Cases reported "Chromosome Breakage"

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1/7. Jumping translocations involving 11q in a non-Hodgkin lymphoma.

    This paper presents the results of a cytogenetic analysis in an 11-year-old boy with non-Hodgkin lymphoma. The investigation was performed on slides obtained from short-term culture of lymph node cells. The analyses revealed an abnormal clone with loss of Y, gain of an X chromosome, t(3;22), trisomy 11, and three cytogenetically-related subclones with jumping translocations involving 11q13 as the common breakpoint region. This region is an unusual site of chromosome breakage in jumping translocations, and has not been reported thus far. Contrary to most published reports, the jumping translocation in our patient is associated with long survival.
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2/7. New chromosomal breakpoints in non-Hodgkin's lymphomas revealed by spectral karyotyping and G-banding.

    Chromosomal rearrangements in short term cultures from nine cases of non-Hodgkin's lymphomas (NHL) were characterized by G-banding, spectral karyotyping (SKY), and fluorescence in situ hybridization (FISH). Eight of the nine cases showed complex karyotypes with chromosomal aberrations which, in most cases, could not be fully characterized by traditional G-banding analysis alone. Karyotypic abnormalities of special interest were marker chromosomes and chromosomes with added unidentified chromosomal material, as previously non-identified chromosomal translocations were hidden behind these aberrations. SKY and FISH analysis, as a complement to banding analysis, significantly improved the karyotypes in seven of the nine cases and unveiled 21 previously unidentified rearrangements with novel translocation breakpoints. Traditional G-banding alone revealed seven new rearrangements, which were all confirmed by SKY. None of these new aberrations occurred as single clonal rearrangements but as parts of complex karyotypes. Nevertheless, the chromosomal break-point regions identified should be considered as potential hot spots for genes involved in the tumorigenesis of the malignancy.
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3/7. First non-mosaic case of isopseudodicentric chromosome 18 (psu idic(18)(pter --> q22.1::q22.1 --> pter) is associated with multiple congenital anomalies reminiscent of trisomy 18 and 18q- syndrome.

    Isopseudodicentric chromosome 18 is very rare and results in a combination of partial trisomy and partial monosomy of chromosome 18. We report here a hypotrophic newborn with a lateral cleft lip and palate and multiple craniofacial dysmorphisms, a combined heart defect, unilateral hypoplasia of the kidney, bilateral aplasia of thumbs, and generalized contractures. cytogenetic analysis revealed an isopseudodicentric chromosome 18 with breakpoint in 18q (46,XX,psu idic(18)(pter --> q22.1::q22.1 --> pter)). The isopseudodicentric chromosome 18 was observed in 100% of blood lymphocytes and umbilical cord fibroblasts, thus indicating a non-mosaic finding of the isopseudodicentric chromosome in the child. An elongated derivative chromosome 18 had also been found prenatally in amniotic cells. In contrast, a terminal deletion (18q-) was detected in placental cell cultures. The breakpoint was mapped to a 0.9 Mb region on 18q22.1 (located 64.8-65.7 Mb from the telomere of the p-arm) by a novel quantitative PCR approach with SYBR green detection. The results indicate an identical breakpoint of the isopseudodicentric chromosome 18 in the child and the 18q- chromosome in the placenta. To our knowledge this is the first report that a fetus carrying an isopseudodicentric chromosome 18 with breakpoint in 18q (46,XX,psu idic(18)(pter --> q22.1::q22.1 --> pter)) in non-mosaic form can be viable, but is associated with severe congenital malformations of the child.
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4/7. A patient with mutations in dna Ligase IV: clinical features and overlap with nijmegen breakage syndrome.

