Population screening for aneuploidy using maternal age and ultrasound.

The coexistence of an epidemiological register and a multidisciplinary centre for prenatal diagnosis promoted us to report data collected during six years (1990-1995) in Isère county on prenatally detected chromosomal aberrations. During the whole study period prenatal diagnosis strategy towards chromosome aberrations was based solely on maternal age and ultrasound examination. Results showed a respective contribution of one-third/two-thirds for the two detection modes (maternal age/ultrasound signs). From 1990 to 1995 a significant increase in the proportion of prenatally detected autosomal aneuploidy was observed, from 52 per cent to 75 per cent (P < 0.001). This significant variation was mainly due to an increase in the proportion of prenatally detected trisomy 21 cases, and to an increase in the proportion of aberrations which were detected through first trimester ultrasound examination. The highest positive predictive values were observed for polymalformation, cardiac anomalies and cystic hygroma ultrasound signs (51 per cent, 21 per cent and 26 per cent, respectively). Our results for trisomy 21 are close to those obtained in other studies, even when prenatal strategies are different. Their interest lies in the fact that they can be considered as a reference level of prenatal diagnosis efficiency due to a strategy based on maternal age and ultrasound signs, a level which has to be taken into account when evaluating the benefits of additional serum screening policies in other studies.

Application of fluorescence in situ hybridization to the identification of different marker chromosomes.

Chromosome studies performed on lymphocyte culture of a baby with specific dysmorphism and congenital anomalies suggestive of trisomy 21 revealed a mosaicism: 46,XY,rea(21q21q) [25]/47,XY,rea(21q21q),+mar1[25]. The karyotype of the mother is normal, but the father's karyotype presents an supernumerary chromosome greater and different from the marker of his son: 47,XY,+mar2 (100%). The identification of the two marker chromosomes by standard cytogenetic techniques followed by molecular techniques is essential for the identification of the origin of these two chromosomes. The unusual presence of two different markers one in the father and one in the son, as well as the clinical features of the child, are presented. The possible role of the paternal marker, in the de novo chromosomal rearrangement in his child will be discussed.

[Role of karyotype in studying male infertility]. / Place du caryotype dans l'exploration de l'infertilité masculine.

The karyotype of 443 infertile males has been studied (infertility of unknown etiology). The sample has been divided in 3 groups according to the data of their spermogram: Gr 1--101 males with a normal spermogramm (selected through the sterility of their couple). Gr 2--185 infertile males with oligospermy (less than 20 millions spermatozoal/ml). Gr 3--157 infertile males with azoospermia. This study shows: --No significant difference in chromosomal aberration rate between group 1 and general male population. --A rate of 5% chromosomal aberration in group 2 (versus 0.7% in normal male population p less than or equal to 10(-8], nearly exclusively balanced translocations. --A rate of 21% chromosomal aberration in group 3, nearly exclusively 47, XXY or 46, XX (p less than or equal to -9). The karyotype is unlikely to bring any information in infertile males with normal spermogram; on the contrary it is of valuable interest in infertile males with abnormal sperm.

[Choriocentesis: comparison of the effectiveness of a new choriocentesis needle and a transcervical biopsy forceps]. / Choriocentèse: comparaison des performances d'une nouvelle aiguille à choriocentèse et de la pince à biopsie transcervicale.

71 samples taken by the transabdominal route were compared with 71 samples taken by forceps through the cervix. A fine (1 mm) transabdominal choriocentesis needle with a thin wall (0.1 mm), a short bevel, and a lateral hole was made to bring together simplicity, effectiveness and safety; success was obtained in 95% of the cases (39/41) of our last 41 samples on the first attempt. For comparison with the forceps, the success rate on the first attempt was only 66% (26/41), but it rose to 97.5% if the patient could take 3 attempts at most. The forceps made it possible to collect a mean quantity large enough (19.9 mg) but it was quite variable (16.7 mg being the range) of complete villi, whereas the choriocentesis needle only gathered a smaller volume (12.7 mg) but more reliable (the range being 3.7 mg). The villi were fragmented, however. To work out the study of the DNA and the karyotype, there is a choice between the forceps and the needle. This choice depends principally on the damage the two techniques can do. This has not been worked out yet in our study except indirectly.

[Prenatal diagnosis of 4 cases of spina bifida in mothers treated with valproate]. / Dépistage prénatal de 4 cas de spina bifida chez de mères traitées par le valproate.

The potential risk of spina bifida (SB) after fetal exposure to Valproate led the authors to apply the following protocol: in case of first trimester exposure to Valproate, prenatal diagnosis is offered and consists of both amniotic fluid examination and fetal ultrasound to detect open spina bifida. In the period 1983 to June, 1986, this program allowed early detection of three cases of SB and pregnancy termination. Another case escaped the programme: neural tube defect was detected lately and the child had to be operated upon. These four cases of SB underline the necessity of prenatal diagnosis with combined use and confrontation of ultrasound examination and biochemical amniotic fluid tests.

[Unusual increase in amniotic fluid alpha fetoprotein and trisomy 13]. / Elévation inhabituelle de l'alpha-foetoprotéine du liquide amniotique et trisomie 13.

