or foetal deaths

Objective

Characterization of chromosomal abnormalities in 232 spontaneous miscarriages or foetal deaths using both classical and molecular cytogenetics.

Study design

Chromosomal abnormalities are responsible for 40–50% of all early pregnancy losses. Conventional cytogenetics is associated with 10–40% of culture failure. Comparative genomic hybridization (CGH) is a DNA-based technique that screens chromosome imbalances in the whole genome and may overcome this problem, although additional methods are required to distinguish between different ploidies, mosaicisms and maternal cell contamination. For a full characterization of chromosomal aberrations in 232 spontaneous miscarriages or foetal deaths we applied a sequential protocol that uses conventional cytogenetics, plus CGH and touch fluorescence in situ hybridization (Touch FISH).

Results

Successful karyotyping was obtained in 173/232 (74.6%) of the cases, 66/173 (38.2%) of which had an abnormal chromosomal complement. CGH and Touch FISH analyses revealed another 19 abnormal cases in the 63 failures of culture. Overall there were 85/233 (36.6%) cases with an abnormal chromosomal complement, with examples from all three trimesters. Comparing cases, with or without chromosomal abnormalities, no statistical differences were found between women with one or recurrent miscarriages. On the contrary, significant differences were found comparing mean maternal ages or mean gestational ages, in cases with or without chromosomes abnormalities.

Conclusion

Adopting this sequential protocol, chromosomal complement information was available even in cases with culture failure.     

Cytogenetic analysis of trophoblasts by comparative genomic hybridization in embryo-fetal development anomalies

Cytogenetic studies of spontaneous abortions or intrauterine fetal death depend on conventional tissue culturing and karyotyping. This technique has limitations such as culture failure and selective growth of maternal cells. Fluorescent in situ hybridization (FISH) using specific probes permits diagnosis of aneuploidies but is limited to one or a few chromosomal regions. Comparative genomic hybridization (CGH) provides an overview of chromosomal gains and losses in a single hybridization directly from DNA samples. In a prospective study, we analyzed by CGH trophoblast cells from 21 fetuses in cases of spontaneous abortions, intrauterine fetal death or polymalformed syndrome. Six numerical chromosomal abnormalities including one trisomy 7, one trisomy 10, three trisomies 18, one trisomy 21 and one monosomy X have been correctly identified by CGH. One structural abnormality of the long arm of chromosome 1 has been characterized by CGH. One triploidy and two balanced pericentromeric inversions of chromosome 9 have not been identified by CGH. Sexual chromosomal constitutions were concordant by both classical cytogenetic technique and CGH. Contribution of trophoblast analysis by CGH in embryo-fetal development anomalies is discussed.     

Detection of chromosomal abnormalities by comparative genomic hybridization

PURPOSE OF REVIEW: Comparative genomic hybridization (CGH) is a modified in-situ hybridization technique. In this type of analysis, two differentially labeled genomic DNAs (study and reference) are cohybridized to normal metaphase spreads or to microarray. Chromosomal locations of copy number changes in the DNA segments of the study genome are revealed by a variable fluorescence intensity ratio along each target chromosome. Thus, CGH allows detection and mapping of DNA sequence copy differences between two genomes in a single experiment. RECENT FINDINGS: Since its development, comparative genomic hybridization has been applied mostly as a research tool in the field of cancer cytogenetics to identify genetic changes in many previously unknown regions. It is also a powerful tool for detection and identification of unbalanced chromosomal abnormalities in prenatal, postnatal and preimplantation diagnostics. SUMMARY: The development of comparative genomic hybridization and increase in resolution analysis by using the microarray-based technique offer new information on chromosomal pathologies and thus better management of patients.     

Defining the efficiency of fluorescence in situ hybridization on uncultured amniocytes on a retrospective cohort of 27407 prenatal diagnoses

Rapid prenatal detection of selected numerical chromosomal abnormalities by using fluorescence in situ hybridization (FISH) on uncultured amniotic fluid samples was described six years ago. It allows a very rapid identification of selected aneuploidies. We have indexed the results of our 27407 fetal karyotypes obtained by conventional cytogenetics during the last five years, noting the type of chromosomal abnormality and the reasons for prenatal diagnosis. We have also indexed the chromosomal abnormality regarding the prognosis of the chromosomal aberations to evaluate the real impact of a non-diagnosis. Within the population of bad prognosis abnormalities, the percentage of abnormalities with bad prognosis detectable by FISH is 94.6% for advanced maternal age, 85.3% for ultrasonographic anomalies and 86.4% for positive maternal screening. The use of FISH alone on our cohort is not a suitable method to diagnose the chromosomal abnormalities.     

