Clinical relevance of diagnosing structural chromosome abnormalities in couples with repeated miscarriage

BACKGROUND

The annual number of parental karyotypes in cases of repeated miscarriage is increasing gradually in The Netherlands. The efficiency of offering parental karyotyping in couples with repeated miscarriage has not been evaluated before, especially not for the group with miscarriages at advanced maternal age.

METHODS

A historical cohort study and nested case-control study were conducted, including couples with at least two miscarriages. Data were retrieved from medical records and telephone interviews. The obstetric follow-up was recorded for > or =2 years after the parental chromosome analysis. Data were analysed to compare ratios of carrier/non-carrier couples in whom maternal age was > or =36 or <36 years at the second, third or fourth and more miscarriage. A projected prevalence of carrier status of a structural chromosome abnormality was calculated by extrapolating the number of included patients to the original level of the total screening population.

RESULTS

Forty-one couples with carrier status of a structural chromosome abnormality and 74 couples without carrier status were included. No unbalanced offspring arose after the detection of a structural chromosome abnormality. The risk of being a carrier was not significantly lower (as might be expected) when women were > or =36 years. Ascertainment after two, three, or four and more miscarriages did not change these findings.

CONCLUSIONS

Karyotyping of 1324 couples ascertained for repeated miscarriage did not yield an unbalanced fetal chromosome pattern after the ascertainment of parental carrier status. In women with advanced maternal age, the frequency of carrier status was not lower than in younger women.

Genetic knowledge and counselling skills of Dutch cardiologists: sufficient for the genomics era?

AIMS

Genetic scientific knowledge is growing rapidly but how this affects clinical practice is unclear. We investigated the levels of knowledge, practical skills and clinical genetic practices of Dutch cardiologists.

METHODS AND RESULTS

A survey was designed to assess cardiologists' experience with genetic aspects of hypertrophic cardiomyopathy, self-reported genetic knowledge, and genetic skills in general and aimed at this disease. In addition, cardiologists' opinions on five possible measures for improvement were obtained.

STUDY POPULATION

all Dutch cardiologists (n=643). Median number of patients suffering from hypertrophic cardiomyopathy per cardiologist is five. Forty-one percent of respondents do not give information about genetics to all their patients. Cardiologists rarely initiate DNA tests for hypertrophic cardiomyopathy. Only 38% refer patients to clinical geneticists. Self-reported knowledge levels are low (average score 3.3-5.1, 0-10 scale). Cardiologists with an established working relationship with a clinical geneticist report significantly higher levels of knowledge. Clinical guidelines, education and improved collaboration with clinical geneticists are preferred.

CONCLUSION

Dutch cardiologists' genetic knowledge and clinical genetic practice levels are insufficient. As a result, clinical genetic care for patients with hypertrophic cardiomyopathy is poor. Improvements proposed include advancement of knowledge (education, professional guidelines) and structural measures (working relationships, multidisciplinary outpatient clinics). Collaboration of cardiologists and clinical geneticists is urgently needed to optimise cardiogenetic patient care.

[Prenatal diagnosis for hereditary predisposition to mammary and ovarian carcinoma--defining a position]

Prenatal testing for a BRCA mutation, the hereditary trait for mammary and ovarian carcinoma, with the intention of selective termination of pregnancy in case of a female carrier is a controversial ethical issue. Based on a review of the (limited) medical literature as well as of Dutch policy statements relating to this subject, the following conclusions and recommendations are proposed: (a) the decision to opt for prenatal BRCA testing and selective termination of pregnancy in case of a BRCA mutation in the foetus cannot immediately be judged unacceptable from an ethical point of view; (b) prenatal BRCA testing is morally defensible only in case of a female foetus and if the parents at least have the intention to terminate the pregnancy if the foetus is a carrier, although the final decision is in any case up to the parents only; (c) prental testing for a BRCA mutation should only be done after extensive counselling of the parents, during which not only the medical genetic aspects but also the ethical aspects of prenatal BRCA testing are discussed.

FISH analysis of fetal nucleated red blood cells from CVS washings in cases of aneuploidy

OBJECTIVE

In chorionic villus sampling (CVS) the chromosome analysis is inconclusive in 1-2% of the samples. In many cases follow-up amniocentesis is performed. Fetal nucleated red blood cells (FNRBCs) are present in washings of chorionic villus samples. We wanted to establish whether analysis of these true fetal cells, using fluorescence in situ hybridization (FISH), could support the CVS karyotype.

