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GTR Home > Conditions/Phenotypes > Complete trisomy 21 syndrome

Summary

Down syndrome, the most frequent form of mental retardation caused by a microscopically demonstrable chromosomal aberration, is characterized by well-defined and distinctive phenotypic features and natural history. It is caused by triplicate state (trisomy) of all or a critical portion of chromosome 21. [from OMIM]

Clinical features

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Practice guidelines

  • NSGC, 2021
    National Society of Genetic Counselors Position Statement: Prenatal Cell-Free DNA Screening
  • ACMG ACT, 2021
    American College of Medical Genetics and Genomics Noninvasive Prenatal Screening via Cell-Free DNA ACT Sheet, Trisomy 21/Down syndrome: Positive Cell Free DNA Screen, 2021

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