15q11.2 BP1-BP2 Deletion Syndrome
15q11.2 BP1-BP2 deletion syndrome is also called Burnside-Butler syndrome or 15q11.2 BP1-BP2 microdeletion syndrome. For this webpage, we will be using the name 15q11.2 BP1-BP2 deletion syndrome to encompass the wide range of variants observed in the people identified.
What is 15q11.2 BP1-BP2 deletion syndrome?
15q11.2 BP1-BP2 deletion syndrome happens when a person has a missing piece of chromosome 15, 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 15q11.2 BP1-BP2 deletion region are important for brain development and function.
Symptoms
Because genes in the 15q11.2 BP1-BP2 deletion region are important in brain development and function, some people who have 15q11.2 BP1-BP2 deletion syndrome have:
- Developmental delay
- Intellectual disability
- Language delay
- Memory issues
- Lower than average muscle tone
- Seizures
- Brain changes seen on magnetic resonance imaging (MRI)
What causes 15q11.2 BP1-BP2 deletion syndrome?
15q11.2 BP1-BP2 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 15q11.2 BP1-BP2 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 15q13.3 plays a key role in development, de novo variants in this gene can have a meaningful effect.
Research shows that 15q11.2 BP1-BP2 deletion syndrome is often the result of a de novo variant in 15q11.2 BP1-BP2. Many parents who have had their genes tested do not have the 15q11.2 BP1-BP2 genetic variant found in their child who has the syndrome. In some cases, 15q11.2 BP1-BP2 deletion syndrome happens because the genetic variant was passed down from a parent.
Autosomal dominant conditions
15q11.2 BP1-BP2 deletion syndrome is an autosomal dominant genetic condition. This means that when a person has the one damaging variant in 15q11.2 BP1-BP2 they will likely have symptoms of 15q11.2 BP1-BP2 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 15q11.2 BP1-BP2 deletion syndrome?
No parent causes their child’s 15q11.2 BP1-BP2 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 15q11.2 BP1-BP2 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 15q11.2 BP1-BP2 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 15q11.2 BP1-BP2 deletion syndrome, the sibling’s risk of having a child who has 15q11.2 BP1-BP2 deletion syndrome depends on the sibling’s genes and their parents’ genes.
- If neither parent has the same genetic variant causing 15q11.2 BP1-BP2 deletion syndrome, the symptom-free sibling has a nearly 0 percent chance of having a child who would inherit 15q11.2 BP1-BP2 deletion syndrome.
- If one biological parent has the same genetic variant causing 15q11.2 BP1-BP2 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 15q11.2 BP1-BP2 deletion syndrome, the risk of having a child who has the syndrome is about 50 percent.
How many people have 15q11.2 BP1-BP2 deletion syndrome?
As of 2025, over 800 people with 15q11.2 BP1-BP2 deletion syndrome have been described in medical research. Many people who have the 15q11.2 BP1-BP2 deletion do not have medical features.
Do people who have 15q11.2 BP1-BP2 deletion syndrome look different?
People who have 15q11.2 BP1-BP2 deletion syndrome may look different from others. Appearance can vary among people who have the syndrome. One study of almost 150 people found that about 40 percent had changes in facial features. This included a broad forehead, an unusual ear shape, and changes to the roof of the mouth, also called the palate.
How is 15q11.2 BP1-BP2 deletion syndrome treated?
Scientists and doctors have only just begun to study 15q11.2 BP1-BP2 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 15q11.2 BP1-BP2 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. 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 15q11.2 BP1-BP2 deletion syndrome
Learning and speech
Some people with 15q11.2 BP1-BP2 deletion syndrome had developmental delay or intellectual disability, and speech impairment.
- 192 out of 421 people had developmental delay or intellectual disability (46 percent)
- 145 out of 214 people had speech impairment (68 percent)
Behavior
People with 15q11.2 BP1-BP2 deletion syndrome had behavioral issues, such as autism, attention-deficit/hyperactivity disorder (ADHD), self-injury behavior, and aggression.
- 81 out of 143 people had behavioral issues (57 percent)
- 108 out of 765 people had autism (14 percent)
- 51 out of 148 people had ADHD (34 percent)
Brain
People with 15q11.2 BP1-BP2 deletion syndrome had neurological medical issues, such as a smaller than average head size (microcephaly), seizures, brain changes seen on magnetic resonance imaging (MRI), lower than average muscle tone (hypotonia), and movement challenges.
- 43 out of 490 people had microcephaly (9 percent)
- 119 out of 795 people had seizures (15 percent)
- 59 out of 116 people had brain changes seen on MRI (51 percent)
- 74 out of 468 people had hypotonia (16 percent)
Where can I find support and resources?
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 15q11.2 BP1-BP2 deletion: www.simonssearchlight.org/research/what-we-study/15q11-2-BP1-BP2-deletion
- Simons Searchlight Facebook group: https://www.facebook.com/groups/15q11.2-bp1-bp2-deletion
Sources and References
- Basarir, G., Erdogan, I., Ozyilmaz, B., Gencpinar, P., & Dundar, N. O. (2025). Beyond the copy number differences: The phenotypic diversity of children with 15q11.2 microdeletions and microduplications. Journal of Child Neurology, 40(9), 784-793. doi:10.1177/08830738251366862