Additional information from array comparative genomic hybridization technology over conventional karyotyping in prenatal diagnosis: a systematic review and meta-analysis.

OBJECTIVE: Array comparative genomic hybridization (CGH) is transforming clinical cytogenetics with its ability to interrogate the human genome at increasingly high resolution. The aim of this study was to determine whether array CGH testing in the prenatal population provides diagnostic information over conventional karyotyping. METHODS: MEDLINE (1970 to December 2009), EMBASE (1980 to December 2009) and CINAHL (1982 to December 2009) databases were searched electronically. Studies were selected if array CGH was used on prenatal samples or if array CGH was used on postnatal samples following termination of pregnancy for structural abnormalities that were detected on an ultrasound scan. Of the 135 potential articles, 10 were included in this systematic review and eight were included in the meta-analysis. The pooled rate of extra information detected by array CGH when the prenatal karyotype was normal was meta-analyzed using a random-effects model. The pooled rate of receiving an array CGH result of unknown significance was also meta-analyzed. RESULTS: Array CGH detected 3.6% (95% CI, 1.5-8.5) additional genomic imbalances when conventional karyo-typing was 'normal', regardless of referral indication. This increased to 5.2% (95% CI, 1.9-13.9) more than karyotyping when the referral indication was a structural malformation on ultrasound. CONCLUSIONS: There appears to be an increased detection rate of chromosomal imbalances, compared with conventional karyotyping, when array CGH techniques are employed in the prenatal population. However, some are copy number imbalances that are not clinically significant. This carries implications for prenatal counseling and maternal anxiety.

Rapid prenatal diagnosis of common trisomies: discordant results between QF-PCR analysis and karyotype analysis on long-term culture for a case of trisomy 18 detected in CVS.

OBJECTIVES: QF-PCR analysis can be used as a rapid test to diagnose primary trisomy in prenatal samples. Mosaicism in CVS detected by QF-PCR has previously been reported; however, no case has so far been reported in which the QF-PCR result was completely discrepant to that of the karyotype analysis from a long-term culture. METHODS: A CVS, referred because of a high serum screening risk of 1:10 for Down Syndrome and 1:110 for Edwards Syndrome, was tested by QF-PCR analysis and chromosome analysis of cultured cells. Subsequent analyses were carried out on a follow-up amniotic fluid sample and foetal tissue samples. RESULTS: Conflicting results were obtained between QF-PCR analysis on two independent fronds from the chorionic villi and chromosome analysis on cultured CVS. Cytogenetic and molecular analysis on a subsequent amniotic fluid sample indicated trisomy 18 with no evidence of mosaicism. Analysis of follow-up tissue confirmed trisomy in a foetal skin sample and mosaicism for trisomy 18 in four placental sites tested. CONCLUSION: We report here an apparently normal CVS QF-PCR result that was completely discrepant with the trisomy 18 positive karyotype result on long-term culture. This has important implications regarding our current testing protocol.

A further case of confined placental mosaicism for trisomy 2 associated with adverse pregnancy outcome.

OBJECTIVES: To add to the knowledge base concerning confined placental mosaicism for trisomy 2. METHODS: Cytogenetic study of a late CVS referred for hyperechogenic bowel and raised AFP, and cytogenetic and molecular genetic study of a follow-up amniocentesis. Ultrasound monitoring at regular intervals following the CVS result. RESULTS: All cells examined from direct and cultured CVS showed a 47,XY,+2 karyotype. Amniocentesis showed a mosaic 47,XY,+2[8]/46,XY[81] karyotype. Uniparental disomy (UPD) studies on the amniotic fluid showed normal biparental inheritance. The pregnancy developed oligohydramnios and IUGR and resulted in a 26-week liveborn male infant with a 46,XY karyotype, which died after 3 days because of complications of severe prematurity. Placental villi post delivery showed only the 47,XY,+2 cell line. CONCLUSIONS: This case represents a further example of confined placental mosaicism (CPM) for trisomy 2 associated with oligohydramnios, IUGR and poor pregnancy outcome.

