Down Syndrome: Symptoms & Signs

  • Medical Author:
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

Medically Reviewed on 1/9/2019

Down syndrome is a genetic disorder and a common chromosome abnormality in humans, in which an embryo contains extra genetic material from chromosome 21. These extra genes and DNA cause changes in development of the embryo and fetus leading to both physical and mental abnormalities. Not every patient with Down syndrome will have all the signs and symptoms or have symptoms and signs with the same degree of severity. Some characteristic signs and symptoms include intellectual disability, a small head, short neck, a flat face, upward slanting eyes, flat, low-set ears, and a protruding tongue.

Causes of Down syndrome

The most common cause of Down syndrome is trisomy 21, where the embryo gets three copies of chromosome 21, instead of two. Translocation describes a less common cause of Down syndrome in which an extra piece of chromosome 21 attaches to another chromosome.


"Down Syndrome." National Down Syndrome Society. <>.

Medically Reviewed by a Doctor on 1/9/2019

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