15q15 Deletion Syndrome
What is 15q15deletion syndrome?
15q15 deletion syndrome happens when a person is missing a 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 15q15 region are important for brain development and function.
Symptoms
Because the 15q15 region is important for the proper function of the brain, some people may have:
- Intellectual disability
- Developmental delay
- Low muscle tone
- Gastrointestinal reflux and feeding issues
- Sideways curve of the spine, also called scoliosis
- Brain changes seen on magnetic resonance imaging (MRI)
- Minor genital defects
- Vision issues
- Speech difficulties
- Learning difficulties
What causes 15q15 deletion syndrome?
15q15 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 15q15 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 15q15 plays a key role in development, de novo variants in this gene can have a meaningful effect.
Research shows that 15q15 deletion syndrome is often the result of a de novo variant in 15q15. Many parents who have had their genes tested do not have the 15q15 genetic variant found in their child who has the syndrome. In some cases, 15q15 deletion syndrome happens because the genetic variant was passed down from a parent.
Autosomal dominant conditions
15q15 deletion syndrome is an autosomal dominant genetic condition. This means that when a person has the one damaging variant in 15q15 they will likely have symptoms of 15q13.3 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 does my child have a change in the 15q15 gene?
No parent causes their child’s 15q15 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 15q15 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 15q15 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 15q15 deletion syndrome, the sibling’s risk of having a child who has 15q15 deletion syndrome depends on the sibling’s genes and their parents’ genes.
- If neither parent has the same genetic variant causing 15q15 deletion syndrome, the symptom-free sibling has a nearly 0 percent chance of having a child who would inherit 15q15 deletion syndrome.
- If one biological parent has the same genetic variant causing 15q15 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 15q15 deletion syndrome, the risk of having a child who has the syndrome is about 50 percent.
How many people have 15q15 deletion syndrome?
As of 2025, about 10 people with 15q15 deletion syndrome have been identified in medical research.
Do people who have 15q15 deletion syndrome look different?
People with 15q15 deletion syndrome may look different. Appearance can vary and can include some but not all of these features:
- Beaked or noticeable nose
- Small lower jaw
- Thin upper lip
- Long slender fingers
- Thin body type and tall height
How is 15q15deletion syndrome treated?
Scientists and doctors have only just begun to study 15q15 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 15q15 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 15q15 deletion syndrome
People with 15q15 deletion syndrome have been identified in the Unique rare disease organization. People usually had a larger deletion that included the 15q15 chromosome region to 15q22.
In 2025, the Simons Searchlight registry had 0 people with 15q15 deletion syndrome. As more people register and share medical information, we will be able to share more information with the 15q15 deletion community.
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 15q15 deletion: www.simonssearchlight.org/research/what-we-study/15q15-deletion
- Simons Searchlight Facebook group: https://www.facebook.com/groups/15q15deletion
Sources and References
The content in this guide comes from published studies about 15q15 deletion syndrome. Below you can find details about each study.
- Unique genetic guide for 15q deletions: https://www.rarechromo.org/media/information/Chromosome%2015/15q%20deletions%20FTNW.pdf