Cases reported "Chromosome Aberrations"

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1/147. Increased sister chromatid exchange in bone marrow and blood cells from Bloom's syndrome.

    Bone-marrow cells from a patient with Bloom's syndrome cultured for 48 h in the presence of BudR exhibited a striking increase in the number of sister chromatid exchanges (SCEs) in comparison to that in the marrow cells of a patient with treated polycythemia vera (PV). Thus, it appears that an increased incidence of SCE in Bloom's syndrome occurs in various differentiated types of cells, not just blood lymphocytes, and constitutes the syndrome's most characteristic cytogenetic feature. In contrast, the incidence of SCE was not increased in marrow cells and lymphocytes of the particular PV patient studied here, whose cells did exhibit increased numbers of chromatid and chromosome gaps and breaks, presumably as result of the patient's earlier treatment. An increased frequency of SCE was demonstrated in Bloom's syndrome lymphocytes using both a technique based on BudR incorporation and one based on labeling with tritated deoxycytidine. This observation constitutes evidence against the increase of SCE being due to an unusual reaction to BudR. By conventional cytogenetic techniques, chromosome instability, including chromatid and chromosome breaks, but no homologous chromatid interchanges were also recognized in Bloom's syndrome bone-marrow cells incubated in vitro (without BudR) for either 1.k or 16 h. This observation points to the existence of chromosome instability in vivo.
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2/147. Constitutional chromosomal breakage.

    There were 18 individuals found to have a constitutional chromosome fragility causing an increase in break frequency. For each chromosome the breakpoint is always the same, whether it involves chromosomes from the same person, the same family, or different families. The fragile points are bands 10q24, 12q13, 16q21, 17p12, and Xq27. Autosomal constitutional fragility does not seem to have a phenotypic correspondence. They were found mostly in parents of children with chromosomal abnormalities or in couples with a history of repeated spontaneous abortions which permits one to raise the possibility of an interchromosomal effect. The six constitutional chromosomal fragilities of the x chromosome had in common the association of mental deficiency, delayed speech, and large malformed ears. The break points in constitutional chromosomal fragility were compared to those of spontaneous breaks in vitro, to those induced by x-rays, and to those in Fanconi's anemia. The theoretical consequences of these structural abnormalities are discussed as well as what to do about them when they are found.
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3/147. Screening for submicroscopic chromosome rearrangements in children with idiopathic mental retardation using microsatellite markers for the chromosome telomeres.

    Recently much attention has been given to the detection of submicroscopic chromosome rearrangements in patients with idiopathic mental retardation. We have screened 27 subjects with mental retardation and dysmorphic features for such rearrangements using a genetic marker panel screening. The screening was a pilot project using markers from the subtelomeric regions of all 41 chromosome arms. The markers were informative for monosomy in both parents at 3661902 loci (40.6%, 95% confidence interval 37.0-44.2%) in the 22 families where dna was available from both parents. In two of the 27 subjects, submicroscopic chromosomal aberrations were detected. The first patient had a 5-6 Mb deletion of chromosome 18q and the second patient had a 4 Mb deletion of chromosome 1p. The identification of two deletions in 27 cases gave an aberration frequency of 7.5% without adjustment for marker informativeness (95% confidence interval 1-24%) and an estimated frequency of 18% if marker informativeness for monosomy was taken into account. This frequency is higher than previous estimates of the number of subtelomeric chromosome abnormalities in children with idiopathic mental retardation (5-10%) although the confidence interval is overlapping. Our study suggests that in spite of the low informativeness of this pilot screening, submicroscopic chromosome aberrations may be a common cause of dysmorphic features and mental retardation.
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4/147. diagnosis of ataxia telangiectasia with the glycophorin A somatic mutation assay.

