A low rate of trisomy 21 in twin-pregnancies: a cytogenetics retrospective study of 278 cases.

From January 1st 1990 until December 31st 2001, we collected 19686 prenatal diagnosis (on amniocentesis and chorius villus sampling). Five hundred twelve samples (2.6%) concerned 278 twin pregnancies. The most frequent indications were maternal age > or = 35 years (108/278 = 38.8%), medically assisted procreation (34/278 = 12.3%), positive ultrasound (20/278 = 7.2%). Chromosome abnormalities were found in eight twin-pregnancies (2.9%): five with only one fetus affected [47,XX,+ 18; 45,XX,t( 13;14); 47,XYY; 47,XXX; 45,XX, t(13;14)], two with both fetuses showing the same chromosomal abnormality [inv(11)(q21q25); 47,XX,+ 18] and one with only one fetus tested [47,XX,+ 18]. In total, we found eight autosomal abnormalities, four inherited balanced rearrangements (two robertsonian translocations and two paracentric inversions of chromosome 11) and four trisomies 18. We also observed two sex chromosome abnormalities interesting only one of the two fetuses. Surprisingly, we did no detect any Down Syndrome among this population. The frequency of Down Syndrome was significantly (p < 0.05) lower in our population of twin pregnancies (0.0%) as compared to the observed incidence in singleton pregnancies during the same period (163/19162 = 0.9%).

Major decrease in the incidence of trisomy 21 at birth in south Belgium: mass impact of triple test?

In South Belgium (Wallonia), the 'triple test' was introduced in 1990-1991, and is nowadays a widely accepted screening method for assessment of trisomy 21 risk in pregnancy. The 'triple test' is not regulated and can be freely performed by any biomedical lab, making epidemiological data unavailable. By contrast, cytogenetic investigations are limited to a few genetic centres, and accurate statistics can be easily built from their files. During the period 1984-1989, a total of 244 trisomy 21 (1/876 pregnancies) were diagnosed in the Genetic Centres of Liège and Loverval, 42 (17%) of them prenatally. During the period 1993-1998, 294 trisomy 21 (1/704 pregnancies) were observed, 165 (56%) of which prenatally, and more than 90% of affected pregnancies were terminated. Even after correction for late foetal loss of trisomic foetuses, the difference is highly significant, and corresponds to a theoretical shift in the incidence of trisomy 21 at birth from 1/794 to 1/1606. As no remarkable progress occurred in other non-invasive prenatal screening procedures or general health care policies in Belgium, the most reasonable explanation is the use on a large scale of triple test by pregnant women, and the election of termination for most affected pregnancies.

Inv(12)(q15q24): a nonrandom change associated with myelodysplasia?

A patient with refractory anemia and a paracentric inversion of chromosome 12, inv(12)(q15q24), is described. This is the second reported case with this chromosome anomaly, suggesting that this rearrangement is a rare but nonrandom change associated with myelodysplastic syndromes.

Deletion of the 5'-ABL region: a recurrent anomaly detected by fluorescence in situ hybridization in about 10% of Philadelphia-positive chronic myeloid leukaemia patients.

Inclusion of the BCR-ABL ES probe in routine cytogenetics led to the identification of a subgroup of Philadelphia positive (Ph+) chronic myeloid leukaemia patients characterized by a 5'-ABL deletion. This anomaly was observed in 5/51 cases (9.8%). Cytological and clinical data suggest that the 5'-ABL deletion may be associated with dysplastic features of polymorphonuclear cells and metamyelocytes and a short chronic phase duration.

[Genetic counseling and prenatal diagnosis]. / Conseil génétique et diagnostic prénatal.

Fetal medicine is in full expansion thanks to the tremendous progress made in both fetal access techniques and genetic analysis. In this article, we discuss the role of the genetician within a group of prenatal diagnosis and his contribution to the assessment of fetal diagnosis and prognosis. We describe the different approaches (invasive and non invasive) to fetal investigation i.e. ultrasonography, maternal serum screening, preimplantation diagnosis and FISH.

Translocation (2;3)(p21;q26) as the sole anomaly in a case of primary myelofibrosis.