First-trimester prenatal diagnosis of a familial subtelomeric translocation.

A new fluorescent in situ hybridization (FISH) technique utilizes a complete set of telomeric probes to screen for deletions or rearrangements within the subtelomeric regions of all chromosomes on a single slide. Such cryptic chromosome rearrangements would otherwise remain undetected by standard cytogenetic analysis. In this case report, we describe the first-trimester prenatal diagnosis of an unbalanced rearrangement in a family where such a cryptic subtelomeric rearrangement is segregating. Interestingly the fetus was also noted to have an increased nuchal translucency at the time first-trimester chorionic villus sampling was performed and a FISH diagnosis made. The result was subsequently confirmed on fetal material obtained after elective termination of the pregnancy. We believe this to be the first report in the literature (as by Medline, December 1999) of a first-trimester prenatal diagnosis using such subtelomeric probes where confirmation by conventional cytogenetic analysis was not possible.

Prenatal diagnosis of mosaicism for partial trisomy 8: a case report including fetal pathology.

A case of prenatally diagnosed partial trisomy 8 is described. The 'syndrome' is associated with skeletal and cardiac anomalies, as well as hepatic calcification. Differing proportions of 47,XY, +der(8) and 46 XY were present in the different fetal tissues sampled. The highest proportion of 47,XY,+der(8) cells was found in the placenta.

Assessment of chromosome 3 copy number in ocular melanoma using fluorescence in situ hybridization.

Recent reports have indicated that monosomy 3 is a marker of poor prognosis in uveal melanoma. Fluorescence in situ hybridization (FISH) was performed on fresh touch preparations from 17 uveal, and 5 conjunctival melanomas, using the chromosome 3 centromeric probe, D3Z1. Of the 17 uveal melanomas, all of which originated in the choroid, two cases revealed a monosomy of chromosome 3. One of the conjunctival melanomas contained a major clone that was trisomic for chromosome 3, and another conjunctival melanoma contained a tetrasomic population. FISH, using the alpha-satellite probe for chromosome 3 on uveal melanoma imprints, allows one to predict which patients are potentially at a higher risk of relapse. Multiplication, rather than deletion, of copies of chromosome 3 in conjunctival melanomas may be a nonspecific aberration, perhaps indicative of polyploidy, a characteristic of tumor progression.

Prospective prenatal diagnosis of Prader-Willi syndrome due to maternal disomy for chromosome 15 following trisomic zygote rescue.

We present a prenatal predictive diagnosis of Prader-Willi syndrome arising as a result of maternal heterodisomy for chromosome 15. The diagnosis arose following chorionic villus sampling which showed a mosaic trisomy 15 karyotype with a chromosomally normal follow-up amninocentesis. Molecular studies on DNA extracted from cultured amniocytes showed no evidence of a paternal allele at two widely separated loci and this was taken as evidence of maternal disomy predictive of Prader-Willi syndrome in the fetus.

Structural chromosome anomalies in congenital diaphragmatic hernia.

In order to determine the outcome and associated chromosomal and structural anomalies in fetuses diagnosed in utero as having a congenital diaphragmatic hernia, we reviewed 48 consecutive cases referred to our regional Fetal Diagnostic Unit between 1988 and 1995. All babies were delivered in units with appropriate neonatal resuscitation facilities. Thirteen babies [34 per cent of those tested, confidence interval (CI) 19-49 per cent] had karyotypic abnormalities. Three had trisomies but the other nine had more complex karyotypic abnormalities including translocations, deletions, and marker chromosomes. Twenty-one fetuses (44 per cent, CI 30-58 per cent) had additional ultrasound abnormalities which affected the heart in ten cases (21 per cent). Overall, 13 babies survived (27 per cent, CI 14-40 per cent). In babies with normal chromosomes and no additional structural abnormalities the survival rate was 50 per cent (CI 25-75 per cent). Poor outcome was not predicted by early gestation at diagnosis, the hernial contents, or the presence of polyhydramnios. We conclude that parents should be counselled about prognosis with information derived from series of prenatally diagnosed diaphragmatic hernias. The investigations offered should include a detailed ultrasound examination, particularly of the heart, and karyotyping by fetal blood sampling.

