Atypical Down syndrome and partial trisomy 21

Jenkins, Edmund C.; Duncan, Charlotte J.; Wright, Chris; Wilbur, Lorraine; Wisniewski, K. E.; Sklower, Susan L.; French, J. H.; Jones, C.; Brown, W. Ted

doi:10.1111/j.1399-0004.1983.tb02219.x

Cited by 17 publications

References 12 publications

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Tertiary trisomy due to a reciprocal translocation of chromosomes 5 and 21 in a four-generation family

et al. 2000

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Tertiary trisomy, or double trisomy, is a rare occurrence. We present two individuals with a previously unreported tertiary trisomy for chromosomes 5p and 21q in an eight-generation pedigree. Their phenotypes are compared with other partial trisomies of either 5p or 21q from the literature. The propositus was diagnosed with trisomy 21 at 2 years of age after a karyotype study for short stature and developmental delay. His phenotype was described as atypical for Down syndrome. He presented at 9 years of age because of pervasive behavioral problems and obesity. He was brachycephalic with a flattened nasal bridge, but he lacked other characteristics of trisomy 21. Because of lack of phenotypic evidence of Down syndrome, a repeat karyotype was obtained and showed 47,XY, +der(21)t(5;21)(p15.1; q22.1), incorporating partial trisomies of both chromosomes 5 and 21. Mother had a balanced translocation, 46, XX,t(5;21)(p15.1; q22.1); 8 other relatives were examined. The translocation originated from the maternal great-grandmother, but only the propositus and his mentally retarded aunt had a similar phenotye and the derivative chromosome. Fluorescence in situ hybridization showed absence of band 21q22.2 in the derivative chromosome of the propositus and his aunt, indicating that neither had trisomy for the Down syndrome critical region. These cases represent a unique double partial trisomy of chromosome arms 5p and 21q that occurred because of 3:1 malsegregation of a reciprocal translocation. These cases further demonstrate that phenotypic discordance with cytogenetic results dictate further investigation using advanced cytogenetic hybridization.

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Tertiary trisomy due to a reciprocal translocation of chromosomes 5 and 21 in a four-generation family

et al. 2000

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Down syndrome critical region around D21S55 on proximal 21q22.3

et al. 2005

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We have analysed the DNA of 2 patients with many manifestations of Down syndrome and partial duplication of distinct regions of chromosome 21, respectively, q11.205→q22.300 and q22.300→qter (Rahmani et al.: Proceedings of the National Academy of Sciences of the United States of America 86:5958–5962, 1989). Assessment of the copy number of five chromosome 21 sequences (SODI, D21S17, D21S55, ETS2, and D21S15) has shown that D21S55 was duplicated in both cases. The size of the common duplicated region can be estimated between 400 and 3,000 Kb, after the results of pulsed‐field gel analysis and from the knowledge of regional mapping of the probes D21S17, D21S55, and ETS2. This region, located on the proximal part of 21q22.3,is postulated to contain genes the overexpression of which plays a major role in the pathogenesis of Down syndrome.

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Analysis of human chromosome 21: correlation of physical and cytogenetic maps; gene and CpG island distributions.

et al. 1990

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Human chromosome 21 has been analyzed by pulsed‐field gel electrophoresis using somatic cell hybrids containing limited regions of the chromosome and greater than 60 unique sequence probes. Thirty‐three independent NotI fragments have been identified, totalling 43 million bp. This must account for essentially the entire long arm, and therefore gaps remaining in the map must be small. The extent of the pulsed‐field map has allowed the direct correlation of the physical map with the cytogenetic map: translocation breakpoints can be unambiguously positioned along the long arm and the distances between them measured in base pairs. Three breakpoints have been identified, providing physical confirmation of cytogenetic landmarks. Information on sequence organization has been obtained: (i) 60% of the unique sequence probes are located within 11 physical linkage groups which can be contained in only 20% of the long arm; (ii) 9/21 genes are clustered within 4%; (iii) translocation breakpoints appear to occur within CpG island regions, making their identification difficult by pulsed‐field techniques. This analysis contributes to the human genome mapping effort, and provides information to guide the rapid investigation of the biology of chromosome 21.

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Atypical Down syndrome and partial trisomy 21

Cited by 17 publications

References 12 publications

Tertiary trisomy due to a reciprocal translocation of chromosomes 5 and 21 in a four-generation family

Tertiary trisomy due to a reciprocal translocation of chromosomes 5 and 21 in a four-generation family

Down syndrome critical region around D21S55 on proximal 21q22.3

Analysis of human chromosome 21: correlation of physical and cytogenetic maps; gene and CpG island distributions.

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