Down Syndrome

  • Charles J. Epstein
Part of the Readings from the Encyclopedia of Neuroscience book series (REN)


Down syndrome is the set of physical, mental, and functional abnormalities that result from trisomy 21, the presence in the genome of three rather than the normal two chromosomes 21. The physical abnormalities that together give rise to the distinctive facial appearance associated with this condition include upslanting palpebral fissures with inner epicanthic folds, flatness of the bridge of the nose, midfacial hypoplasia, and a tendency to protrude the tongue, especially when very young. Many other functionally inconsequential minor abnormalities of the ears, hands, and feet may also be present, and stature is generally reduced. Approximately 40% of affected individuals are born with congenital heart disease, with endocardial cushion and related septal defects frequently being present. Obstruction of the intestinal tract also occasionally occurs during development. Although trisomy 21 is the autosomal trisomy most compatible with survival through the period of gestation, only about a third of affected embryos and fetuses are actually liveborn.

Further reading

  1. Epstein CJ (1986): The Consequences of Chromosome Imbalance: Principles, Mechanisms, and Models. New York: Cambridge University PressCrossRefGoogle Scholar
  2. Pueschel SM, Rynders JE, eds (1982): Down Syndrome: Advances in Biomedicine and the Behavioral Sciences. Cambridge: Ware PressGoogle Scholar
  3. Scott BS, Becker LE, Petit TL (1983): Neurobiology of Down’s syndrome. Prog Neurobiol 21: 199–237CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 1989

Authors and Affiliations

  • Charles J. Epstein

There are no affiliations available

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