Koolen de Vries Syndrome

What is Koolen de Vries syndrome?

Koolen de Vries Sydrome (KdVS) occurs when there is a variation on chromosome 17. This is caused by either a KANSL1 gene mutation or a microdeletion of 17q21.31 (which includes the KANSL1 gene). This particular gene is used to help regulate how genes are expressed and is found in most tissues within the body, therefore has an important role in development.1


Ongoing work?

Our team are currently studying speech and language abilities in children with KdVS. Please contact the geneticsofspeech@mcri.edu.au to learn more about this study. We would love to have your involvement.

Phone: (03) 9936 6334


For further information contact:

For further information, do get in touch with the CRE Speech and Language research team at:

Email: geneticsofspeech@mcri.edu.au

Phone: (03) 9936 6334



Frequently asked questions

Research has shown that 100% of individuals that have been included in studies with KdVS have speech and language difficulties. Individuals often present with oral hypotonia (low tone) and apraxia within their infant and preschool years.2 In the later school and teenage years, the apraxia is less prominent and speech is often characterised by dysarthria. Those with KdVS have strengths in their social communication, and often have a great desire to communicate.

There are a range of associated health and developmental conditions that those with KdVS may experience.

The following have been found in > 75% of cases; 3

  • Distinctive facial features
  • Hypotonia (low tone)
  • Developmental delay
  • Intellectual disability
  • Speech and language delay
  • Friendly/amiable disposition


It has also been noted that gross and fine motor skills, nonverbal cognitive impairment, seizures, joint hypermobility and feeding difficulties (chewing and drooling) are common, however drooling has been reported to resolve by early school years. 2 Hearing loss has also been associated in a handful of children, yet this is not a common characteristic of KdVS.

A most recent study has shown that speech is often typically delayed with first words sometimes not achieved until 3 years of age. 2  It was also reported that children showed minimal or no babbling in the first six months of life. 2

Childhood apraxia of speech (CAS) is a common feature for individuals with KdVS, particularly in the early years. They often had difficulty with oral motor movements such as reduced and range of jaw movement, rounding of lips (e.g. blowing a kiss or bubble) and tongue movement. 2 Older individuals were also found to have dysarthria, characterised by flaccid slow speech, low pitch, hypernasality, monotone and loudness.2 Expressive and receptive language difficulties have also been reported in a majority of participants examined to date.2

As mentioned above, younger children typically present with CAS, and as this resolves, dysarthria is more prominent. A recent study reported that all preschool children used either sign language, gesture or an assistive device to supplement their communication needs in the early years.2 The study also found that improvement in the individual’s speech intelligibility (ability to be understood by others) only occurred after explicit teaching of speech with intensive speech pathology input. 2

One study has reported on this area. The study found that 39% of children with KdVS attended a mainstream school, with support, whilst 61% attended schools for children with additional needs.2

There is no research on speech and language interventions that are specifically designed for individuals with KdVS. Currently, interventions are specific to an individual’s needs and goals and require a speech pathologist to ensure that current best-evidenced based therapies are implemented.

A recent study has mentioned that improvement was shown in speech intelligibility when the participants were explicitly taught sound imitation, syllable generation and combinations, complex words, short phrases, sentences and spontaneous speech. 2 They also noted that there should be a focus on general language and literacy development alongside speech motor skills. 2

For information and support on Koolen de Vries Syndrome: https://kdvsfoundation.org 

For information and support on childhood apraxia of speech: https://www.apraxia-kids.org 


  1. Genetics Home Reference. (2019). KANSL1 gene. Retrieved
  2. Morgan, A.T., Haaften, L.V., van Hulst, K., Edley, C., Mei, C., Tan, T.Y., Amor, D., Fisher, S.E., & Koolen D.A. (2018). Early speech development in Koolen de Vries syndrome limited by oral praxis and hypotonia. European Journal of Human Genetics, 26(1), 75-84.
  3. Koolen, D., Morgan, A., de Vries, B.A. (2019). Koolen-de Vries Syndrome. GeneReviews.

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