METHODS

We analysed washings of first trimester chorionic villi from non-mosaic 45,X (n=6) and full trisomy 18 cases (n=7). FNRBCs were identified by immunostaining and FISH was performed with chromosome-specific probes for X, Y and 18.

RESULTS

In all 13 samples FNRBCs were present (between 4 and 30 cells per sample). Five cases of monosomy X showed one X signal in 89-100% of the nuclei; in the other case 50% of the nuclei displayed one signal. In the trisomy 18 cases three spots were seen in 60-100% of the cells.

CONCLUSION

The CVS aneuploidy was confirmed in FNRBCs in all samples, so FISH on FNRBCs can be used in cases of non-mosaic numerical chromosomal abnormalities. This test can confirm a CVS diagnosis of monosomy X or trisomy 18 and thus minimize the risk for false-positive diagnoses. An additional invasive test may be prevented.

[Prenatal genetic counseling in pregnancy: the importance of (early) timely referral ]

Three women aged 34, 23 and 39 years, who were respectively, 14, 12 and 8 weeks pregnant, requested genetic counselling due to grave genetic diseases in their families. The first woman chiefly wanted to be prepared; an investigation revealed no abnormalities and a healthy child was born. The second needed time to assimilate the information provided and terminated the pregnancy. For the third woman genetic screening was not possible in the short term and furthermore acceptation of the pregnancy was the biggest problem; she gave birth to a healthy child. In the Netherlands, about 800 to 1600 women every year request prenatal genetic counselling when they are already pregnant. The disadvantages of this late timing are the disquiet and uneasiness, the lost options and the time pressure under which difficult decisions have to be taken. Causes of this are a lack of genetic knowledge and psychosocial aspects. Ideally, genetic counselling that deals with reproductive issues should take place prior to conception.

[Use of genetics in the Dutch health care system; a memorandum from the Dutch Minister of Health, Welfare and Sports to the Dutch Parliament]

In the memorandum entitled 'The application of genetics in health care', which was sent to the Dutch Parliament in December 2000, the Minister of Health, Welfare and Sport responded to four proposals she had received from the Health Council of the Netherlands during the previous three years. These proposals included reports on in vitro fertilisation, DNA diagnostics, clinical genetic testing and genetic counselling, and pharmacogenetics. Legal aspects dominate the section on the consumer's/patient's position: detailed legal guidelines are provided for difficult family-related issues in genetic counselling. For genetic counselling and clinical genetic testing, permission from the Minister of Health is still required. Criteria have been provided for the public funding of these activities in the shorter term. Clinical geneticists have been asked to develop guidelines for a number of clinical situations, which include predictive genetic testing and genetic testing in children. Moreover both medical and laboratory professionals have already initiated a number of self-regulatory measures. The Minister has adopted most of the proposals received, which means that for the foreseeable future, there is a clearly regulated framework for the responsible use of genetics within the Dutch healthcare system.

A placental diploid cell line is not essential for ongoing trisomy 13 or 18 pregnancies

Viable trisomy 13 or 18 pregnancies may be supported by the presence of a diploid cell line, confined to the outer layer of the placenta (cytotrophoblast). To establish the presence of diploid cells we investigated five random biopsies from placentas of trisomy 13 (n = 8) and trisomy 18 cases (n = 6) of newborn infants and terminated pregnancies by means of fluorescence in situ hybridisation on interphase nuclei (n = 100). In 12 of these 14 placentas (including all five liveborns) 80% or more of the analysed nuclei showed three spots, suggestive of the presence of a full trisomy. In the other two placentas (both cases of trisomy 18) mosaicism was detected at most investigated sites. Thus, in contrast with earlier studies, these results show that a significant diploid cell line present in the placenta, confined to the trophoblast, is not a pre-requisite for intrauterine survival in the investigated cases.

Absence of deleted in azoospermia (DAZ) genes in spermatozoa of infertile men with somatic DAZ deletions

OBJECTIVE

To determine the presence or absence of the deleted in azoospermia (DAZ) gene clusters in the Y-bearing spermatozoa in semen of severely oligozoospermic men or in testicular biopsy samples of azoospermic men with somatic DAZ deletions.

