What is Koolen De Vries Syndrome / 17q21.31 Microdeletion Syndrome

Koolen-de Vries syndrome (KdVS), also known as 17q21.31 microdeletion syndrome, is a rare genetic condition caused by the deletion or mutation of the KANSL1 gene. It is characterized by developmental delays, intellectual disability, distinctive facial features, and a friendly, social personality.

What causes Koolen-de Vries syndrome?

Koolen-de Vries syndrome is primarily caused by a small deletion of genetic material on chromosome 17 at the q21.31 position or a mutation within the KANSL1 gene. This gene is crucial for normal development, as it helps regulate the activity of many other genes. While most cases occur sporadically (de novo), meaning they are not inherited from parents, the condition fundamentally alters early neurodevelopment.

How common is Koolen-de Vries syndrome?

The exact prevalence of Koolen-de Vries syndrome is estimated to be between 1 in 16,000 and 1 in 55,000 live births. Because the condition is often underdiagnosed due to variable symptom presentation, these numbers may be conservative. Currently, 8 individuals with Koolen-de Vries syndrome have connected through the DiseaseMaps.org platform to share their experiences and support one another.

What are the primary symptoms and affected systems?

The clinical presentation of Koolen-de Vries syndrome is diverse, often affecting multiple organ systems. Common features include:

• Neurological: Global developmental delay, moderate intellectual disability, and speech impairment.


• Physical: Distinctive facial features (such as a high forehead and pear-shaped nose), hypotonia (low muscle tone), and skeletal anomalies.


• Organ involvement: Approximately 30-50% of patients may experience congenital heart defects, kidney issues, or epilepsy.


• Behavioral: Individuals with Koolen-de Vries syndrome are frequently noted for their social, cheerful, and cooperative temperament.

How is Koolen-de Vries syndrome diagnosed?

Diagnosis is confirmed through genetic testing, typically a chromosomal microarray (CMA) to detect the deletion or gene sequencing to identify mutations in the KANSL1 gene. Early diagnosis is vital for accessing appropriate early intervention therapies and specialized medical support.

Next steps

• Consult with a clinical geneticist to discuss testing and family planning.


• Schedule evaluations with pediatric specialists, including cardiologists and neurologists.


• Connect with the DiseaseMaps.org community to share experiences with other families living with Koolen-de Vries syndrome.


• Engage with early intervention services, such as speech, occupational, and physical therapy.

Medical disclaimer: This information is for educational purposes only and should not replace professional medical advice, diagnosis, or treatment.

References

• NIH Genetic and Rare Diseases Information Center (GARD): 17q21.31 microdeletion syndrome overview.


• Orphanet: Rare disease database entry for Koolen-de Vries syndrome.


• OMIM (Online Mendelian Inheritance in Man): KANSL1 gene and associated syndrome data.


• Koolen-de Vries Syndrome Foundation: Patient-focused clinical resources and support.