Supernumerary ring chromosome: an etiology for Pallister-Killian syndrome?

Characterization of marker chromosomes before the introduction of array CGH (aCGH) assays was only based on their banding patterns (G, C, and NOR staining) and fluorescent in situ hybridization techniques. The use of aCGH greatly improves the identification of marker chromosomes in some cases. We describe an atypical case of Pallister-Killian syndrome (PKS) detected at prenatal diagnosis with a very unusual cytogenetic presentation: a supernumerary ring chromosome including two copies of 12p. A similar anomaly described in a postnatal patient suggests ring chromosome as a possible cause of PKS. Extra ring chromosomes might be a more common etiology for PKS than previously thought, given the difficulty in their characterization before the advent of aCGH.

Diagnóstico prenatal de una trisomía16q completa. Presentación de un casoy revisión bibliográfica / Prenatal diagnosis of complete trisomy 16q. Report of one case and review of the literature

La trisomía 16 es la aneuploidia más frecuente en los abortosespontáneos de primer trimestre, siendo incompatible conla vida. Sin embargo, de forma infrecuente han sido descritosrecién nacidos con aneuploidias parciales de este cromosoma.Presentamos el segundo caso diagnosticado prenatalmentede trisomía total del brazo largo del cromosoma 16.El feto era portador de una dotación cromosómica desequilibrada46 XY, der(14) t (14;16) (p10;q10) como consecuenciade una translocación materna (AU)

Full trisomy is the most frequent first trimester spontaneousmiscarriages chromosome aneuploidy, being incompatiblewith life. However, partial aneuploidies of this chromosomehave been uncommonly reported in newborns.We present the second prenatal diagnosis of chromosome16 long arm trisomy. The fetus was found to have an abnormalkaryotype of 46 XY, der (14) t (14;16) (p10;q10) inheritedfrom a maternal translocation (AU)

Detección prenatal de un isocromosoma 20 de brazos largos: presentación de un nuevo caso y revisión de la literatura / Prenatal diagnosis of a long arm isochromosome 20: A new case and literature review

Presentamos un nuevo caso de mosaico de isocromosoma20 de brazos largos, i(20q), diagnosticado prenatalmente,con fenotipo normal al nacimiento, y una exhaustiva revisiónde la literatura.La correcta interpretación del hallazgo prenatal de uni(20q), y en general de una trisomía total o parcial en mosaico,es usualmente difícil debido a la variabilidad en la expresiónde las anomalías en mosaico en los diversos tejidosy a la poca información existente (generalmente hay pocoscasos descritos, la información sobre su seguimiento posnatales escasa y en pocos casos se han podido realizar estudiosconfirmatorios).El riesgo de patología fetal asociado al i(20q) aún no hasido establecido de forma fiable y, por tanto, el dilema delsignificado y pronóstico del i(20q) persiste

The significance of rare partial or total autosomaltrisomy mosaicism is usually very difficult because of thefew cases reported in the literature, the limited informationon phenotypic outcome, and the scarcity of confirmationstudies.We present a new case of mosaicism of long armisochromosome 20, i(20q), diagnosed in a pregnancywith a normal outcome. At present, the precise risk of fetal pathology associatedto i(20q) can not confidently be concluded, so significanceand prognosis dilemma of prenatal mosaicismi(20q) persists (AU)

High EPHB2 mutation rate in gastric but not endometrial tumors with microsatellite instability.

The EPH/EFN family of receptor tyrosine kinases regulates cell adhesion and migration and has an important role in controlling cell positioning in the normal intestinal epithelium. Inactivation of EPHB2 has recently been shown to accelerate tumorigenesis in the colon and rectum, and we have previously demonstrated frequent frameshift mutations (41%) in an A9 coding microsatellite repeat in exon 17 of EPHB2 in colorectal tumors with microsatellite instability (MSI). In this study, we extended these analyses to extracolonic MSI cancers, and found frameshift EPHB2 mutations in 39% (25/64) of gastric tumors and 14% (8/56) of endometrial tumors. Regression analysis of these EPHB2 mutation data on the basis of our previously proposed statistical model identified EPHB2 as a selective target of frameshift mutations in MSI gastric cancers but not in MSI endometrial carcinomas. These results suggest a functional role for EPHB2 in gastric tumor progression, and emphasize the differences between the tumorigenic processes in MSI gastrointestinal and endometrial cancer.