    There are no widely applied definitive laboratory tests for the diagnosis of ataxia telangiectasia (AT). We, and others, have previously reported significantly elevated levels of in vivo somatic mutation in blood samples from known AT patients, observations that might form the basis for a useful prospective laboratory test for confirmation of a clinical diagnosis of AT. In the present case, a 4 1/2-year-old black female was suspected of having AT based on ataxic gait and chronic upper respiratory infections. Blood work-up showed low IgG2 and elevated alpha-fetoprotein (AFP), consistent with the AT phenotype. Her peripheral blood karyotype was normal, however, with no spontaneous breakage observed among 100 solid stained metaphases. Lymphocytes from AT patients often show elevated levels of chromosome rearrangement, especially at sites of immunoglobulin and T-cell receptor genes. Therefore, a blood sample was analyzed with the glycophorin A (GPA) in vivo somatic mutation assay. The GPA assay detects and quantifies the phenotypically variant erythrocytes resulting from loss of heterozygosity for the MN blood group. The patient had a 10-fold increased frequency of variant erythrocytes with a phenotype consistent with simple loss of the N allele, which is characteristic of AT. In addition, the variant cell distribution for this patient showed three other, more qualitative hallmarks of AT: a normal frequency of allele loss and duplication events, a unique ridge of cells of intermediate phenotype between the normal and mutant peaks, and evidence of similar ongoing mutational loss of the M allele. Together with clinical data, these distinctive qualitative and quantitative features of the GPA assay allow for a diagnosis of AT with a projected accuracy of 95%. Therefore, we suggest that the GPA assay, which can be performed on < 1 ml of blood and completed in less than a day, be considered as a confirmatory laboratory test for a clinical diagnosis of AT.
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5/147. chromosome aberrations in bone marrow cells from Japanese patients with thorotrastosis.

    Exposure of bone marrow cells to alpha-particle radiation causes various types of chromosome abnormalities and hematological malignancies. We performed chromosome analysis of hematopoietic stem cells from the bone marrow of 52 Japanese patients with thorotrastosis and 21 age-matched controls. The frequency of cells with stable chromosome abnormalities was significantly higher in the patients with thorotrastosis. Further studies found 14 clonal chromosome aberrations in cells from 11 patients (21.2%); clones observed in the cells from 2 of these patients had high frequencies of chromosome abnormalities. In one case, 68 to 100% of the cells analyzed had a large partial loss in the short arm of chromosome 1 and a translocation between the short arms of chromosomes 2 and 3 [46,XY,1p-,t(2p ;3p-)]. The cells from the other patient contained a clone with partial loss of both the short and long arms of chromosome 5 (46,XX,5p-,5q-). The frequency of this clone has been constant for the last 15 years (6-24%). We also analyzed bone marrow mononuclear cells from 17 of the patients for mutations of the TP53 tumor suppressor gene (formerly known as p53). However, no mutation was found in any of the cells, including those from the 2 patients with abnormal clones. Moreover, repeated medical examinations showed no evidence of leukemia or myelodysplasia in these patients. Our study suggests that exposure of bone marrow cells to alpha-particle radiation may induce clonal chromosomal aberrations at a high frequency.
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6/147. Two complex translocations in chronic granulocytic leukemia involving chromosomes 22, 9, and a third chromosome.

    Among 13 Ph-positive cases of chronic granulocytic leukemia (CGL), banding studies revealed two with complex rearrangements involving translocation of the long arm of number 22 to another autosome and a segment of that chromosome translocated to the long arm of number 9. In a patient with both CGL and sickle cell anemia, the 3-way rearrangement involved chromosomes 5, 9, and 22; and he also had a second philadelphia chromosome and two constitutional variants: pericentric inversion of the other number 9 chromosome and satellite polymorphism in the G group. The karyotype of the leukemic cells was interpreted as: 47,XY,inv(9) (p11q13),t(5;9;22)(q13;q34;q11) del(22)(q11). In the second patient, the complex translocation in the Ph-positive cells involved chromosomes 3, 9, and 22, resulting in a karyotype interpreted as: 46,XX,t(3;9;22)(p21;q34;q11). Several reports indicate that an abnormality of chromosome 9 is not essential for the development of Ph-positive CGL, but the very high frequency of its involvement (including these unusual translocations) suggests that some type of non-random somatic association may exist between 9q and 22q which makes simultaneous breakage likely. Attempts to correlate specific types of pH chromosome rearrangements with the clinical course of CGL must await the identification of more cases and longer follow-up.
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7/147. Morphologically normal, CD30-negative b-lymphocytes with chromosome aberrations in classical Hodgkin's disease: the progenitor cell of the malignant clone?