Optimized criteria for using fluorescence in situ hybridization in the prenatal diagnosis of common aneuploidies

OBJECTIVE: To evaluate the medical and economic performance of three strategies for selecting patients eligible for interphase FISH in the prenatal diagnosis of common aneuploidies. METHODS: We evaluated three protocols on the same population that was referred for prenatal diagnosis between June 2001 and December 2006. The number of aneuploidies detected by FISH and the relative cost (reagent and technical staff cost) are reported for each strategy. RESULTS: 2707 women were referred for prenatal diagnosis either because of advanced maternal age over 38 (48%), abnormal maternal serum screening (35%) or prenatal ultrasound anomalies (17%). A total of 4.8% chromosomal anomalies (balanced and unbalanced) were diagnosed after karyotyping. Theoretically, interphase FISH should have detected 79.4% of the unbalanced anomalies. We observed a significant improvement in the trisomy 21 detection by selecting the probes according to the reason for referral. The last protocol adopted, which offers a rapid test to 57% of women undergoing amniocentesis, presents the best aneuploidy detection rate (68% of total aneuploidies, 87% of trisomy 21). CONCLUSION: Selecting probes according to medical criteria patients combined with a technical procedure modification allows medico-economic improvement of interphase FISH in routine diagnosis.     

Use of a DNA method, QF-PCR, in the prenatal diagnosis of fetal aneuploidies

ObjectiveTo provide Canadian health care providers with current information on the use of quantitative fluorescent polymerase chain reaction (QF-PCR) or equivalent technology in the prenatal diagnosis of fetal chromosomal abnormalities.OptionsOver the last few decades, prenatal diagnosis of fetal chromosomal abnormalities has relied on conventional cytogenetic analysis of cultured amniocytes, chorionic villi, or fetal blood. In the last few years, the clinical validity of a newer technique, QF-PCR, to detect the common aneuploidies has been reported by a number of investigators. This technique has the advantage of providing rapid results for the diagnosis or exclusion of aneuploidy in chromosomes 13, 18, 21, X or Y. It is now possible to choose standard chromosome analysis or QF-PCR for the prenatal diagnosis of chromosomal abnormalities, or to perform both tests, depending on the clinical indication for testing. This document reviews the clinical utility of QF-PCR and makes recommendations for its use in the care of Canadian patients.EvidenceMedline and PubMed were searched for articles published in English between January 2000 and December 2010 that presented data on the use of QF-PCR versus standard cytogenetic analysis of prenatal samples. A second search was done to identify publications in English that provided results of cytogenetic analysis performed on prenatal samples for women at an increased risk of fetal aneuploidy because of maternal age, abnormal prenatal screening results, or fetal soft ultrasound markers suggestive of an increased risk of aneuploidy. Publications were included if they provided detailed information on the abnormalities detected, regardless of whether or not rapid aneuploidy screening was undertaken.Results were restricted to systematic reviews, randomized controlled trials, and relevant observational studies. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology assessment-related agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies.ValuesThe quality of evidence was rated using the criteria described in the Report of the Canadian Task Force on Preventive Health Care (Table 1).Benefits, harms, and costsThis guideline promotes the use of a rapid aneuploidy DNA test for women at increased risk of having a pregnancy affected by a common aneuploidy. This will have the benefit of providing rapid and accurate results to women at increased risk of fetal Down syndrome, trisomy 13, trisomy 18, sex chromosome aneuploidy or triploidy. It will also promote better use of laboratory resources and reduce the cost of prenatal diagnosis. However, a small percentage of pregnancies with a potentially clinically significant chromosomal abnormality will remain undetected by QF-PCR but detectable by conventional cytogenetics.Recommendations1. QF-PCR is a reliable method to detect trisomies and should replace conventional cytogenetic analysis whenever prenatal testing is performed solely because of an increased risk of aneuploidy in chromosomes 13, 18, 21, X or Y. As with all tests, pretest counselling should include a discussion of the benefits and limitations of the test. In the initial period of use, education for health care providers will be required. (II-2A)2. Both conventional cytogenetics and QF-PCR should be performed in all cases of prenatal diagnosis referred for a fetal ultrasound abnormality (including an increased nuchal translucency measurement > 3.5 mm) or a familial chromosomal rearrangement. (II-2A)3. Cytogenetic follow-up of QF-PCR findings of trisomy 13 and 21 is recommended to rule out inherited Robertsonian translocations. However, the decision to set up a back-up culture for all cases that would allow for traditional cytogenetic testing if indicated by additional clinical or laboratory information should be made by each centre offering the testing according to the local clinical and laboratory experience and resources. (III-A)4. Other technologies for the rapid detection of aneuploidy may replace QF-PCR if they offer a similar or improved performance for the detection of trisomy 13, 18, 21, and sex chromosome aneuploidy. (III-A)     