DESIGN

Prospective study.

SETTING

Academic hospital.

PATIENT(S)

Nineteen patients attending our clinics for therapeutic intracytoplasmic injection of sperm.

INTERVENTION(S)

Peripheral blood lymphocytes were used to obtain somatic DNA for analysis using the polymerase chain reaction. Analysis of chromosomes X and Y and the detection of the DAZ gene clusters were carried out with the fluorescence in situ hybridization technique in spermatozoa remaining after intracytoplasmic sperm injection.

MAIN OUTCOME MEASURE(S)

Presence or absence of the DAZ gene clusters in matched somatic DNA and Y-bearing spermatozoa.

RESULT(S)

Seven patients appeared to have a somatic DAZ deletion. Three-color fluorescence in situ hybridization showed that all Y-bearing spermatozoa examined from these men carried the same deletion.

CONCLUSION(S)

The DAZ deletions present in the seven men would all have been transmitted if they had fathered sons through artificial fertilization techniques using the sperm cells examined in this study.

[The heartache of muscular dystrophy]

Duchenne and Becker muscular dystrophy are caused by a mutation in the dystrophin gene, located on the short arm of the X chromosome. Three so called dystrophinopathy patients, a women aged 54 and two men aged 23 and 21 years, suffered from a severe dilated cardiomyopathy. Such a cardiomyopathy can develop in both carriers and patients. In addition, it is often more important for prognosis than muscle weakness. For these two reasons it is important to screen both groups for (early) cardiological abnormalities. If these are present, regular follow-up is necessary to start timely therapy. When cardiological investigations yield normal results, it is advised to screen carriers with a five-year interval. Dystrophinopathy patients should be checked every year, because the cardiomyopathy sometimes develops and deteriorates over a short period of time. Patients with dilated cardiomyopathy and with a positive family history for dilated cardiomyopathy, muscle weakness or high serum creatine kinase activity should be screened for a mutation in the dystrophin gene.

Genetic aspects of miscarriage

Fetal chromosome abnormalities account for about 50% of first-trimester pregnancy losses. Most of these abnormalities are numerical abnormalities (86%) and a low percentage is caused by structural abnormalities (6%) or other genetic mechanisms, including chromosome mosaicism (8%). The recurrence risk of numerical abnormalities is low, so karyotyping of fetal material in case of a miscarriage does not seem worthwhile in daily practice. Half of the structural abnormalities may be inherited from a parent carrying a balanced chromosome translocation or inversion. Parental carriership is found in 4-6% of the couples with recurrent miscarriage. In case of parental carriership of a balanced structural chromosome abnormality, a next pregnancy may result in a child with an unbalanced structural chromosome abnormality. This child can have multiple congenital malformations and/or a mental handicap. Prenatal diagnosis is therefore recommended. Conventional laboratory techniques, such as tissue culturing and karyotyping, or (semi-)direct chromosome technique of chorionic villi, and the recently developed laboratory techniques such as fluorescence in situ hybridization (FISH) and comparative genomic hybridization (CGH), are described successively. Until now, not enough evidence has been available about the role of other genetic mechanisms, such as single-gene abnormalities, uniparental disomy, genomic imprinting, multifactorial disorders and skewed X chromosome, in the occurrence of miscarriages.

[Decoding of the human genome: a milestone, but not the end of the road]

The base sequence of the entire human DNA will be known within only a few years. So far, 16,000 of an expected total of 100,000 genes have been identified. Nowadays there are different stages of molecular unraveling: from fully sequenced genes, including mutations responsible for diseases, down to 'predicted' genes for which no corresponding protein is yet known. Moreover, the genes responsible for many monogenetic conditions have not yet been identified. The revolutionary approach of at random cloning and sequencing was shown to be successful in the recently published genome sequence of the fruit fly. The next landmark will be an overview of the characteristics and activity of every protein that this organism can synthesize. However, protein technology has developed less far than DNA-technology and will be subject of the next project.

