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)

Interpretación del polimorfismo en 15q11-13 en un caso de diagnóstico prenatal / Interpretation of polymorphic in 15q11-13 in a prenatal diagnosis case

La región del brazo largo del cromosoma 15(q11q13) es estructuralmente inestable. Más del 70 % de los pacientes con síndrome de Prader-Willi (PWS) y el 50 % de los pacientes con síndrome de Angelman (AS) presentan microdeleciones en esta zona. Presentamos un cromosoma 15 con un patrón de bandas G compatible con una deleción 15q11-13 observado en un diagnóstico prenatal citogenético en una gestante de 30 años referida por un TS patológico 1/196. La QF-PCR no presentó alteraciones. Debido a la existencia de un polimorfismo en la banda q11 que simula la deleción 15q11-13 realizamos una hibridación in situ para la región crítica de los síndromes PWS y AS, observándose dos copias de hibridación, descartando así la pérdida de material cromosómico relevante. El presente caso confirma una vez más que la detección de la deleción asociada a estos síndromes no es fiable por métodos citogenéticos convencionales, ya que existe un polimorfismo en la banda 15q11 que puede mimetizar la deleción de la banda 15q12

The proximal zone of the long arm of chromosome 15(q11q13) is a structurally unstable region of the genome, prone to breakage and rearrangement. The percentage of micro deletions associated with Prader-Willi syndrome (PWS) and Angelman syndrome (AS) is over 70 % for PWS and equal to 50 % for AS. We report a case of an abnormal-appearing chromosome 15 with a G-band pattern suggesting a deletion in 15q11-13 in amniotic fluid. The sample was from a 30-years-old woman referred for TS 1/196. We used fluorescent in situ hybridization probes specific for PWS/AS regiondue to the existence of a polymorphic band q11 that could be interpreted as a deletion of 15q11-13. All probes are present in tow copies, indicating that no deletion is present in this region. In conclusion, our case confirms that conventional cytogenetic methods are not useful to detect such deletions, due to it polymorphisms can exist in the 15q11 band that potentially mask a deletion of 15q12 band (AU)

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.

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.

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

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

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.

Cytogenetic and fluorescence in situ hybridization studies in four cases of plasma cell leukemia.

We present a cytogenetic and fluorescence in situ hybridization (FISH) study, using centromeric probes for chromosomes 3, 7, 11, and 18, TP53 gene (17p13), and RB-1 locus (13q14) DNA probes, in four cases of plasma cell leukemia (PCL). Among the four cases, three presented monosomy of the RB-1 locus and one monoallelic deletion of the TP53 gene. The present report shows the usefulness of the FISH technique to detect abnormalities not previously observed by conventional cytogenetics.

Dicentric (17;18) in a case of atypical B-cell chronic lymphocytic leukemia.

We report a new dic(17;18)(p11.2;p11.2) in a 61-year-old male patient diagnosed with atypical B-cell chronic lymphocytic leukemia. The dic(17;18)(p11.2;p11.2) was detected in 90%, 10%, and 100% of metaphases in the peripheral blood, bone marrow, and lymph node, respectively. Fluorescence in situ hybridization studies with chromosome 17 and 18 centromeric probes revealed the presence of two normal centromeres of both chromosomes 17 and 18. The centromere of one chromosome 17 was found together with the centromere of one chromosome 18, confirming the dicentric nature of the rearrangement. In addition, with the use of a 17p13.1 region probe, monosomy of the 17p13 region, where the Tp53 gene is located, was observed.

Application of cross-species color banding (RxFISH) in the study of T-prolymphocytic leukemia.

BACKGROUND AND OBJECTIVE: Cross-species color banding (RxFISH) is a new FISH technology based on the use of differentially labeled gibbon chromosome probes to obtain a specific color banding pattern for each human chromosome. The aim of the study was to test the RxFISH technique for better characterization of complex karyotypes in patients with T-prolymphocytic leukemia (T-PLL). DESIGN AND METHODS: The study evaluated the cross-species color banding technique in four patients affected with T-PLL previously studied by conventional cytogenetics. RESULTS: All patients showed an abnormal karyotype and three of them had a complex karyotype. The involvement of 14q11 in all four cases, the gain of 8q in three cases and a loss of chromosome 10, 15 and 17 and a gain of chromosome 21 in two cases were noted. The RxFISH technique identified from 2 to 7 not previously recognized aberrations per case and confirmed the inv(14)(q11q32). INTERPRETATION AND CONCLUSIONS: To our knowledge, this is the first application of RxFISH to characterize chromosomal rearrangements in T-cell neoplasms. RxFISH gave rapid and easy identification of chromosome rearrangements that were difficult to recognize by conventional cytogenetics. Using this new technology we identified 15 rearrangements not detected by conventional cytogenetics.

Translocation (11;14)(q13;q32) and preferential involvement of chromosomes 1, 2, 9, 13, and 17 in mantle cell lymphoma.

We have studied 13 cases of histologically confirmed mantle cell lymphomas (MCL) combining cytological-immunological features with conventional cytogenetics and in situ hybridization (ISH) techniques. Peripheral blood smears and lymph node biopsies expressed the typical mantle zone pattern with alpha B-cell phenotype. Most of the cases (11 of 13) had lymphomatous cells in the peripheral blood. Chromosome analysis was carried out on lymphoid cells from peripheral blood and/or lymph node biopsies. Phytohemagglutinin (PHA) and phorbol 12-myristate 13 acetate (TPA) were used as mitogens. Biotin-labeled libraries of whole chromosomes implicated in complex karyotypes were used to improve their interpretation. Clonal chromosome abnormalities were found in 10 of 13 patients (77%); 7 of these had a complex abnormality. The most frequent recurrent structural abnormalities were: t(11;14)(q13;q32), involvement of chromosome 1 (der[1], del[1], dup[1]), chromosome 2 (del[2], der[2]), chromosome 9 (der[9], -9), chromosome 13 (add[13], t[13q]), and chromosome 17 (add[17], der[17], t[17q]). The most frequent numerical abnormalities were monosomy 21 and loss of the Y chromosome.