Detection of aneuploidy in single cells using comparative genomic hybridization.

The ability of comparative genomic hybridization (CGH) to detect aneuploidy following universal amplification of DNA from a single cell, or a small number of cells, was investigated with a view to preimplantation diagnosis following in vitro fertilization, and prenatal diagnosis using fetal erythroblasts obtained from maternal blood. The DNA obtained from lysed single cells was amplified using degenerate oligonucleotide-primed PCR (DOP-PCR). This product was labelled using nick translation and hybridized together with normal reference genomic DNA. The CGH fluorescent ratio profiles obtained could be used to determine aneuploidy with cut-off thresholds of 0.75 and 1.25. Deviation in the profiles in the heterochromatic regions was reduced by using, as a reference sample, normal genomic DNA that had also undergone DOP-PCR. Single cells known to be trisomic for chromosomes 13, 18 or 21 were analysed using this technique. The resolution of CGH with amplified DNA from a single cell is of the order of 40 Mb, sufficient for the diagnosis of trisomy 21, and possibly segmental aneuploidy of equivalent size. These results, and those of others, demonstrate that diagnosis of chromosomal aneuploidy in single cells is possible using CGH with DOP-PCR amplified DNA.     

Comparative genomic hybridization analysis of spontaneous abortion.

OBJECTIVES: To evaluate the feasibility and superiority of comparative genomic hybridization (CGH) in the genetic analysis of spontaneously aborted tissues. METHODS: 38 conceptuses from early failed pregnancies were studied, of which, 27 samples were fresh and 11 were old. Each sample was divided into two parts, one part for conventional cytogenetic analysis and the other for CGH analysis. RESULTS: All 38 spontaneously aborted tissues were analyzed successfully by the CGH approach, but only 31 samples received results from the cytogenetic karyotype analysis, while 7 other tissues failed to get data due to failure in tissue culturing. Among the specimen successfully analyzed by both approaches, 90% (28 out of 31) obtained identical results, and 14 aneuploidies were found. The only structural chromosome aberration in this series, 46, XY, del(3) (q22-24), was found using the CGH approach, which appeared as a normal male karyotype on the chromosomal metaphase spread. Also, two cases indicated triploidies under cytogenetic analysis but appeared to be normal on the CGH profile. In addition, among the seven samples of tissue culture failure, CGH identified three to be aneuploidies. CONCLUSION: The CGH analysis accurately identifies chromosomal unbalanced abnormalities related to spontaneous abortions with low failure rate.     

CGH in the detection of confined placental mosaicism (CPM) in placentas of abnormal pregnancies

Comparative genomic hybridization (CGH) was applied to samples taken from various sites of placentas originating from complicated pregnancies: 24 with intrauterine growth restriction (IUGR), one with multiple fetal malformation, one with toxemia, one with hydrocephalus and two with undetectable maternal serum alpha-fetoprotein (MSAFP). One of the most common aberrations in the IUGR cases was the addition of a whole or part of the X chromosome. Other aberrations such as additional Y chromosome or of 13(q22) or loss of chromosome 17 also appeared in different cases. In one IUGR case trisomy 8 (in one site) and 47,XXY (in all sites) were detected. In the two cases with undetectable MSAFP monosomy 16 was found. Some of the results were also confirmed by the FISH technique. In all the control cases (six normal and five with aneuploidy) CGH concurred with the known karyotype. Our results demonstrate the usefulness of the CGH technique in the genetic evaluation of fresh and paraffin embedded placentas in problematic pregnancies even when morphology is normal. However, it is very important to take multiple samples from different sites of the placenta.     

