Mirror-symmetric duplicated chromosome 21q with minor proximal deletion, and with neocentromere in a child without the classical down syndrome phenotype

G. Barbi, I. Kennerknecht, G. Wöhr, D. Avramopoulos, G. Karadima, M. B. Petersen

Research output: Contribution to journalArticle

Abstract

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. (C) 2000 Wiley-Liss, Inc.

Original languageEnglish (US)
Pages (from-to)116-122
Number of pages7
JournalAmerican journal of medical genetics
Volume91
Issue number2
DOIs
StatePublished - Mar 16 2000
Externally publishedYes

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Keywords

  • Analphoid marker chromosome
  • Microdissection
  • Monosomy 21
  • Neocentromere
  • Trisomy 21

ASJC Scopus subject areas

  • Genetics
  • Genetics(clinical)

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