Pregnancy outcome following prenatal diagnosis of an isodicentric X chromosome: first case report.

An isodicentric X chromosome, idic (X)(q27) was found in a female fetus during cytogenetic studies performed on amniotic cells due to advanced maternal age. No mosaicism was observed. Although segmental inversion duplications have been described for several other chromosomes, isodicentric chromosomes are reported only for gonosomes. Genetic counselling was based on ultrasound findings, cytogenetic replication studies and published cases of X chromosomes duplications ascertained pre- and postnatally. The pregnancy resulted in the birth of a healthy female infant.

Chronic lymphocytic leukemia associated with myelodysplastic syndrome and/or chronic myeloid leukemia: evidence for independent clonal chromosomal evolution.

We describe the cytogenetic findings of three cases with simultaneous or sequential development of a B-chronic lymphocytic leukemia (B-CLL) and either a myelodysplastic syndrome (MDS) in 2 cases or a chronic myeloid leukemia (CML) in one case. The coexistence of these two hematologic malignancies leads to questions about their cell of origin. Through analysis of the cytogenetic abnormalities, we studied the derivation of both malignancies. The cytogenetic analyses of these three patients were simultaneously studied from both peripheral blood and bone marrow. Furthermore unstimulated short-time (USSTC) and long-time (72-96 hours) stimulated cultures (LTSC) were systematically performed. In all cases, we have demonstrated the independent bi-clonal evolution. This is the first report ever described for patients with CLPD and MDS and/or MPD shown to arise from distinct chromosomal abnormalities.

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.

Fetus with Casamassima-Morton-Nance syndrome and an inherited (6;9) balanced translocation.

We report on a fetus with cranio-facial anomalies, a narrow thorax, imperforate anus with cloacal cyst, and a genitourinary malformation with absent uterus, vagina, and external genitalia. Major thoracic defects were seen on roentgenographic examination, including absent vertebrae and ribs, a supernumerary vertebra, a hemivertebra, and rib fusion. These findings are compatible with Casamassima-Morton-Nance syndrome. The patient was the carrier of a translocation t(6;9)(p12;q12), inherited from the mother. Although the occurrence of this rearrangement may be coincidental, it may also indicate a possible locus for this autosomal recessive thoracic dysplasia.

[An example of detection of heterozygotes and antenatal diagnosis in four families with anhidrotic ectodermal dysplasia]. / Un exemple de diagnostic d'hétérozygotes et de diagnostic anténatal dans quatre familles de dysplasie ectodermique anhidrotique.

Anhidrotic ectodermal dysplasia is an X-linked inherited skin disorder; only affected males exhibit the complete syndrome, whereas females may have a few mild features. The gene involved in this disease is located in the proximal area of the long arm of the X chromosome, in the q13 position. Molecular analysis is very helpful for calculating the risk of transmission in sisters with normal phenotypes and affected individuals (family 1 provides an example), but cannot solve all problems (example of family 4). The best results are obtained when there are two informative markers, each located on either side of and very close to the mutant gene. Molecular analysis can also be applied to chorionic villi sampled at the tenth week of gestation in order to achieve antenatal diagnosis in male fetuses in high risk families. Until recently, antenatal diagnosis could be performed only at the twentieth week of gestation by the demonstration of inadequate development of skin glands in skin biopsy specimens sampled under fetoscopy. Family 2 provides an example of antenatal diagnosis and highlights the risk of error that always exists in molecular analysis studies.

Chromosomal prenatal diagnosis: study of 936 cases of intrauterine abnormalities after ultrasound assessment.

Nine hundred and thirty-six prenatal chromosomal analyses were performed by four cytogenetic centres after ultrasound diagnosis of fetal abnormalities, amniotic fluid disorders, fetal growth retardation, and fetal or placental abnormalities. During the same period, 6515 fetal karyotypes were analysed because of maternal age. Frequencies of chromosomal aberrations in each case were respectively 4.4, 6.7 and 15.8 per cent, compared with 3.18 per cent when the fetal karyotype was performed because of maternal age. High rates of chromosomal aberrations are observed in cases of cervical hygroma, limb abnormalities, omphaloceles, duodenal stenosis, hydrocephalus, and facial abnormalities. In the case of polymalformations, this rate was 29.2 per cent. When malformations were seen together with an amniotic fluid disorder or growth retardation, 21.5 per cent chromosomal aberrations were observed. This frequency was 10.4 per cent when growth retardation was associated with an amniotic fluid disorder. Trisomy 13, 18, 21 and monosomy X accounted for 4/5 of all abnormalities in which we observed a high rate of triploidies (4.9 per cent) and balanced (3.3 per cent) or unbalanced (9.8 per cent) non-Robertsonian structural abnormalities. Sonographic ascertainment of these aberrations and prenatal characteristics of major anomalies are discussed.

Spondyloepiphyseal dysplasia tarda: linkage with genetic markers from the distal short arm of the X chromosome.

A linkage study of six families with spondyloepiphyseal dysplasia tarda (SEDL) has been performed. A linkage to site DXS41 (theta = 0.08; z = 3.07) and DXS92 (theta = 0.05; z = 2.95) has been established. We propose that the SEDL locus lies on the distal part of the short arm of the X chromosome.

Linkage studies in X-linked Alport's syndrome.

Four kindreds segregating for Alport's syndrome (ASLN) compatible with a X-linked inheritance were studied for linkage with polymorphic markers of the human X chromosome. No recombinant was observed between the ASLN locus and the DXS101 and DXS94 loci, the maximum lod scores were z = 3.93 and 3.50 respectively. Linkage data between the ASLN locus and the other genetic markers used in the present study are in keeping with the assignment of the mutation to the proximal Xq arm.

Linkage studies do not confirm the cytogenetic location of incontinentia pigmenti on Xp11.

Linkage studies have been performed in 5 incontinentia pigmenti (IP) families totaling 29 potentially informative meioses. Ten probes of the Xp arm were used, six of them were precisely localized on the X chromosome, using hamster X human somatic cell hybrids containing a broken X chromosome derived from an incontinentia pigmenti patient carrying an X;9 translocation [46,XX,t(X;9)(p11.21;q34)]. The following order for probes is proposed: pter - (DXS7, DXS146, DXS255) - IP1 - (DXS14, DXS90) - DXS106 - qter. The negative lod scores obtained exclude the possibility that in the families studied, the gene for IP is located in Xp11 or in the major part of the Xp arm.