Interpretación y expresión clínica de mosaicos cromosómicos / No disponible

No disponible

Evaluación de la PCR cuantitativa fluorescente para el diagnóstico prenatal rápido de anomalías cromosómicas / Tittle

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Intranuclear arrangement of human chromosome 12 is reflected in metaphase chromosomes as non-random bending.

We have found a high correlation of non-random bending of human metaphase chromosome 12 with the intranuclear arrangement deduced by Nogami et al. (Chromosoma 108 (2000) 514), providing further evidence of the relation of non-random bending and the interphase organization of the nucleus.

Rapid prenatal diagnosis of common chromosome aneuploidies by QF-PCR. Assessment on 18,000 consecutive clinical samples.

The quantitative fluorescent PCR (QF-PCR) assay, introduced during the last few years, allows prenatal diagnoses of common chromosome aneuploidies in a few hours after sampling. We report the first assessment of QF-PCR performed on a large cohort of 18,000 consecutive clinical specimens analysed in two different Centres. All samples were analysed by QF-PCR using several selected STR markers together with amelogenin and, occasionally, SRY for fetal sexing. Results were compared with those obtained by conventional cytogenetic analysis. In 17,129 tests, normal fetuses were detected by QF-PCR. No false positives were observed. All 732 cases of trisomy 21, 18, 13, triploidies, double trisomies as well as all but one fetuses with X and Y aneuploidies were correctly diagnosed. Chromosome mosaicism could also be suspected in several samples. In some cases of in vitro culture failures, QF-PCR was the only evidence of fetal X, Y, 21, 18 and 13 chromosome complement. QF-PCR proved to be efficient and reliable in detecting major numerical chromosome disorders. The main advantages of the molecular assay are its very low cost, speed and automation enabling a single operator to perform up to 40 assays per day. QF-PCR relieves anxiety of most parents within 24 h from sampling and accelerates therapeutic interventions in the case of an abnormal result. In countries where large scale conventional cytogenetics is hampered by its high cost and lack of technical expertise, QF-PCR may be used as the only prenatal diagnostic test.

Prenatal diagnosis of an interstitial 12q chromosome deletion.

Rearrangements involving long arm of chromosome 12 are rare events. To our knowledge, we present the first case of an interstitial deletion of the long arm of chromosome 12 in a prenatal diagnosis. A review of the literature is included in our report.

Two cases of tetrasomy 9p syndrome with tissue limited mosaicism.

Tetrasomy of short arm of chromosome 9 constitutes a clinically recognizable chromosomal syndrome. Isochromosome 9p shows a strong propensity to tissue-limited mosaicism. It occurs predominantly in peripheral blood cultures, often at a lower frequency or even absent in skin, amniotic fluid or chorionic villous cell cultures. Tissue-limited nature of mosaicism may render prenatal detection of this condition very difficult. Herein, we report two new cases of mosaic tetrasomy 9p. Conventional cytogenetics (CC) and FISH studies demonstrated a differential expression of the mosaicism in several tissues. We review the literature and discuss the implications of these findings in cytogenetic prenatal diagnosis.

Early amniocentesis with the filtration technique: neonatal outcome in 123 singleton pregnancies.

OBJECTIVE: To evaluate results of a prospective study of pregnancies in which early amniocentesis with the filtration technique was performed at 10-13 weeks' gestation (mean 12.3 weeks' gestation). METHODS: 123 singleton pregnancies in which early amniocentesis with the modified filtration technique was performed at 10-13 weeks' gestation (mean 12.3 weeks' gestation). The amniotic fluid was aspirated into the syringe and reinjected through the filter. RESULTS: All the procedures were performed successfully by a single needle insertion. Neither dry taps nor filtration failures occurred. The mean time of amniocentesis was 4.02 min (95% confidence interval, 3 min and 36 s to 4 min and 18 s). The karyotyping success rate was 99.2%. Temporary amniotic fluid leakage occurred in three women (2.4%). There were 110 (89.4%) live births. Two cases of stillbirth occurred at week 38 and week 40. Two unintended losses occurred within three weeks after sampling (1.62%). Another additional unintended fetal death was notified at the 20-week screening ultrasonography. The total fetal-loss rate was 10.6%. In one case, talipes equinovarus was detected at the 20-week screening ultrasound study. CONCLUSIONS: Further studies are needed to determine the risk of amniotic leakage and its relation to duration of the procedure in patients undergoing early amnifiltration.