Co-variables in first trimester maternal serum screening

The objective of this study was to determined the influence of maternal weight, maternal smoking habits, gravidity, parity and fetal gender on the level of maternal serum marker used in first trimester screening for Down syndrome. A total of 2449 singleton unaffected pregnancies from two centres were studied. Maternal serum free beta-human chorionic gonadotrophin (hCG) and alpha-fetoprotein (AFP) concentrations had been measured in all pregnancies, and pregnancy associated plasma protein (PAPP)-A levels had been measured in 924. All results were expressed as multiples of the gestation specific median (MoM) values after regression, using each centre's own medians. Information on maternal weight was available in 2259 pregnancies, on self-reported current cigarette smoking in 1364 (of whom 117 (8.6%) were smokers), on gravidity in 1371, parity in 1303 and fetal gender in 253. All three markers showed a statistically significant negative association with maternal weight (p<0.0005) and in the subsequent analyses MoM values were weight adjusted using standard methods. The median PAPP-A level in smokers was 0.81 MoM, a significant reduction (p<0.005); free beta-hCG was also reduced (median 0.89 MoM) but not significantly (p=0.17), and AFP was unaltered. The median AFP level in primagravidas was highly significantly greater than that in gravid women (p<0.0005). In PAPP-A the reverse effect was seen but it did not reach statistical significance (p=0.15) and there was no effect for free beta-hCG. Results of a similar magnitude and direction were found for parity. The median level of free beta-hCG was higher (p=0.0005), and the median AFP lower in female pregnancies. Maternal weight and, for PAPP-A, maternal smoking are important first trimester screening co-variables. Gravidity, parity and fetal gender also seem to influence one or more first trimester markers.

[Fluorescence in situ hybridization in the study of chromosomal abnormalities]

Classical cytogenetics has a low resolving power and allows analysis of dividing cells only. In fluorescence in situ hybridization (FISH), a DNA fragment is stained with a fluorescent marker, after which this fragment is brought into contact with a patient's DNA. The stained fragment can bind to a corresponding fragment, revealing its presence or absence. Using FISH, every desired DNA sequence (from a whole chromosome to one gene) can be stained. In this way it is also possible to diagnose microdeletion syndromes, such as the Williams syndrome, the DiGeorge syndrome and submicroscopic chromosome anomalies that play a part in mental handicaps. FISH also allows analysis of non-dividing cells. In this way it is possible for instance rapidly to examine uncultured amniotic fluid cells for the commoner trisomies or to find foetal erythrocytes in a pregnant woman's blood. It is also possible to demonstrate tumour-specific breaking points. By application of FISH to microarrays it is possible to study a large number of genes simultaneously for the presence of a particular number of DNA sequences linked to a clinical abnormality.

Enrichment, identification and analysis of fetal cells from maternal blood: evaluation of a prenatal diagnosis system

In this study we evaluated the performance of a system for the enrichment, identification and analysis of fetal cells in maternal peripheral blood. Blood samples were collected from women after chorionic villus sampling and enriched for the presence of nucleated erythrocytes using a three-step procedure, namely: (a) centrifugation to separate nucleated red blood cells (NRBCs) from the majority of red blood cells (RBCs) and white blood cells (WBCs); (b) selective lysis of the remaining maternal RBCs; (c) separating the NRBCs from the remaining WBCs in a three-layer density gradient. Fetal cells were identified by using a monoclonal antibody against the gamma-chain of fetal haemoglobin (anti-HbF) and a nuclear stain (DAPI). Additionally, to further increase the specificity of the identification, and to eliminate some of the undesired staining by maternal leukocytes, a fluorescent antibody (CD45) was added. The sex chromosome complement of the cells was determined by fluorescence in situ hybridization (FISH) with X and Y-specific probes and the results were compared with the karyotypes obtained after analysis of chorionic villi. Using the described method, in all cases where the woman was carrying a male fetus (n=18) at least one XY cell was found, while no male cells were found in women carrying a female fetus. However, in the majority of cases with a male fetus (n=11) female HbF positive cells were found indicating the presence of maternal nucleated erythrocytes. The study demonstrates that the combination of anti-HbF and CD45 is a useful, but not fully specific, marker for fetal NRBCs and that additional markers are needed.