Detection of numerical chromosome aberrations by comparative genomic hybridization

At least 50 per cent of all first-trimester spontaneous abortions are cytogenetically abnormal, including trisomy, monosomy X, triploidy, tetraploidy and structural chromosome anomalies. Traditionally, the detection of aneuploidy in fetal tissues is performed by tissue sampling, cell culturing, metaphase spread preparation, and conventional banding analyses. This is a tedious, laborious and time-consuming process, prone to errors due to external contamination, culture failure and selective growth of maternal cells. In the present study, we applied the CGH technique in the detection of numerical chromosome abnormalities in 50 placentae of spontaneously aborted fetuses. CGH detected six different types of trisomy (trisomy 8, 15, 16, 18, 22 and 21), one double trisomy (involving chromosomes 14 and 21), and one monosomy X. Overall, nine samples (18 per cent) harboured numerical chromosome aberrations. Aneuploidy was detected in eight samples by CGH and in six samples by conventional cytogenetic analysis. In only one case, CGH failed to detect a mosaic for trisomy revealed by conventional cytogenetic analysis. The successful application of the CGH technique to the detection of aneuploidy in spontaneous abortions, demonstrates the utility of using this technique to screen prenatally for numerical chromosome abnormalities. Our preliminary data support the application of CGH to the clinical genetics setting, at least as a complementary tool to the traditional cytogenetic techniques.     

Second-trimester prenatal screening for trisomy 21 using biochemical markers: a 7-year experience in one cytogenetic laboratory

BACKGROUND: Screening for trisomy 21 in the second trimester of pregnancy using biochemical markers is an established part of prenatal care in many developed countries. OBJECTIVE: The present study was aimed at determining the incidence of trisomy 21 and other chromosomal abnormalities in women undergoing prenatal chromosome analysis after a second-trimester biochemical screening. RESULTS: A total of 2832 karyotypes were analyzed following a positive second-trimester maternal serum screening (risk > or = 1/250) between 1998 and 2004. Thirty-nine cases of trisomy 21 and 40 other chromosomal abnormalities were detected. The positive predictive value was 1 in 73 karyotypes for trisomy 21 and 1 in 71 for the other chromosomal abnormalities. However, a temporal decline in the detection rate of trisomy 21 was noted, from 1/63 in 1998 to 1/221 in 2004. This change was attributable to an increasing number of pregnant women having first-trimester ultrasound nuchal translucency measurement. CONCLUSION: Given the fact that nuchal translucency measurement combined with first-trimester biochemical marker screening has a positive predictive value of trisomy 21 comparable to that obtained following second-trimester biochemical screening, we should question whether to move trisomy 21 screening by maternal serum markers from the second trimester to the first trimester in conjunction with nuchal translucency measurement. Furthermore, genetic counseling prior to the amniocentesis should discuss the relatively high probability that a chromosomal abnormality other than trisomy 21 may be identified. Copyright (c) 2006 John Wiley & Sons, Ltd.     

Prenatal cytogenetic diagnosis in amniocentesis.

From 1982 to 1990, cytogenetic studies were successfully conducted in 2,975 (96.19%) of the 3,096 pregnant women who underwent amniocentesis. The average maternal age was 33.7 years and the average gestational age was 18.1 weeks. Common indications of amniocentesis included advanced maternal age (AMA) (54.76%), previous fetus with chromosomal aberrations (6.82%) or gross anomalies (5.01%), intrauterine gross anomaly (4.97%) and maternal exposure to drugs or radiation (5.28%). Among the 89 cases (2.99%) with detected chromosomal aberrations, 53 were numeric (31 trisomies, 21 sex chromosome aberrations and one tripoidy) and 36 were structural (six de novo and 30 hereditary structural rearrangement). The incidence of chromosomal aberrations was 2.03% in cases with AMA. While only four of the 143 cases with previous fetal trisomy 21 had recurrence, the recurrent rate was 90.91% in 11 cases with previous fetal chromosomal translocation. Thirty (20.27%) of the 148 cases with abnormal sonograms showed chromosomal aberrations. Certain congenital anomalies are closely associated with cytogenetic changes: duodenal atresia and trisomy 21; cystic hygroma and 45,X; and polyhydramnios and trisomy 18. Only two of the 157 cases with indications of drug or radiation exposure had abnormal cytogenetic studies. Two of the 53 cases with detected numerical aberrations (47,XXY and 47,XXX) and 27 cases with hereditary structural rearrangement elected to continue their pregnancies. All of these babies were delivered without gross anomalies. This study suggests that for prenatal diagnosis. However, complementary measures, such as routine antenatal ultrasound and maternal serum alphafetoprotein, should be added to increase the efficacy of genetic amniocentesis.     

