Cases reported "Trisomy"

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1/117. trisomy 20p resulting from inverted duplication and neocentromere formation.

    Normal human centromeres contain large tandem arrays of alpha-satellite dna of varying composition and complexity. However, a new class of mitotically stable marker chromosomes which contain neocentromeres formed from genomic regions previously devoid of centromere activity was described recently. These neocentromeres are fully functional yet lack the repeat sequences traditionally associated with normal centromere function. We report here a supernumerary marker chromosome derived from the short arm of chromosome 20 in a patient with manifestations of dup(20p) syndrome. Detailed cytogenetic, FISH, and polymorphic microsatellite analyses indicate the de novo formation of the marker chromosome during meiosis or early postzygotically, involving an initial chromosome breakage at 20p11.2, followed by an inverted duplication of the distal 20p segment due to rejoining of sister chromatids and the activation of a neocentromere within 20p12. This inv dup(20p) marker chromosome lacks detectable centromeric alpha-satellite and pericentric satellite III sequences, or centromere protein CENP-B. Functional activity of the neocentromere is evidenced by its association with 5 different, functionally critical centromere proteins: CENP-A, CENP-C, CENP-E, CENP-F, and INCENP. Formation of a neocentromere on human chromosome 20 has not been reported previously and in this context represents a new mechanism for the origin of dup(20p) syndrome.
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2/117. Maternal uniparental isodisomy for chromosome 14 detected prenatally.

    Maternal uniparental disomy (UPD) for chromosome 14 (upd(14)mat) has been associated with a distinct phenotype. We describe the first case of maternal uniparental isodisomy for chromosome 14 detected prenatally, in a pregnancy with mosaicism for trisomy 14 observed in both a chorionic villus sample (CVS) and in amniocytes. Detailed analysis of polymorphic microsatellites showed that the fetus was essentially isodisomic for one of the mother's chromosomes 14 and that recombination had introduced a mid-long arm region of heterodisomy. The fetus, which died in utero at 18 weeks, showed no apparent pathological features. The case demonstrates for the first time a maternal meiosis II non-disjunction of chromosome 14 leading to a trisomic conception which has been incompletely corrected by 'rescue' in the early embryo.
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3/117. Severe intra-uterine growth retardation in a patient with maternal uniparental disomy 22 and a 22-trisomic placenta.

    We report on a maternal uniparental disomy of chromosome 22 in a patient with severe intra-uterine growth retardation. Karyotyping of a placental tissue revealed non-mosaic trisomy 22, whereas lymphocyte chromosomes from the newborn were normal 46,XY. Microsatellite analysis using dna extracted from white blood cells showed maternal uniparental heterodisomy for chromosome 22. Thus, the conceptus started as maternal trisomy due to meiotic non-disjunction, and trisomy rescue occurred subsequently through loss of the paternal homologue resulting in maternal uniparental disomy. Normal phenotypes in previous reports have suggested that maternal UPD 22 has no impact on the phenotype. Thus, growth retardation in this patient was probably caused by dysfunction of the trisomic placenta.
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4/117. Molecular cytogenetic characterization of a prenatally detected supernumerary minute marker chromosome 8.

    The characterization of a prenatally detected very small (approximately half of 18p-(karyotype: 47,XX, mar[16]/46,XX[7]) supernumerary marker chromosome (SMC) identified by GTG-banding analysis is described. The marker has been identified as derived from chromosome 8 centromeric material using a combination of different cytogenetic (GTG-, NOR-, CBG banding), molecular cytogenetic (24 colour-fluorescent in situ hybridization [FISH], three-colour FISH using centromeric probes for all human chromosomes) and molecular genetic techniques (microsatellite analysis). This is the first case described with such a minute SMC derived from chromosome 8 diagnosed prenatally, the 15th case reporting on a SMC originating from chromosome 8 and the third such case without any severe clinical features.
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5/117. Recombinant balanced and unbalanced translocations as a consequence of a balanced complex chromosomal rearrangement involving eight breakpoints in four chromosomes.

    We report on a family with a balanced complex chromosomal rearrangement (CCR) involving eight breakpoints between chromosomes 6, 7, 18, and 21 in the father. All three sons inherited one derivative chromosome from the father and in addition each inherited a different recombinant chromosome resulting in a partial trisomy 6q in the first, an apparently balanced karyotype in the second, and a partial trisomy 7q in the third son. fluorescence in situ hybridisation (FISH) and microsatellite analysis were essential for the identification of the breakpoints. In addition, the results were confirmed by a 24-colour FISH experiment using the spectral karyotyping (SKYtrade mark) system. Paternal origin of the de novo CCR in the father was demonstrated for the first time by haplotype analysis. This is the second report of a CCR leading to simpler but unbalanced translocations in offspring as a consequence of recombination during gametogenesis, and the first report of a family case of CCR exhibiting as many as eight breakpoints in the transmitting carrier. The initial prediction that viable offspring would be quite unlikely had to be revised after the birth of three children. Genetic counselling of carriers of balanced complex rearrangements has to consider a higher probability for unbalanced recombinations than has been so far commonly assumed.
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6/117. Dicentric marker derived from chromosome 22 associated with mild clinical signs: a case report.