Cardiac involvement in carriers of Duchenne and Becker muscular dystrophy

A cross-sectional study in a cohort of DNA proven carriers of Duchenne (DMD) and Becker (BMD) muscular dystrophy was undertaken with the following objectives: (1) to estimate the frequency of electrocardiographic (ECG) and echocardiographic abnormalities; (2) to establish the proportion of carriers with dilated cardiomyopathy and (3) to assess possible associations between dilated cardiomyopathy and genotype. One hundred and twenty nine DMD and BMD carriers, aged 18-60 years, were traced through the files of the central register kept at the department of Human Genetics in Leiden. Investigations included full medical history, physical examination, ECG and two-dimensional and M-mode echocardiographic examination. Forty-seven percent had ECG changes. Thirty-six percent (DMD 41%, BMD 27%) had at least one abnormality as is usually found in the male patients. Echocardiographic examination was abnormal in 36% (DMD 38%, BMD 34%). Dilated cardiomyopathy was found in seven DMD carriers (8%), and in none of BMD carriers. In addition, 18% had left ventricle dilatation (DMD 19%, BMD 16%). Only 38% had a completely normal investigation of the heart. We found no association between genotype and cardiac manifestations. Our study underlines that cardiac involvement is part of the dystrophinopathies. Carriers should be told about the increased risk of this complication when asking genetic advice. It also implicates that a complete cardiological evaluation should be performed at least once in all carriers. If left ventricle dilatation or dilated cardiomyopathy is present a yearly follow up is needed, in order to start timely therapy.

A patient with a de novo t (6;9) and an interstitial duplication of (9)(q21.2q22.1)

We report on a 4-year-old child with psychomotor retardation, general hypotonia and only mild dysmorphic features. Her chromosome constitution was 46,XX, t (6;9) (q27;q22.1), dup (9) (q21.2q22.1). This de novo interstitial duplication was confirmed using fluorescence in situ hybridisation (FISH) with band-specific probes. This is the second report of a patient with an interstitial duplication of this region of the long arm of chromosome 9. It is concluded that in a child with an abnormal phenotype and a de novo (apparently) balanced translocation, the possibility of a small duplication or deletion should be considered.

Signs and symptoms of Duchenne muscular dystrophy and Becker muscular dystrophy among carriers in The Netherlands: a cohort study

BACKGROUND

Carriers of Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) may show muscle weakness or dilated cardiomyopathy. Studies focusing on skeletal-muscle involvement were done before DNA analysis was possible. We undertook a cross-sectional study in a population of definite carriers to estimate the proportion and to assess the clinical profile of carriers with symptoms. We also assessed a possible correlation between genotype and phenotype.

METHODS

Carriers of DMD and BMD, aged 18-60 years, were traced through the files of the central register kept at the Department of Human Genetics in Leiden, Netherlands. For each carrier who agreed to participate a medical history was taken, and muscle-strength assessment by hand-held dynamometry and manual muscle testing and cardiological assessment were done.

FINDINGS

129 carriers of muscular dystrophy (85 DMD, 44 BMD) participated in the study. In 90 women from 52 (70%) families, 37 different mutations were found. 28 (22%) women had symptoms. 22 (17%) had muscle weakness, varying from mild to moderately severe. Muscle weakness was found in carriers of DMD and BMD, but dilated cardiomyopathy was found only in seven (8%) carriers of DMD, of whom one had concomitant muscle weakness. There was an unexpectedly high proportion of left-ventricle dilation (18%). No genotype-phenotype correlation was found.

INTERPRETATION

Clinical manifestation of muscle weakness, dilated cardiomyopathy, or both can be found in about a fifth of carriers of DMD and BMD. If left-ventricle dilation is taken into account, the proportion of carriers with symptoms is even higher, amounting to 40%.

