16p11.2 Deletion Syndrome
What is 16p11.2 deletion syndrome?
16p11.2 deletion syndrome happens when a person is missing a piece of chromosome 16, 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.
Key Role
Genes within the 16p11.2 region are important for brain development and function.
Symptoms
Because the 16p11.2 region is important in brain activity, many people who have 16p11.2 deletion syndrome have:
- Developmental delay
- Behavioral issues
- Motor speech and language difficulties
- Obesity
- Autism or features of autism
- Seizures
- Motor coordination challenges
What causes 16p11.2 deletion syndrome?
16p11.2 deletion syndrome is a genetic condition, which means that it is caused by variants in genes. Our genes contain the instructions, or code, that tell our cells how to grow, develop, and work. Every child gets two copies of the 16p11.2 gene: one copy from their mother’s egg, and one copy from their father’s sperm. In most cases, parents pass on exact copies of the gene to their child. But the process of creating the egg or sperm is not perfect. A change in the genetic code can lead to physical issues, developmental issues, or both.
Sometimes a spontaneous variant happens in the sperm, egg or after fertilization. When a brand new genetic variant happens in the genetic code is called a ‘de novo’ genetic variant. The child is usually the first in the family to have the genetic variant.
De novo variants can take place in any gene. We all have some de novo variants, most of which don’t affect our health. But because 16p11.2 plays a key role in development, de novo variants in this gene can have a meaningful effect.
Research shows that 16p11.2 deletion syndrome is often the result of a de novo variant in 16p11.2. Many parents who have had their genes tested do not have the 16p11.2 genetic variant found in their child who has the syndrome. In some cases, 16p11.2 deletion syndrome happens because the genetic variant was passed down from a parent.
Autosomal dominant conditions
16p11.2 deletion syndrome is an autosomal dominant genetic condition. This means that when a person has the one damaging variant in 16p11.2 they will likely have symptoms of 16p11.2 deletion syndrome. For someone with an autosomal dominant genetic syndrome, every time they have a child there is a 50 percent chance they pass on the same genetic variant and a 50 percent chance they do not pass on the same genetic variant.
Autosomal Dominant Genetic Syndrome
Why do I or my child have 16p11.2 deletion syndrome?
No parent causes their child’s 16p11.2 deletion syndrome. We know this because no parent has any control over the chromosome changes that they do or do not pass on to their children. Please keep in mind that nothing a parent does before or during the pregnancy causes this to happen. The genetic change takes place on its own and cannot be predicted or stopped.
What are the chances that other family members or future children will have 16p11.2 deletion syndrome?
Each family is different. A geneticist or genetic counselor can give you advice on the chance that this will happen again in your family.
The risk of having another child who has 16p11.2 deletion syndrome depends on the genes of both biological parents.
- If neither biological parent has the same genetic variant found in their child, the chance of having another child who has the syndrome is on average 1 percent. This 1 percent chance is higher than the chance of the general population. The increase in risk is due to the very unlikely chance that more of the mother’s egg cells or the father’s sperm cells carry the same genetic variant.
- If one biological parent has the same genetic variant found in their child, the chance of having another child who has the syndrome is 50 percent.
For a symptom-free brother or sister of someone who has 16p11.2 deletion syndrome, the sibling’s risk of having a child who has 16p11.2 deletion syndrome depends on the sibling’s genes and their parents’ genes.
- If neither parent has the same genetic variant causing 16p11.2 deletion syndrome, the symptom-free sibling has a nearly 0 percent chance of having a child who would inherit 16p11.2 deletion syndrome.
- If one biological parent has the same genetic variant causing 16p11.2 deletion syndrome, the symptom-free sibling has a 50 percent chance of also having the same genetic variant. If the symptom-free sibling has the same genetic variant, their chance of having a child who has the genetic variant is 50 percent.
For a person who has 16p11.2 deletion syndrome, the risk of having a child who has the syndrome is about 50 percent.
How many people have 16p11.2 deletion syndrome?
As of 2024, at least 230 people with 16p11.2 deletion syndrome have been identified in a medical clinic.
Do people who have 16p11.2 deletion syndrome look different?
People who have 16p11.2 deletion syndrome may look different. Appearance can vary and can include some but not all of these features:
- Larger than average head size
- Smaller than average nose and chin
How is 16p11.2 deletion syndrome treated?
Scientists and doctors have only just begun to study 16p11.2 deletion syndrome. At this point, there are no medicines designed to treat the syndrome. A genetic diagnosis can help people decide on the best way to track the condition and manage therapies. Doctors can refer people to specialists for:
- Physical exams and brain studies
- Genetics consults
- Development and behavior studies
- Other issues, as needed
A developmental pediatrician, neurologist, or psychologist can follow progress over time and can help:
- Suggest the right therapies. This can include physical, occupational, speech, or behavioral therapy.
- Guide individualized education plans (IEPs).
Specialists advise that therapies for 16p11.2 deletion syndrome should begin as early as possible, ideally before a child begins school.
If seizures happen, consult a neurologist. There are many types of seizures, and not all types are easy to spot. To learn more, you can refer to resources such as the Epilepsy Foundation’s website: epilepsy.com/…t-is-epilepsy/seizure-types
This section includes a summary of information from major published articles and the Simons Searchlight quarterly registry report. It highlights how many people have different symptoms. To learn more about the articles, see the Sources and References section of this guide.
