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Genetic and Rare Diseases Information Center (GARD)

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Trisomy 17 mosaicism

Other Names for this Disease
  • Chromosome 17 duplication
  • Chromosome 17 trisomy
  • Chromosome 17, trisomy
  • Chromosome 17, trisomy mosaicism
  • Trisomy 17
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Trisomy 17 mosaicism is a chromosomal abnormality in which there are three copies of chromosome 17 in some cells of the body, rather than the usual two copies. Trisomy 17 mosaicism is one of the rarest trisomies in humans. It is often incorrectly called trisomy 17 (also referred to as full trisomy 17), which is when three copies of chromosome 17 are present in all cells of the body. Full trisomy 17 has never been reported in a living individual in the medical literature.[1] Few cases of trisomy 17 mosaicism have been described, most having been detected during pregnancy through a test called amniocentesis.[2] Only a few individuals have had a confirmed diagnosis of trisomy 17 mosaicism after birth. Because the proportion and location of cells with trisomy 17 differs from case to case, the presence and severity of signs and symptoms may vary significantly from person to person.
Last updated: 5/8/2013


  1. Hassold T. Mosaic trisomies in human spontaneous abortions. Hum Genet. 1982;
  2. Utermann B, Riegel M, Leistritz D, Karall T, Wisser J, Meisner L et al. Pre- and Postnatal Findings in Trisomy 17 Mosaicism. Am J Med Genet Part A. 2006;
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Basic Information

  • The National Human Genome Research Institute, part of the National Institutes of Health (NIH), has developed a fact sheet on chromosome abnormalities, which may be helpful to you. To read this information, visit the link.

    MedlinePlus, the National Library of Medicine Web site designed to direct you to information and resources that help you research your health questions, provides further information about chromosomes. Click on the link.

In Depth Information

  • Orphanet is a European reference portal for information on rare diseases and orphan drugs.  Access to this database is free of charge.
  • PubMed is a searchable database of medical literature and lists journal articles that discuss Trisomy 17 mosaicism. Click on the link to view a sample search on this topic.