Below is a summary for the SOX11 gene observed in research publications. This is not meant to take the place of medical advice.

What is SOX11 Syndrome?

SOX11-related syndrome happens when there are changes to the SOX11 gene. These changes can keep the gene from working as it should. This syndrome is also known as Coffin-Siris syndrome type 9.

Key Role

The SOX11 gene plays a key role in the growth of brain cells.


Because the SOX11 gene is important in the development and function of brain cells, many people who have SOX11-related syndrome have:

  • Small head size, also known as microcephaly
  • Intellectual disability
  • Speech delay
  • Slow growth
  • Changes to the fingers and toes, such as underdeveloped nails
  • Certain facial features, such as a wide mouth and thick lips

People who have changes in the SOX11 gene may have a condition called Coffin-Siris syndrome type 9, or CSS9. Coffin-Siris syndrome is caused by changes in several different genes: ARID1A, ARID1B, ARID2, DPF2, SMARCA4, SMARCB1, SMARCC2, SMARCD1, SMARCE1, SOX4, and SOX11. 


There is overlap among the symptoms of each type of Coffin-Siris syndrome. Please see the Coffin-Siris syndrome gene guide for more information. People who have SOX11-related syndrome typically have intellectual disability and may or may not have changes in physical appearance.

Do people who have SOX11- syndrome look different?

People who have SOX11-related syndrome may look different. Appearance can vary and can include some but not all of these features:

  • Wide mouth
  • Thick lips
  • Small head size, also called microcephaly
  • Curved fingers or an underdeveloped fifth finger
  • Webbed toes

Speech delay is common.



Developmental delay is common.



Some people have autism.



Support Resources

Coffin-Siris Syndrome Foundation:


Research Article Summaries


Research Opportunities

Simons Searchlight

Help the Simons Searchlight team learn more about SOX11 genetic changes by taking part in our research. You can learn more about the project and sign up here.


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