Comparative genomic hybridization-assisted prenatal diagnosis of a de novo inverted duplication of chromosome 10q. A case report

BACKGROUND: Comparative genomic hybridization (CGH) can detect chromosomal imbalance using genomic DNA extracted from tissue without culture and or metaphase spread preparation. It remains a powerful adjunct to conventional karyotyping to help solve clinical cytogenetic cases of intricate unbalanced aberrations. CASE: A 30-year-old, pregnant woman underwent amniocentesis at 16 weeks of gestational age. She had received radioiodine treatment for thyroid disease 4 years earlier and had delivered a healthy infant after treatment. Conventional chromosomal analysis from cultured amniotic fluid cells revealed additional material added to the end of the long arm of 1 chromosome 10. With the aid of CGH, a cytogenetic diagnosis of 46, XY, inv dup(10)(q26q22) was made. CONCLUSION: Though little evidence exists that genetic change on meiosis of oocytes could result from radioiodine treatment, attention should still be paid to pregnant women who have received it. In the case of doubtful results on conventional cytogenetic studies, comparative genomic hybridization could play a role.     

Measurement of nuchal translucency as a single strategy in trisomy 21 screening: should we use any other marker?

OBJECTIVE: To evaluate the role of nuchal translucency thickness as a single marker in screening for trisomy 21 at 10-16 weeks' gestation. METHODS: From December 1996 to October 2001, nuchal translucency was measured in 11,281 consecutive early second trimester fetuses referred to our unit for prenatal care and delivery. Scans were performed by eight experienced ultrasonographers, under strict methodological criteria. RESULTS: Chromosomal abnormalities were found in 118 cases (52 trisomy 21). Using nuchal translucency greater than the 95th centile as a cut-off, the overall detection rate was 71.2% with a specificity of 95.4%, and a positive predictive value of 14%. In the trisomy 21 selected group, detection rate, specificity, and positive predictive value for nuchal translucency were 92.3%, 95.4%, and 8.5%, respectively. The detection rate of trisomy 21 reached 100% when nuchal translucency was measured between 10 and 14 weeks' gestation, maintaining the same specificity. CONCLUSION: Early second trimester nuchal translucency measurement can achieve prenatal detection rates of trisomy 21 greater than 95% with a 5% false-positive rate. With a detection rate so high, the benefits of using additional markers may be less than previously considered. Although maternal age, other sonographic or Doppler markers, and maternal serum biochemistry might play a role in prenatal strategies to detect fetal chromosomal abnormalities, the high detection rate of trisomy 21 fetuses using nuchal translucency as a single parameter suggests that early nuchal translucency measurement between 10 and 14 weeks' gestation can be a simple screening strategy for this condition.     

Prenatal diagnosis and molecular cytogenetic analysis of partial monosomy 10q (10q25.3-->qter) and partial trisomy 18q (18q23-->qter) in a fetus associated with cystic hygroma and ambiguous genitalia