Translocation t(2p;3q) is a rare but recurrent finding in myeloid disorders. We present the first case of primary myelofibrosis with t(2;3)(p21;q26) as the sole chromosomal anomaly. The comparison with the 11 other previously published myeloid-associated t(2p;3q) cases confirms that this nonrandom translocation involves a pluripotent stem cell and is associated with a poor prognosis.

Loss of the Y chromosome in bone marrow cells: results on 1907 consecutive cases of leukaemia and preleukaemia.

Loss of the Y chromosome with a resulting 45, X0 karyotype is observed in normal bone marrow cells of elderly males but also in haematological malignancies. Whether Y loss in neoplastic cells is related to the process seen in normal ageing or is part of the carcinogenic process is unknown. The present study concerns the cytogenetic data from 1907 consecutive leukaemic or preleukaemic male patients with special regard to the presence or absence of the Y chromosome. Sixty-five patients (3.4%) had a 45, X-Y clone in their bone marrow (BM) cells. Loss of Y was rare below the age of 50 but increased in older patients, reaching 25% of the men over 80. Sixteen patients (0.08%) had more than 90% X0 cells in their BM. A correlation between Y loss and leukaemia could be established in seven cases, three of which were acute myeloid leukaemia M2 subtype where -Y is known to be a secondary event. In three other cases, -Y was part of a complex karyotype. Only one patient exhibited a 45, X0 karyotype, with no other rearrangement, that could be positively correlated with the neoplastic process.

Mutation analysis of the MEN1 gene in Belgian patients with multiple endocrine neoplasia type 1 and related diseases.

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant disorder characterized by tumors in parathyroids, enteropancreatic endocrine tissues, anterior pituitary, and other tissues. The gene for MEN1 has recently been cloned and shown to code for a 610-amino acid protein of enigmatic function which probably acts as a tumor suppressor. Several mutations causing the MEN1 phenotype have been recently identified. In order to determine the spectrum of MEN1 gene mutations in a sample of 25 Belgian patients, we have systematically screened the 10 exons and adjacent sequences of the MEN1 gene by means of an automatic sequencing protocol. Twelve different mutations were identified including nonsense, frameshift, splicing, and missense mutations. Two of these mutations (D172Y and 357del4) occurred more than once. A missense mutation was also found in a kindred with familial hyperparathyroidism. We observed no significant correlation between the nature or position of mutation and the clinical status. We have also detected 6 intragenic polymorphisms and DNA sequence variants and have analyzed their frequencies in our population.

[Programs of systematic screening in neonatology. Pharmaco-economic aspects]. / Les programmes de dépistage systématique en néonatologie. Aspects pharmaco-économiques.

Systematic neonatal screening offers many advantages for the patients, its family and the community. The Genetic center of the University Hospital of Liège provides neonatal screening for the following diseases: phenylketonuria, congenital hypothyroidy, cystic fibrosis, alpha-1-antitrypsin, adrenal hyperplasia and biotinidase deficiency. On economical grounds, it is clear that the organisation of neonatal screening costs less to the community than the cost of the disease if diagnosis is made too late as to allow an alleviation, or even a total recovery, of the symptomatology.

Private multiple congenital anomaly syndromes may result from unbalanced subtle translocations: t(2q;4p) explains the Lambotte syndrome.

In 1990, Lambotte syndrome was reported as an apparently autosomal recessive multiple congenital anomaly/mental retardation (MCA/MR) syndrome observed in 4 of 12 sibs from a probably consanguineous mating [Verloes et al., Am J Med Genet 1990; 37:119-123]. Major manifestations included intrauterine growth retardation (IUGR), microcephaly, large soft pinnae, hypertelorism, beaked nose, and extremely severe neurologic impairment, with holoprosencephaly in one instance. After the observation of a further affected child born of one unaffected sister, in situ hybridization analysis and chromosome painting techniques demonstrated a subtle t(2;4)(q37.1; p16.2) translocation in the mother, suggesting a combination of 2q/4p trisomy/monosomy in all of the affected children of the family. Many private sporadic or recurrent MCA/MR syndromes maybe due to similar symmetric translocations, undetectable by conventional banding techniques.

Nosology of lysosomal glycogen storage diseases without in vitro acid maltase deficiency. Delineation of a neonatal form.