Confined placental mosaicism, IUGR, and adverse pregnancy outcome: a controlled retrospective U.K. collaborative survey.

In a retrospective collaborative study involving 21 U.K. laboratories and 11,775 CVS prenatal diagnostic procedures, a total of 73 cases of confined placental mosaicism (CPM) were identified among the 8004 first-trimester referrals because of advanced maternal age, a previous child with a numerical chromosome abnormality, or a family history of the same. Data were collected on subsequent cytogenetic follow-up and pregnancy outcome for each case and a referral matched control. Comparison with the control population failed to demonstrate a marked increase in adverse pregnancy outcome in the CPM group, but a significant increase in both low and high birth weight infants was recorded. In a parallel study, 7 out of 108 cases, referred for prenatal diagnosis because of ultrasound detection of isolated intrauterine growth retardation (IUGR) in the second or third trimester, were shown to have a chromosome abnormality restricted to the extraembryonic tissues. These included cases of CPM involving trisomy 9 and del(13)(q13), neither of which has previously been reported in association with IUGR.

Cytogenetic abnormalities of small round cell tumours.

Between 1987 and 1991, cytogenetic studies were carried out on small round cell tumours of 68 patients from the Northern Health Region of England. Clonal chromosome abnormalities were found in 30, comprising 15 neuroblastomas, 7 Ewing's tumours, 7 rhabdomyosarcomas, and 1 granular cell tumour. Characteristic rearrangements were found in five cases of Ewing's tumour [all with translocation t(11;22) (q24;q12)] and in four cases of rhabdomyosarcoma [all with evidence of translocation t(2;13) (q35-37;q14)]. In one case of Ewing's tumour and three of rhabdomyosarcoma, the cytogenetic findings were important in diagnosis. Within the neuroblastomas, examples were found of hyperdiploidy, 1p rearrangements, double minute chromosomes, and homogeneously staining regions, but too few cases were available for prognostic associations to be assessed. Our findings confirm the diagnostic importance of chromosome abnormalities in small round cell tumours and indicate that cytogenetic analysis should be an intrinsic part of the initial investigations of all patients with such tumours.

Epidermal mosaicism and Blaschko's lines.

To test the hypothesis that epidermal rather than dermal mosaicism determines Blaschko's lines in hypomelanosis of Ito (HI), we studied the distribution of chromosomal mosaicism in four patients. In two, mosaicism had not been detected in lymphocytes or dermal fibroblasts, but was clearly shown in epidermal keratinocytes; furthermore, the abnormal cell line was confirmed to the hypopigmented epidermis and the normal epidermis contained only normal cells. Negative findings in the other two patients might be because of mosaicism which was undetected either because it was submicroscopic or because it was present in melanocytes, which have not yet been studied. These preliminary results support the ideas that (1) Blaschko's lines represent single clones of epidermal cells; (2) in patients with HI and severe neurological involvement mosaicism, if detectable, is best shown in keratinocytes; and (3) the cytogenetic defect in epidermal cells may be directly responsible for the failure of pigmentation in HI.

Cytogenetic abnormalities in a disseminated medulloblastoma.

A 3-year-old girl developed central nervous system, bone and bone marrow metastases, and hypercalcaemia shortly after presentation with medulloblastoma. Cytogenetic studies of the involved bone marrow showed multiple abnormalities including iso(17q). This chromosome rearrangement has been reported in other cases of recurrent or disseminated medulloblastoma. More studies are required relating the karyotypes of medulloblastomas to long-term outcome to determine if the presence of iso(17q) is a prognostic factor in this malignancy.

Meiotic and sperm chromosome analysis in a male carrier of an inverted insertion (3;10)(q13.2;p14p13).