OBJECTIVES: To present the prenatal diagnosis and molecular cytogenetic analysis of a fetus with nuchal cystic hygroma and ambiguous genitalia. CASE AND METHODS: Amniocentesis was performed at 16 weeks' gestation because of the abnormal fetal sonographic finding of a large septated nuchal cystic hygroma. Genetic amniocentesis revealed a terminal deletion in the long arm of chromosome 10. The paternal karyotype was subsequently found to be 46,XY,t(10;18)(q25.3;q23). The maternal karyotype was normal. The pregnancy was terminated. A hydropic fetus was delivered with a septated nuchal cystic hygroma and ambiguous genitalia. Fluorescence in situ hybridization (FISH), microarray-based comparative genomic hybridization (CGH), and polymorphic DNA markers were used to investigate the involved chromosomal segments. RESULTS: FISH study showed absence of the 10q telomeric probe and presence of the 18q telomeric probe in the derivative chromosome 10. Microarray-based CGH analysis showed loss of distal 10q and gain of distal 18q. Polymorphic DNA marker analysis determined the breakpoints. The fetal karyotype was 46,XY,der(10)t(10;18)(q25.3;q23)pat. The chromosome aberration resulted in partial monosomy 10q (10q25.3-->qter) and partial trisomy 18q (18q23-->qter). CONCLUSIONS: The present case provides evidence that partial monosomy 10q (10q25.3-->qter) with partial trisomy 18q (18q23-->qter) can be a genetic cause of fetal cystic hygroma and ambiguous genitalia. Cytogenetic analysis for prenatally detected structural abnormalities may detect unexpected inherited chromosome aberrations.     

An assessment of the use of interphase FISH with chromosome specific probes as an alternative to cytogenetics in prenatal diagnosis

We have assessed the effects that would have been observed if we had changed from standard prenatal diagnosis to interphase fluorescence in situ hybridization (FISH) on our amniocentesis samples. We aimed to estimate the number of cases with aberrations other than chromosomes 13, 18, 21, X and Y, which would not have been detectable by FISH and to assess the potential clinical implications for these cases. In 1687 prenatal diagnoses, 111 cases had abnormal cytogenetic reports (6.5% aneuploidy rate). Out of those 111 cases, 14 had chromosomal abnormalities not detectable by FISH but four of these had major structural abnormalities diagnosed on ultrasound, which would have lead to counselling of a very poor prognosis anyway. In 10 cases without abnormal ultrasound findings, if FISH had been used rather than cytogenetics, it appears that there may have had no detrimental effects on the clinical outcomes of the cases studied. Out of those 10 cases, two pregnancies were terminated because of abnormal cytogenetic results (one was due to maternal age and the second one was due to abnormal biochemical screening) (mosaic 46,XY, /47,XY,+mar and 46,X,del(8)(p21) respectively) and their post-mortem results also did not show any abnormalities. One pregnancy was continued in spite of a de novo chromosomal rearrangement and resulted in an apparently normal live birth. Five cases (including a set of twins) with inherited balanced translocations resulted in four normal live births and one unexplained intrauterine death at 32 weeks' gestation and post-mortem was declined. One case with a paternally derived abnormal chromosome 21, decided to continue the pregnancy and resulted in a normal live birth. The last case in this group resulted in a rhesus related intrauterine death in the second trimester, and although an abnormal chromosome 13 insertion (paternally derived known aberration) there was no abnormality found at post-mortem. Therefore, we suggest that it is reasonable to use FISH as an alternative prenatal diagnosis for indications such as advanced maternal age and abnormal maternal serum biochemical screening when high quality ultrasound scanning is performed, but FISH should only be used as an additional test to conventional cytogenetics for the other indications, especially when abnormalities are found on ultrasound scan.     

两种不同遗传学分析方法用于诊断自然流产组织的比较

目的探讨比较基因组杂交（CGH）技术与绒毛细胞培养染色体核型分析用于自然流产组织遗传学诊断的准确性。方法选择妊娠49—91d的自然流产患者38例,在无菌条件下经宫颈取绒毛,其中难免流产的新鲜组织标本27份,过期流产的陈旧组织标本11份。每份组织标本均采用绒毛细胞培养染色体核型分析,并同时采用CGH技术对全基因组进行分析。结果CGH技术诊断成功率为100％（38／38）,而绒毛细胞培养染色体核型分析诊断成功率为82％（31／38）。两种方法的诊断符合率为90％（28／31）,在3例出现不同诊断结果的病例中,1例绒毛细胞培养染色体核型分析显示染色体核型正常,而CGH技术显示3q^22_q^24缺失;另2例绒毛细胞培养染色体核型分析为3倍体,但CGH技术诊断结果显示正常。在7例绒毛细胞培养失败而仅有CGH技术诊断结果者中,3例为染色体非整倍体异常,另4例正常。结论CGH技术用于诊断自然流产组织是可行的。绒毛细胞培养染色体核型分析比较,CGH技术诊断成功率高,且对非平衡染色体结构重排的诊断有较高的敏感性,可以作为绒毛细胞培养染色体核型分析的补充方法。