    A recent study observed that numerical chromosome abnormalities in Hodgkin's disease (HD) are detected not only in morphologically abnormal Hodgkin/reed-sternberg cells, but also in a fraction of morphologically normal cells. However, the phenotypic constitution of these genetically abnormal, morphologically normal cells and their relationship to the malignant Hodgkin/reed-sternberg cells could not be established in the earlier cases studied, because of the low frequency of these cells. The present study investigated two cases of classical Hodgkin's disease containing a relatively large population of such apparently normal cells with aberrant chromosome copy numbers. The phenotype and their position within the developmental route of the malignant compartment were examined by a combined in situ hybridization and immunocytochemistry approach. Numerical abnormalities for chromosome 1 in one case and for chromosomes X, Y, and 1 in the other case were observed not only in CD30-positive Hodgkin/reed-sternberg cells, but also in CD30-negative, morphologically normal cells. It was shown that these genetically aberrant cells expressed the B-cell antigen CD19, thus confirming their B-cell nature. These studies indicate a relationship between the genome aberrations in these genetically abnormal, morphologically normal B-cells and the Hodgkin/reed-sternberg cells, suggesting that they are progenitor cells of the malignant cell fraction.
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8/147. A Dutch family with progressive sensorineural hearing impairment linked to the DFNA2 region.

    We studied a Dutch family with DFNA2-linked progressive sensorineural hearing impairment (SNHI). Recent audiograms were obtained from 18 of the affected persons (age 7-81 years) and were used in a gene-linkage analysis. Linear regression analysis of the audiograms, using binaural mean thresholds, disclosed on average a descending slope of approximately 10 dB/octave at any age and an annual threshold increase at any frequency of about 0.7 dB/year. There may have been substantial congenital impairment at higher frequencies, but longitudinal analysis of hearing impairment in the youngest case, who was followed from age 5 years, suggested that the most significant changes in hearing may have occurred in the first two decades of life. Linkage analysis was carried out with special attention to the DFNA2 region because hearing trends were very similar to families previously linked to DFNA2. Linkage to DFNA2 was established with maximum lod scores of 4.7 and 3.2 for the flanking markers of the DFNA2 region (D1S432;MYCL1).
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9/147. Reciprocal translocations as an indicator for radiation exposures in the low dose range.

    A few years back, the frequency of dicentrics was determined shortly after exposure in five accidentally exposed radiation workers. In all cases the observed dicentric yield was significantly higher in comparison with the background level, and the resulting estimated whole body doses lay between 0.2 and 0.3 Gy. Now, a number of years later (1 to 11 years), the frequency of translocations has been determined by means of the FISH technique. chromosomes 2, 4 and 8 were painted. The measured translocation frequency lay, however, within the range of the spontaneous variation between individuals. No radiation exposure could, therefore, be proven. In two further cases, the dicentrics were determined by means of the conventional Giemsa staining technique, and the translocations by means of chromosome painting carried out on the same blood samples, which were taken about 3 and 10 years, respectively, after the radiation exposure. The dose estimates obtained on the basis of dicentric frequency using the Qdr method, and on the basis of FISH detected translocations, are compared.
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10/147. Deletion - translocation del (12) (p11) leads to (t10;12) (p13;pII).

    Renewed examinatinon with improved banding techniques of a boy previously reported to have the karyotype 46, XY,del(12)(p11) revealed a translocation 46, XY,t(10;12)(p13;p11), and reexamination of a boy previously reported to have the karyotype 46,XY/46,XY,del(5)(p13) showed the same mosaicism, but with a significantly lower frequency of cells with del(5)(p13), 8% compared with 23% at the time of birth. The decrease of the frequency of cells with chromosome abnormality in mixoploids during the first years of life as found in the present case as well as in prevously reported cases is discussed.
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