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Findings that shed new light on the possible pathogenesis of a disease or an adverse effect
Familial 4.3 Mb duplication of 21q22 sheds new light on the Down syndrome critical region
  1. Anne Ronan1,
  2. Kerry Fagan2,
  3. Louise Christie1,
  4. Jeffrey Conroy3,
  5. Norma J Nowak3,4,
  6. Gillian Turner1
  1. 1
    Hunter Genetics Unit, Waratah, New South Wales, Australia
  2. 2
    Department of Cytogenetics, Hunter Area Pathology Service, New Lambton, New South Wales, Australia
  3. 3
    Microarray and Genomics Facility, Cancer Prevention and Population Sciences, Roswell Park Cancer Institute, Buffalo, New York, USA
  4. 4
    Center of Excellence in Bioinformatics and Life Sciences, University at Buffalo, Buffalo, New York, USA
  1. Anne Ronan, aronan{at}


A 4.3 Mb duplication of chromosome 21 bands q22.13–q22.2 was diagnosed by interphase fluorescent in situ hybridisation (FISH) in a 31 week gestational age baby with cystic hygroma and hydrops; the duplication was later found in the mother and in her 8-year-old daughter. All had the facial gestalt of Down syndrome (DS). This is the smallest accurately defined duplication of chromosome 21 reported with a DS phenotype. The duplication encompasses the gene DYRK1 but not DSCR1 or DSCAM. Previous karyotype analysis and telomere screening of the mother, and karyotype analysis and metaphase FISH of a chorionic villus sample, had all failed to reveal the duplication. The findings in this family add to the identification and delineation of a “critical region” for the DS phenotype on chromosome 21.

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  • Competing interests: none.

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