17q21.31 Deletion

Below is a summary for 17q21.31 deletion syndrome or Koolen-de Vries syndrome observed in research publications. This is not meant to take the place of medical advice.

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What is 17q21.31 deletion syndrome or Koolen-de Vries syndrome?

17q21.31 deletion syndrome happens when a person is missing a piece of chromosome 17, one of the body’s 46 chromosomes. Chromosomes are structures in our cells that house our genes. The missing piece can affect learning and how the body develops.

17q21.31 deletion syndrome is also called Koolen-de Vries syndrome. This condition is caused by a deletion in the KANSL1 gene, which is missing when a person has a 17q21.31 deletion.


Because the 17q21.31 region is important for the proper function of the body’s cells, some people may have:

  • Developmental delay
  • Intellectual disability
  • Low muscle tone
  • Seizures
  • Undescended testicles in males
  • Heart or kidneys defects
  • Language issues and nasal voice
  • Very social behavior 
  • Anxiety
  • Feeding difficulty
  • Brain changes seen on magnetic resonance imaging (MRI)
  • Hip dislocation
  • Overly flexible joints
  • Rounding of the upper back
  • Sideways curvature of the spine, also called scoliosis

Do people who have 17q21.31 deletion syndrome look different?

People with 17q21.31 deletion syndrome may look different. Appearance can vary and can include some but not all of these features:

  • Long face
  • Pear-shaped nose with a round tip
  • Large ears
  • Opening between the eyelids that is narrow or slants upward
  • Drooping eyelids
  • A skin fold covering the inner corner of the eye
  • High forehead
  • Unusual hair texture
  • Smaller than average teeth size
  • Fewer number of teeth than average
  • Smaller than average head size
  • Short height

How many people have 17q21.31 deletion syndrome?

As of 2021, at least 100 children and adults with 17q21.31 deletion syndrome have been described in medical research. The oldest person known to date is 63 years old.


Support Resources



GeneReviews are a great resource to bring to your child’s clinicians. These publications provide a summary of current research on genetic conditions and information on ongoing care.

Check out the GeneReviews for 17q21.31 Deletions.


Research Article Summaries

We currently do not have any article summaries for 17q21.31 Deletion, but we add resources to our website as they become available.

The information available about 17q21.31 Deletion is limited, and families and doctors share a critical need for more information. As we learn more from children who have this gene change, we expect our list of resources and information to grow.

Full versions of published research articles can be found on PubMed. PubMed is a National Institutes of Health (NIH) online database that is free. It has a collection of both medical and scientific research articles. A PubMed search for 17q21.31 Deletion articles can be found here.


Research Opportunities

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Help the Simons Searchlight team learn more about 17q21.31 Deletion genetic changes by taking part in our research. You can learn more about the project and sign up here.


Family Stories

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