Early pregnancy screening for fetal aneuploidy with serum markers and nuchal translucency

We determined the aneuploidy detection rate achievable by early pregnancy screening with pregnancy associated plasma protein (PAPP)-A, free beta human chorionic gonadotrophin (hCG) and ultrasound nuchal translucency (NT) measurement. Women having prenatal diagnosis were scanned, and a blood sample was taken and stored. Stored samples were tested and a total of 37 were found to have Down syndrome, 8 to have Edwards syndrome and 255 were controls. Results were expressed in multiples of the gestation-specific median (MOM) value in the controls after regression and, for the serum markers, maternal weight adjustment. In Down syndrome the medians were for PAPP-A 0.63 MOM (95 per cent confidence interval (CI) 0.45-0.87); free beta-hCG 1.88 MOM (1.33-2.66); and NT 2.34 MOM (1.70-3.22). Using these parameters the expected detection rate for a 5 per cent false-positive rate for different marker combinations were: 55.3 per cent for PAPP-A and free beta-hCG; 68.4 per cent for NT alone; and 84.6 per cent for PAPP-A, free beta-hCG and NT. The median values for Edwards syndrome were: 0.17 MOM for PAPP-A; 0.18 MOM for free beta-hCG; and 2.64 MOM for NT. Early pregnancy screening with the combined measurement of maternal serum PAPP-A and free beta-hCG and fetal nuchal translucency could achieve a high Down syndrome detection rate.

[No consensus on the definition, diagnosis and treatment of habitual abortion in the Netherlands]

OBJECTIVE

To review the current policy in diagnosis and treatment of recurrent miscarriage in the Netherlands.

DESIGN

Cross-sectional survey.

METHOD

A printed questionnaire was sent in 1996 to all 125 departments of gynaecology in the Netherlands with questions about definition, investigation and therapy of recurrent miscarriage.

RESULTS

The response rate was 90% (n = 112). Twenty-nine per cent of the respondents defined recurrent miscarriage as having two or more abortions and 71% as three or more abortions. In 42% of the departments a diagnostic protocol for recurrent miscarriage was present. Diagnostic investigations most frequently performed were vaginal ultrasound (79%), parental chromosome analysis (78%), thyroid-stimulating hormone (72%), lupus anticoagulant (69%), blood glucose (65%), hysterosalpingography (56%) and anticardiolipin antibodies (IgG, IgM) (56%). Therapy most frequently applied was prescription of folic acid (53%).

CONCLUSION

The definition of recurrent miscarriage differed. Uncertainty about a rational diagnostic approach was evident from the large number of tests requested by 20-50% of the respondents. Some diagnostic tests like immunological investigation and search for infectious factors were not followed by a therapeutical intervention.

Enlarged nuchal translucency and low serum protein concentrations as possible markers for Zellweger syndrome

We present a case of a fetus in which an enlarged nuchal translucency was detected at 12 weeks' gestation. The karyotype was normal. Subsequent ultrasound examination showed no obvious fetal abnormalities apart from a mild pericardial effusion. Serum screening revealed very low concentrations of estriol and human chorionic gonadotropin. After birth the diagnosis of Zellweger syndrome was made. Nuchal translucency screening, estriol level identification and detailed ultrasound scanning may help to identify fetuses affected by this syndrome.

First-trimester non-invasive prenatal diagnosis of triploidy

We report a case of fetal triploidy in which fetal nucleated red blood cells were isolated from the maternal peripheral circulation at 12 weeks' gestation. FISH analysis with X and Y specific probes revealed three hybridization signals for the X chromosomes in 14 cells. The karyotype as established after CVS was shown to be 69,XXX. Two other non-invasive first-trimester screening methods were also evaluated. The serum markers pregnancy-associated plasma protein A (PAPP-A) and the free beta-chain of chorionic gonadotrophin (free beta-hCG) were both shown to be decreased in the same blood sample. An enlarged nuchal translucency (5 mm > or =95th centile) was seen at 13+2 weeks of gestation.

Low-level mosaicism for both trisomy 15 and monosomy-X in amniotic fluid cells confirmed in fetal tissues

We report here a case of true fetal mosaicism for both trisomy 15 and monosomy-X; the aberrant cell lines were initially detected at amniocentesis as low-level mosaicism (trisomy 15) and multiple-cell pseudo-mosaicism (monosomy-X). In the fetal lymphocytes, only metaphases with a normal chromosome complement were observed. After termination of the pregnancy, various fetal biopsies revealed both trisomy 15 and monosomy-X mosaicism, whereas, at autopsy, no external or internal abnormalities could be detected in the fetus. The karyotype can be described as 45,X[15]/47,XY,+15[3]/46,XY[27]. Our results implicate that an additional amniocentesis could be more helpful than fetal blood sampling in predicting the fetal karyotype after diagnosis of chromosome mosaicism at amniocentesis.