    The clinical phenotype of Ligase IV syndrome (LIG4 syndrome), an extremely rare autosomal recessive condition caused by mutations in the LIG4 gene, closely resembles that of nijmegen breakage syndrome (NBS), and is characterized by microcephaly, characteristic facial features, growth retardation, developmental delay, and immunodeficiency. We report a 4(1/2)-year-old boy who presented with acute T-cell leukemia. The facial gestalt was strongly reminiscent of NBS. The patient died shortly after the onset of treatment for his T-cell leukemia. Subsequent chromosome breakage studies showed a high rate of breakage in a fibroblast culture. Radiosensitivity was assessed by a colony survival assay; the results showed radiosensitivity greater than is typically seen in NBS. mutation screening of the NBS1 gene was negative. Sequencing of the LIG4 gene revealed a homozygous truncating mutation 2440 C>T (R814X). Although this mutation has been previously noted in LIG4 syndrome, this patient is the first reported homozygote for the mutation. In this study, we review the clinical features of this rare syndrome and provide suggestions for differential diagnosis.
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5/7. prenatal diagnosis of a de novo complex chromosome rearrangement (CCR) mediated by six breakpoints, and a review of 20 prenatally ascertained CCRs.

    OBJECTIVES: To describe the cytogenetic and FISH characterization of a prenatally diagnosed de novo complex chromosome rearrangement (CCR), showing the involvement of four chromosomes and six breakpoints, and review the literature concerning prenatally detected CCRs in order to obtain insights into addressing karyotype-phenotype correlations in prenatal genetic counseling. methods: Conventional protocols were used to set up cultures and chromosome preparations. Commercial and homemade probes were used for the FISH analyses. RESULTS: An apparently balanced de novo t(4;10;20) was prenatally identified by means of cytogenetic analysis. FISH revealed a rearrangement mediated by six breakpoints and the insertion of chromosome 8 material within the 4q region. The pregnancy was interrupted. The fetus showed malformations and anomalous cortical neuron migration. The assembled list of 20 prenatally detected CCRs points to the preferential involvement of chromosomes 4, 6 and 14. The involvement of chromosome 20 is described here for the first time. CONCLUSIONS: FISH analysis is essential for the accurate definition of a complex rearrangement. phenotype description of fetuses carrying CCRs investigated by means of molecular cytogenetic techniques may contribute to improving and personalizing genetic counseling in prenatal diagnosis.
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6/7. wiskott-aldrich syndrome in a family with fanconi anemia.

    thrombocytopenia may be the presenting finding for both wiskott-aldrich syndrome and fanconi anemia. We examined a sibship of four boys who had features of both of these hematologic disorders. Peripheral blood lymphocytes from three of the boys demonstrated dna instability when cultured with diepoxybutane, confirming the diagnosis of fanconi anemia in these patients. However, results of linkage analysis and x chromosome inactivation studies were consistent with the diagnosis of wiskott-aldrich syndrome in two of the boys, including one of the boys with fanconi anemia. These findings could be attributed to the occurrence of two rare genetic disorders in a single family or to an unusual variant of fanconi anemia. The recent identification of the Wiskott-Aldrich gene permitted us to address this question directly. Epstein-Barr virus-transformed cell lines from the two boys thought to have wiskott-aldrich syndrome on the basis of linkage analysis failed to express transcripts for the Wiskott-Aldrich gene. Genomic dna from these two patients demonstrated a G insertion in the tenth exon of the Wiskott-Aldrich gene, resulting in a frameshift and a premature stop codon. Surprisingly, the patient with fanconi anemia and a null mutation in the Wiskott-Aldrich gene had typical fanconi anemia but mild wiskott-aldrich syndrome.
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7/7. Differentiation of fanconi anemia from aplastic anemia by chromosomal breakage test.

    Aplastic anemia (AA) is a disorder of heterogeneous pathogenesis caused by diverse etiologies. fanconi anemia (FA) has the similar features of pancytopenia but is characterized by spontaneous or induced chromosomal instability and a variety of congenital anomalies. A cytogenetic breakage study is used to enable the diagnostic differentiation between FA and the so-called "idiopathic" AA. This method is based on the effect of the bifunctional alkylating agent mitomycin C (MMC) and alkylating mutagen diepoxybutane (DEB) on the chromosomes of peripheral lymphocytes in culture. Among thirty-three new cases of bone marrow failure with unknown etiologies, three young male patients were confirmed as victims of FA. The methodology and clinical manifestations were discussed. A prenatal screening was also performed to exclude the possibility of homozygous FA in one fetus at risk. The adequate dose of MMC used in our tests for diagnosis of FA were 20 ng/mL, while DEB did not work. These findings may suggest genetic diversity or other contributing factors in the pathogenesis of FA.
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