We describe a boy with an early lethal hypertrophic vacuolar cardiomyopathy of neonatal onset. Abnormal intra- and extralysosomal glycogen storage disease was demonstrated in heart and skeletal muscles. Glycogen content was twice the normal in muscles and over 3-fold the normal in the heart. In this organ, over 50% of the intracellular space was occupied by glycogen and possibly oligosaccharides, as demonstrated by the quantitative morphometric analysis of electron micrographs. The activity of acid alpha-glucosidase was increased in the heart, skeletal muscles, and liver, but was normal in leukocytes. A review of the 11 previously published pedigrees of lysosomal glycogen storage disease with normal in vitro alpha-glucosidase activity allows the delineation of three clinical entities: juvenile and neonatal pseudo-Pompe diseases and partial Pompe disease. Partial Pompe disease, due to the tissue-specific absence of acid alpha-glucosidase, was observed in a single patient. The most common form is the late-onset pseudo-Pompe disease, which is characterized by severe cardiomyopathy and mild myopathy appearing in the second or third decade, prominent arrhythmia with Wolf-Parkinson-White syndrome, and sometimes mental retardation. Patients reported as suffering from Antopol disease probably belong to this group. Dominant inheritance (autosomal or X linked) is likely in most families. The present report appears to be the first one to describe a rapidly fatal neonatal form of lysosomal glycogenosis without acid maltase deficiency. The mode of inheritance of this form is not known. Differential diagosis includes Pompe disease (similar histology) and cardiac phosphorylase b kinase deficiency (similar clinical course). The delineation of neonatal pseudo-Pompe disease makes enzymatic confirmation mandatory in each case suspected of Pompe disease.

Microcephaly, muscular build, rhizomelia, and cataracts: description of a possible recessive syndrome and some comments on the use of electronic databases in syndromology.

We report on a 7-year-old boy born of consanguineous parents with severe microcephaly (-5 SD) but borderline intelligence, juvenile cataract, muscular build, rhizomelic shortness of limbs predominantly of femora, advanced bone age, and micropenis. This combination of signs appears unique and may represent an undescribed, possibly autosomal recessive MCA syndrome. The use of LDDB and POSSUM in the workup of such "new syndromes" is reviewed. Three search strategies are discussed: single rare sign browsing, best combinatory fit using an array of key words, and combined rare signs scan. Pitfalls in the use of such databases and the some problems raised by inconsistent/ incomplete encoding in those two popular, highly useful syndromology retrieval systems are discussed.

Genetic risk in natural and medically assisted procreation.

Current in vitro fertilization techniques (IVF) including intracytoplasmic sperm injection (ICSI), microepididymal sperm aspiration (MESA) or testicular sperm extraction (TESE) clearly prevent any spontaneous choice of ova or spermatozoa. According to the widely admitted concept of gamete selection, pregnancies following IVF, when compared to natural fertilization, could therefore present a higher risk of genetic anomalies. However, no increased fetal or newborn abnormalities are noticed with IVF, except perhaps for sex chromosome aneuploidies. Data from the literature support the view that the uterus is, indeed, the organ where selection mechanisms occur (when they do so), as suggested by Carr in 1971. This selection concerns mainly autosome imbalances; unbalanced conceptuses are aborted. Sex chromosome aneuploidies, apparently, are less prone to natural abortion, but their higher rate of occurrence, as reported in a few series of studies, does not seem to be associated with the IVF procedures.

Recurrence of neonatal haemochromatosis in half sibs born of unaffected mothers.

We report two families in which neonatal haemochromatosis was observed in half sibs. In the first family, two successive girls were born of different fathers. In the second family, an affected brother and sister were followed by an affected half brother born after donor insemination. These observations, as well as a previous abstract describing two affected half sisters, revive the debate over the inheritance of neonatal haemochromatosis. Incomplete penetrance or gonadal mosaicism for a dominant disorder, a maternal "environmental factor", or mitochondrial defect may be more suitable explanations than autosomal recessive inheritance in this condition. Alternative modes of fertilisation, such as donor insemination or in vitro fertilisation with donor eggs, should be considered with caution.