    amniocentesis performed after 24 weeks' gestation following ultrasonographic diagnosis of isolated unilateral hydronephrosis showed a de novo extra structurally abnormal chromosome in all cells examined. A combination of conventional and molecular cytogenetic techniques characterized the supernumerary marker as a dicentric and bisatellited marker derived from chromosome 22. At birth the infant presented hypoplasia of the right kidney, hearing loss on the left side and bilateral preauricular pits and skin tags. At three years, growth and neurological development were normal.
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7/117. trisomy of the long arm of chromosome 1 resulting in a dicentric derivative (6)t(1;6) chromosome in a child with myelodysplastic syndrome following treatment for a primitive neuroectodermal tumor.

    We report the clinical, hematologic, and cytogenetic findings for a child with secondary myelodysplastic syndrome (MDS) after treatment for a primitive neuroectodermal tumor. At the time of conversion to MDS, conventional cytogenetics revealed an unbalanced der(6)t(1;6) that resulted in trisomy of the long arm of chromosome 1 and partial monosomy and duplication of 6p. Using alpha satellite probes, fluorescence in situ hybridization of bone marrow cells showed that the rearranged chromosome contained the centromeres of both chromosomes 1 and 6, thus forming a dic(1;6) resulting in trisomy 1q. This report is the first to describe a case of childhood secondary myelodysplastic syndrome associated with a trisomy 1q involving chromosome 6.
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8/117. Mirror-symmetric duplicated chromosome 21q with minor proximal deletion, and with neocentromere in a child without the classical down syndrome phenotype.

    We report on a mentally retarded child with multiple minor anomalies and an unusually rearranged chromosome 21. This der(21) chromosome has a deletion of 21p and of proximal 21q, whereas the main portion of 21q is duplicated leading to a mirror-symmetric appearance with the mirror axis at the breakpoint. The centromere is only characterized by a secondary constriction (with a centromeric index of a G chromosome) at an unexpected distal position, but fluorescence in situ hybridization (FISH) with either chromosome specific or with all human centromeres alpha satellite dna shows no cross hybridization. Thus, the marker chromosome represents a further example of an "analphoid marker with neocentromere." Molecular analysis using polymorphic markers on chromosome 21 verified a very small monosomic segment of the proximal long arm of chromosome 21, and additionally trisomy of the remaining distal segment. Although trisomic for almost the entire 21q arm, our patient shows no classical down syndrome phenotype, but only a few minor anomalies found in trisomy 21 and in monosomy of proximal 21q, respectively.
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9/117. A partial trisomy 15q due to 15;17 translocation detected by conventional cytogenetic and FISH techniques.

    We report a case having multiple abnormalities including the simultaneous presence of the heart defect and central nerve system abnormalities, which has been reported in a few cases, and with a partial trisomy 15q. Partial trisomy 15q has been inherited from a balanced translocation carried by his phenotypically normal father, detected by traditional banding and fluorescence in situ hybridization (FISH). Application of FISH using whole chromosome specific library probes, locus specific and repetitive probes allowed us to detect the translocation between chromosomes 15q and 17q. Simultaneous application of probes revealed the position of the translocation. Interestingly, in addition to the chromosomes 15 pericentromeric signals, the use of chromosome 15 beta-satellite III probe demonstrated an extra signal on chromosome 14 in both metaphase, and lighted three signals interphase nuclei which was inherited from his father. This patient is compared with other partial trisomy 15q patients reported in the literature. The results are also discussed in relation to genetic counselling for the possible relation of chromosome abnormality and clinical findings.
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10/117. Fibrous tumors in children - a morphologic and interphase cytogenetic analysis of problematic cases.

    We describe and discuss the findings by fluorescent in situ hybridization (FISH) for detection of non-random chromosomal gains, in a group of unusual fibrous lesions in children. Nuclear disaggregation was used to prepare slides from eight cases which were hybridized using alpha-satellite enumeration probes for chromosomes 8, 11 and 17. trisomy 8 and 11 were detected in a high percentage of nuclei in cases of congenital/infantile fibrosarcomas (ranging from 45 to 80%), and in a low grade fibrosarcoma in an older child (23%). Only gains of chromosome 17 were detected in a case of infantile fibromatosis (22%). In this study we have found that given the unconventional histopathologic features, the detection of more than one non-random chromosomal gains by FISH, may aid in further defining fibrous tumors in children, and may be useful as an ancillary diagnostic test in the future.
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