A phenotypically normal male who fathered a son with the karyotype 46,XY,del(10)(p13) was found to be a balanced carrier of an inverted insertion (3;10) (q13.2;p14p13). Karyotyping five later pregnancies showed four to be unbalanced with respect to the insertion, one of which was also trisomic for chromosome 18. The latest pregnancy was balanced with respect to insertion but had the additional complexity of 47,XXY. In the light of six out of six chromosomally abnormal pregnancies, two of which potentially exhibit an interchromosomal effect, it was decided to investigate the gametic output of the father. Testicular biopsy and semen samples were obtained permitting both meiotic and sperm chromosome analysis. Information was thus obtained at three levels of gamete production, that is, prophase I pairing, chiasma frequency distribution at metaphase I, and sperm karyotypes. Electron microscope studies of synaptonemal complexes showed the rearranged chromosomes to pair fully in meiotic prophase I with no indication of the presence of an insertion. This non-homologous pairing of the inserted region was accompanied by an abnormal frequency distribution of pachytene substages. There was also a reduction in chiasma frequency throughout the genome. However, this did not lead to detectable autosomal univalence or abnormally high X/Y univalence. Thus, the trisomy 18 and XXY pregnancies are unlikely to reflect increased non-disjunctional rates either before or during the first meiotic division. Sperm karyotyping showed that the proportion of chromosomally balanced:unbalanced gametes did not differ from the theoretically expected 1:1. There was no evidence of any increase of unrelated abnormalities in the sperm, further indicating that the overall rate of meiotic non-disjunction was not increased above normal.

Cytogenetic analysis of a congenital fibrosarcoma.

Congenital (infantile) fibrosarcoma is a rare soft tissue sarcoma occurring in children aged less than 5 years. We performed cytogenetic analysis on such a tumor, which had an abnormal karyotype: 48,XY, +11, +20. Three other reports of karyotypes in congenital fibrosarcoma describe similar cytogenetic changes, and a specific pattern of trisomies that may prove diagnostic for this tumor is beginning to emerge.

Cytogenetic analysis of a granulocytic sarcoma in a patient without systemic leukaemia.

Granulocytic sarcoma is a rare complication of leukaemia. Occasionally it presents before the development of systemic leukaemia when diagnosis may be difficult. A case of granulocytic sarcoma occurring in a patient with no overt evidence of leukaemia, but in whom cytogenetic analysis of the bone marrow showed a clonal t(12;13) translocation, is reported. Cytogenetic analysis of tissues in this disease may indicate evidence of systemic disease before overt morphological changes.

De novo Ph negative T-cell lymphoblastic leukaemia associated with bcr gene rearrangement.

One case of de novo Ph-negative T-cell acute lymphoblastic leukaemia has been found to have a classical breakpoint cluster region (bcr) rearrangement of the type seen in chronic granulocytic leukaemia. There were no haematological features to suggest a previous chronic phase. This case represents the first report of this rearrangement in Ph negative acute T-lymphoblastic leukaemia at presentation. The implications for various therapeutic options in such patients are discussed.

Chromosome 22 abnormalities in Ewing's sarcoma.

A child with disseminated Ewing's sarcoma underwent cytogenetic investigations which showed different structural rearrangements of chromosome 22 at diagnosis (?ring22), and at relapse [t(10;22)], but the classic translocation t(11;22) was not detectable. This case provides further evidence of the importance of chromosome 22 in this disease, while raising some questions about the central importance of the translocation between chromosomes 11 and 22.

Prader Willi syndrome with hypothyroidism.

A case of Prader Willi Syndrome who suffered from hypothyroidism is described. This patient on cytogenetic examination was found to have Mosaic 46,XX/46,XX,del(15)(q11.1q11.2) karyotype.

Chromosome studies of males in an institution for the mentally handicapped.

Karyotypes were examined in 512 (91.9%) of 557 male patients in an institution for the mentally handicapped. A total of 110 (21.5%) had an abnormal karyotype: 65 (12.7%) with Down's syndrome, 30 (5.9%) with the fragile X syndrome, 13 (2.5%) with autosomal anomalies other than Down's syndrome (12 unbalanced, one balanced), and two (0.4%) with sex chromosome anomalies.