Behavior and development concerns linked to 16p11.2 deletion syndrome
Behavior and development concerns linked to 16p11.2 deletion syndrome
The typical 16p11.2 deletion region is also known as the breakpoint (BP) BP4-BP5 region, and depending on the person’s deletion, breakpoints may have up to about 30 genes removed.
Some of the information below is compiled from the Simons Searchlight registry.
Speech and Learning
Many people with 16p11.2 deletion syndrome had developmental delay or intellectual disability, as well as language delays.
- 149 out of 239 people had developmental delay or intellectual disability (63 percent)
- 166 out of 239 people had language delays (70 percent)
Behavior
Fewer than one-half of people with 16p11.2 deletion syndrome had features of autism, and some had ADHD.
- 104 out of 239 people had features of autism (44 percent)
- 68 out of 239 people had ADHD (29 percent)
Brain
Some people with 16p11.2 deletion syndrome had seizures in infancy or childhood. Age range for the first seizure was between newborn and 14 years old. Most people tended to have their first seizure by the age of 18 months. The most common seizure types were focal seizures or tonic-clonic seizures.
- 56 out of 239 people had seizures (23 percent)
- 19 out of 31 people had seizure onset before 1 year of age (61 percent)
Some people had a head size that was larger than average, also called macrocephaly. Some people had abnormal brain changes seen on magnetic resonance imaging (MRI).
- 68 out of 239 people had macrocephaly (29 percent)
- 9 out of 30 people had abnormal MRI findings (30 percent)
Medical and physical concerns linked to 16p11.2 deletion syndrome
Mobility
People who have 16p11.2 deletion syndrome had low muscle tone.
- 137 out of 239 people had low muscle tone (57 percent)
Feeding and digestion
People with 16p11.2 deletion syndrome most often had constipation, diarrhea, or GERD.
- 61 out of 239 people had constipation (26 percent)
- 33 out of 239 people had diarrhea (14 percent)
- 80 out of 239 people had GERD (34 percent)
Where can I find support and resources?
16p11.2 Genetic Foundation
A patient advocacy organization with the goal of providing support, promoting research, and championing hope for those affected by 16P11.2 Deletion Syndrome.
Simons Searchlight
Simons Searchlight is an online international research program, building an ever growing natural history database, biorepository, and resource network of over 175 rare genetic neurodevelopmental disorders. By joining their community and sharing your experiences, you contribute to a growing database used by scientists worldwide to advance the understanding of your genetic condition. Through online surveys and optional blood sample collection, they gather valuable information to improve lives and drive scientific progress. Families like yours are the key to making meaningful progress. To register for Simons Searchlight, go to the Simons Searchlight website at www.simonssearchlight.org and click “Join Us.”
- Learn more about Simons Searchlight: www.simonssearchlight.org/frequently-asked-questions
- Simons Searchlight webpage with more information on 16p11.2 deletion: www.simonssearchlight.org/research/what-we-study/16p11-2-deletion
- Simons Searchlight Facebook group: https://www.facebook.com/groups/1439358376210852
Sources and References
The content in this guide comes from published studies about 16p11.2 deletion syndrome. Below you can find details about each study, as well as links to summaries or, in some cases, the full article.
- Moufawad El Achkar, C., Rosen, A., Kessler, S. K., Steinman, K. J., Spence, S. J., Ramocki, M., Marco, E. J., Green Snyder, L., Spiro, J. E., … Sherr, E. H. (2022). Clinical characteristics of seizures and epilepsy in individuals with recurrent deletions and duplications in the 16p11.2 region. Neurology Genetics, 8(5), e200018. https://pubmed.ncbi.nlm.nih.gov/36531974/
- Simons Searchlight registry update April 2024. https://cdn.simonssearchlight.org/wp-content/uploads/2024/04/16044343/16p11.2-deletion-23Q4-24Q1.pdf
- Taylor C. M., Smith R., Lehman C., Mitchel, M. W., Singer, K., Weaver, W. C., & Chung, W. 16p11.2 recurrent deletion. 2021 Oct 28. In: Adam MP, Feldman J, Mirzaa GM, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2024. Available from: https://www.ncbi.nlm.nih.gov/books/NBK11167/
- Qiu, Y., Arbogast, T., Lorenzo, S. M., Li, H., Tang, S. C., Richardson, E., Hong, O., Cho, S., Shanta, O., … Sebat, J. (2019). Oligogenic effects of 16p11.2 copy-number variation on craniofacial development. Cell Reports, 28(13), 3320-3328.e3324. https://pubmed.ncbi.nlm.nih.gov/31553903/
- Vos, N., Kleinendorst, L., van der Laan, L., van Uhm, J., Jansen, P. R., van Eeghen, A. M., Maas, S. M., Mannens, M., & van Haelst, M. M. (2024). Evaluation of 100 Dutch cases with 16p11.2 deletion and duplication syndromes; from clinical manifestations towards personalized treatment options. European Journal of Human Genetics. https://pubmed.ncbi.nlm.nih.gov/38605127/