Microcephaly, macrotia, unusual mimics and mental retardation syndrome: new syndrome or variant of De Lange type 2 syndrome.

We report a boy who shows a severe microcephaly, with mild mental retardation and hypotonia, and a dysmorphic facies: (flat profile, arched eyebrows, mild ptosis, short nose with raised basis, large tip and anteverted nares, long, smooth philtrum, narrow mouth with down turned corners, very large, backward tilted ears, with a prominent lobule, retrognathism and very small and widely spaced, although normally shaped teeth. Vesicoureteral reflux was present. The mother showed similar aspect, large ears, and a grinning smile. This appear to represent an undescribed phenotype which share some resemblance to mild Cornelia de Lange and Kabuki syndromes.

A new form of skeletal dysplasia with amelogenesis imperfecta and platyspondyly.

We report two patients, born of consanguineous parents, affected by a disorder resulting in mild growth retardation. Hallmarks are amelogenesis imperfecta (absence of the enamel cap) associated with brachyolmia-like anomalies: platyspondyly with short pedicles, narrow intervertebral and interpedicular distances, rectangular-shaped vertebrae with posterior scalloping and herniation of the nuclei, and broad femoral necks. Inheritance appears to be autosomal recessive.

Cytogenetic study of bovine oocytes matured in vitro.

Described in the present paper is a cytogenetic study of bovine oocytes matured in vitro. The cumulus-oocyte complexes (COC), punctured from ovaries recovered in a local slaughterhouse, were classified into 3 groups according to follicular diameter 1 to 4mm, 5 to 8mm and 9 to 13 mm. Metaphases available for observation were classified as metaphase I, haploid and diploid metaphase II. High levels of haploid metaphases II (90.6, 86.9 and 94.4 %) among the 3 groups of follicular sizes indicated successful meiotic resumption during in vitro maturation and suggested that cytoplasmic maturation may be responsible for low developmental rate after IVM, IVF and in vitro development (IVD).

Nuclear lesions during rat hepatocarcinogenesis. I. Measuring the sister-chromatid exchanges during initiation, promotion and progression of rat hepatocarcinogenesis induced with diethylnitrosamine.

Cytogenetic endpoints such as sister-chromatid exchanges (SCEs), chromosomal aberrations and micronuclei (MNs) have been widely used as indicators of genetic damage. However, no systematic attempts have been made to correlate the levels of these cytogenetic endpoints with the different steps of carcinogenesis. In the present report, the induction, accumulation and persistence of SCEs and high frequency cells (HFCs) were measured in liver cells during the initiation, promotion and progression steps of rat hepatocarcinogenesis induced by diethylnitrosamine (DEN). The results indicate that lesions leading to SCEs accumulate during initiation only. When DEN administration is longer than the duration of this first step, SCE values stabilize. After stopping the carcinogenic treatment, the SCE levels decrease to control values whether or not promotion and progression occur.

Nuclear lesions during rat hepatocarcinogenesis. II. Measuring the micronuclei during initiation, promotion and progression of rat hepatocarcinogenesis induced with diethylnitrosamine.

We reported in our companion paper the strong correlation between elevated sister-chromatid exchange (SCE) frequencies and the initiation step of rat hepatocarcinogenesis. We have also shown that SCEs return to normal values during the promotion and the progression stages. In the present study, we evaluated the clastogenic activity of diethylnitrosamine (DEN) during initiation, promotion and progression of rat hepatocarcinogenesis. We measured, at various times after DEN administration, the number of micronuclei (MN) produced by the mitotic response to partial hepatectomy. The results established that the DEN treatment induces a great number of preclastogenic lesions. In subcarcinogenic conditions (initiation alone), the number of MN expressed after partial hepatectomy remains high regardless of the time interval between the end of the DEN treatment and the operation. In this condition, the preclastogenic lesions persist for up to 1 year after the DEN administration is discontinued. Conversely, in carcinogenic conditions (initiation + promotion + progression), the number of MN expressed after partial hepatectomy decreases during the promotion and progression stages. These observations indicate that promotion and progression but not initiation are associated with the expression of persistent preclastogenic lesions, resulting in the production of chromosomally abnormal hepatocytes.