From 10 observations of trisomy 13, 3 presented an elevated amniotic fluid alpha-fetoprotein level considered as unusual in 2 cases, superior to cut-off level in the other case. Macroscopic examination of the three fetus could not reveal a cause of AFP elevation, neural tube defect or abdominal wall defect. The authors discuss the role of an undetected abnormality such as minor scalp defect with very thin membrane and for one case false-negative result of Kleihauer test.

[Reciprocal translocation at the origin of a Robertsonian translocation 15;22 by the loss of a metacentric chromosome. Genetic counseling]. / Translocation réciproque à l'origine d'une translocation Robertsonienne 15;22 par perte d'un chromosome métacentrique. Conseil génétique.

One of the children of a t(15;22) (q111;p11) woman has lost the minute metacentric der(15) without any clinical consequence, indicating the inocuity of the 15pter----q111 and 22pter----p11 monosomies. The segregation mechanism of this monosomy and, from this family, the relation between reciprocal translocations and Robertsonian translocations are discussed. Another subject with r(22) in the same family questions on an hypothetic common origin.

[Cytogenetic analysis of the Bloom syndrome. A study of the exchange-break relationship]. / Analyse cytogénétique du syndrome de Bloom. Etude de la relation échange-cassure.

Cytogenetic study of a case of Bloom's syndrome (number 46 of the international registry) confirms the excess of exchanges in all cellular types with the exception of a minority of lymphocytes and of two lymphoblastoid cell lines. These exchanges are produced in an X or U fashion between sister chromatids or between homologous chromatids and produce both simple and complex figures for which symmetry is the common feature. Some of these structures are rearranged secondarily, producing centric or acentric fragments and marker chromosomes. Triradial configurations are considered to be the result of exchanges rather than of partial endoreduplication. Chromatid and chromosome breaks are interpreted to result from incomplete exchanges. It is suggested that the general propensity for exchanges is the primary event responsible directly or indirectly for the cytogenetic observations rather than a defect in one of the DNA-repair mechanisms. No increase in mitomycin C sensitivity appears in vitro. The excess of SCEs is partially correlated by contact in vitro with normal cells and to a lesser degree by the culture medium in which the cells were grown.

[Cytogenetic aspects of diffuse scleroderma. Structural anomalies and sister chromatid exchanges]. / Aspects cytogénétiques de la sclérodermie généralisée. Anomalies structurales et échanges de chromatides-soeurs.

Structural chromosome anomalies (1 477 cells examined) and sister chromatid exchanges after two replication cycles with BrdU (771 cells studied) were evaluated in 12 patients with diffuse scleroderma and having received no recent or important irradiation. The increase of structural anomalies, chromatidic as well as chromosomal, is always low, inconstant and cannot be considered as having a diagnostic value. Increase of sister chromatid exchanges could be a more sensitive method of investigation. In particular, it is not influenced by low doses of diagnostic X-rays.

[Mechanism of duplication formation relating to a case of 10q22 to q25 duplication]. / Mécanismes de formation des duplications a propos d'une observation de duplication 10q22àq25.

A duplication 10q22q25 was studied in the fetus of a mother carrier of a t(14q21q). On this occasion, duplications reported in the literature are reviewed. Chromosomal rearrangements involving two breaks always result in tandem duplications, while three break- rearrangements result in tandem or mirror adjacent duplications, or in non adjacent direct or inverted duplications, or in direct or inverted autointerstitial duplications.

[Cytogenetic aspects of diffuse scleroderma : structural anomalies and sister chromatid exchanges (author's transl)]. / De la sclérodermie généralisée aspects cytogénétiques: anomalies structurales et échanges de chromatides-soeurs.

Structural chromosome anomalies (1 477 cells examined) and sister chromatid exchanges after two replication cycles with BrdU (771 cells studied) were evaluated in 12 patients with diffuse scleroderma and having received no recent or important irradiation. The increase of structural anomalies, chromatidic as well as chromosomal, is always low, inconstant and cannot be considered as having a diagnostic value. Increase of sister chromatid exchanges could be a more sensitive method of investigation. In particular, it is not influenced by low doses of diagnostic X-rays.

[Ring-20 chromosome: a new syndrome]. / Chromosome 20 en anneau: un nouveau syndrome.

A comparative study of five observations of a r (20) syndrome characterized by facial dysmorphism, the absence of severe malformations, and rather late onset of encephalopathy and seizures.

[Ring chromosome 14 in monozygotic twins]. / Chromosome 14 en anneau chez des jumelles monozygotes.

An r(14) is observed in monozygotic twins, with psychomotor retardation and no obvious somatic malformation.

Partial trisomy for the long arms of chromosome no. 5 due to insertion and further 'aneusomie de recombinaison'.

Five members of a family with a balanced insertion (1;5)(q32;q11q22) are presented. The daughter of one of them shows multiple malformations and a partial trisomy for the long arms of chromosome No. 5 (5q11 to 5q22 segment) resulting from a 'aneusomie de recombinaison' in her mother. The propositus' karyotype is 46,XX,rec(1;5)ins (1;5)(q32;q11q22). This case is the first reported example of an insertion between two chromosomes followed by 'aneusomie de recombinaison'. It also is the first reported case of trisomy invovling the long arms of chromosome No. 5.