Prenatal detection of a paracentric inversion 16(q11.2q13).

We report the prenatal detection of an inherited paracentric inversion 16(q11.2q13).

Characterization of a heritable partial monosomy 18p by molecular and cytogenetic analysis.

This report describes the fourth case of heritable 18p monosomy, which was ascertained by prenatal diagnosis. Cytogenetic analysis of amniotic fluid cells by G-banding showed an apparently distal 18p chromosome deletion and a derivative X chromosome resulting from a translocation between the X and Y chromosomes. Analysis of peripheral blood lymphocytes from the parents by G-banding revealed the same chromosome 18 deletion in the mother, who did not have the X/Y translocation. Comparative genomic hybridization (CGH) studies confirmed the loss of chromosome region 18p11.3-pter previously detected, and eliminated the presence of unbalanced reorganizations of other chromosome regions. No subtle translocation was detected by fluorescence in situ hybridization (FISH) studies using whole chromosome specific painting probes. This is a new report of a heritable 18p monosomy. Although in our case the mother had several minor congenital malformations, the loss of 18p11.3 band was not associated with any obvious phenotypic alteration in the fetus.

Clinical application of multiplex quantitative fluorescent polymerase chain reaction (QF-PCR) for the rapid prenatal detection of common chromosome aneuploidies.

The clinical application of quantitative fluorescent polymerase chain reaction (QF-PCR) for rapid prenatal detection of chromosome aneuploidies has been limited in most studies to the detection of autosomal trisomies. Recently it has been shown that a newly identified highly polymorphic marker, termed X22, which maps to the Xq/Yq pseudoautosomal region of the sex chromosomes, used together with the X-linked short tandem repeat (STR) HPRT, allows the accurate detection of gonosome aneuploidies. We have developed a rapid assay, which includes these STR markers together with a sequence of the amelogenin region of the sex chromosomes and selected highly polymorphic autosomal STR. Two more X chromosome markers, as yet not used in previous QF-PCR applications, were also included in the assay. The molecular test was then used in a clinical trial on 551 uncultured amniotic fluid samples, allowing the assessment of copy number for chromosomes X, Y and 21 in 100% of cases. In the course of this study, two fetuses with Turner's syndrome and one with Klinefelter's syndrome were identified along with 17 autosomal trisomies. The assay proved to be so efficient and reliable that in most aneuploidy cases, in which ultrasound findings were in agreement with the molecular result, therapeutical interventions were possible without waiting for the result of cytogenetic analysis.

Bends in human mitotic metaphase chromosomes revisited: 15q11-13 is the most frequent non-random autosomal bend in blood cultures.

We have investigated the preferential bending of some chromosome sites in blood cultures from normal and chromosomally abnormal subjects. A total of 2,262 centromeric and 2,718 non-centromeric bends were recorded, and 69 non-centromeric sites were found not to bend at random. 15q11-13 bending was found to be the most frequent non-random autosomal bend. Bends on chromosomes may be remnants of a folded chromosome state in the nucleus, and may facilitate the preferential involvement of some chromosomal bands in structural reorganizations such as the isoacentric fragments, or contribute to the high frequency of interstitial deletions and isodicentric inversion duplications involving the 15q11-13 region.

Variegated aneuploidy related to premature centromere division (PCD) is expressed in vivo and is a cancer-prone disease.

We present three patients with variegated aneuploidy and premature centromere division (PCD), a rare chromosomal abnormality in humans. Comparison of these three and eight other patients with variegated aneuploidy related to PCD demonstrates a phenotype comprising most frequently microcephaly, CNS anomalies (with cerebellar affection and migration defects), mental retardation, pre-and postnatal growth retardation, flat and broad nasal bridge, apparently low-set ears, eye and skin abnormalities, and ambiguous genitalia in male patients. The occurrence of Wilms tumor in three patients, rhabdomyosarcoma in two others and acute leukemia in a fifth characterizes this condition as a chromosome or genome instability disorder with a high risk of malignancy. FISH studies in uncultured blood and buccal smear cells demonstrate that the random aneuploidies are not limited to cultured cells, but also occur in vivo.