5p Deletion Syndrome
5p deletion syndrome is also called Cri-du-chat syndrome. For this webpage, we will be using the name 5p deletion syndrome to encompass the wide range of variants observed in the people identified.
What is 5p deletion syndrome?
5p deletion syndrome happens when a person has an extra piece of chromosome 5, 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.
People with 5p deletion syndrome tend to have their own unique set of breakpoints. This means that there is large variability between each person’s genetic region and their medical features.
Symptoms
Because genes in the 5p region are important in brain development and function, many people who have 5p deletion syndrome have:
- Developmental delay
- Intellectual disability
- Speech delay
- Hearing loss
- Brain changes seen on magnetic resonance imaging (MRI)
- Heart defects at birth
- Attention-deficit/hyperactivity disorder (ADHD)
- Autism
- Aggressive behaviors
- Low muscle tone
- Stiff walking
- A tendency to hurt themselves
- Feeding issues and constipation
- A high-pitched cry that might sound like a cat
What causes 5p deletion syndrome?
5p 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 5p 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 5p plays a key role in development, de novo variants in this gene can have a meaningful effect.
Research shows that 5p deletion syndrome is often the result of a de novo variant in 5p. Many parents who have had their genes tested do not have the 5p genetic variant found in their child who has the syndrome. In some cases, 5p syndrome happens because the genetic variant was passed down from a parent.
Autosomal dominant conditions
5p deletion is an autosomal dominant genetic condition. This means that when a person has the one damaging variant in 5p they will likely have symptoms of 5p 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 5p deletion syndrome?
No parent causes their child’s 5p 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 5p 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 5p 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 5p deletion syndrome, the sibling’s risk of having a child who has 5p deletion syndrome depends on the sibling’s genes and their parents’ genes.
- If neither parent has the same genetic variant causing 5p deletion syndrome, the symptom-free sibling has a nearly 0 percent chance of having a child who would inherit 5p deletion syndrome.
- If one biological parent has the same genetic variant causing 5p 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 5p deletion syndrome, the risk of having a child who has the syndrome is about 50 percent.
How many people have 5p deletion syndrome?
As of 2026, over 500 people with 5p deletion syndrome have been described in medical research. Cri-du-chat syndrome happens in about 1 in 15,000 to 1 in 50,000 births.
Do people who have 5p deletion syndrome look different?
People with 5p deletion syndrome may look different. Appearance can vary and can include, but is not limited to, these features:
- Lower than average muscle tone
- Smaller than average head size and height
- Misaligned teeth
- Smaller than average jaw size
- Short distance between the lip and the upper lip and the nose
- Wide-set eyes
- Skin folds of the upper eyelids that cover the inner corner of the eye
- Prominent bridge of the nose
- Premature gray hair
How is 5q35 deletion syndrome treated?
Scientists and doctors have only just begun to study 5p 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 5p 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 5p deletion syndrome
Learning and speech
People with 5p deletion syndrome had developmental delay or intellectual disability, and speech and language impairment.
- 297 out of 299 people had intellectual disability (99 percent)
Behavior
Some people with 5p deletion syndrome had behavioral issues, such as features of autism and attention-deficit/hyperactivity disorder (ADHD).
Brain
People with 5p deletion syndrome had neurological medical issues, such as having a small head size (microcephaly), low muscle tone (hypotonia), and brain changes seen on magnetic resonance imaging (MRI). Both prenatal and postnatal brain changes were seen on MRI, such as cerebellar hypoplasia, corpus callosum underdevelopment or defects, defects of cortical development and neuronal migration, frontoparietal polymicrogyria, deficient myelination, or reduced cerebral white matter volume.
- 280 out of 291 people had microcephaly (96 percent)
- 146 out of 254 people had hypotonia (58 percent)
- 9 out of 36 people had brain changes on MRI (25 percent)
Medical and physical concerns linked to 5p deletion syndrome
Vision
Many people with 5p deletion syndrome had vision issues, including wide-set eyes, and crossed eyes (strabismus).
- 302 out of 384 people had wide-set eyes (79 percent)
- 137 out of 260 people had strabismus (53 percent)
Other medical features
Some people with 5p deletion syndrome had a high-pitched, cat-like cry and a sideways curve of the spine, also called scoliosis. Some people had a heart defect, such as ventricular septal defect.
- 411 out of 434 people had a high-pitched cry (95 percent)
- 23 out of 50 people had scoliosis (46 percent)
- 3 out of 36 people had ventricular septal defect (8 percent)
Where can I find support and resources?
5p Minus Society
The 5p Minus Society aims to maximize quality of life for individuals with 5p- and their families.
Cri du Chat Research Foundation
The Cri du Chat Research Foundation drives innovative research to develop therapies that transform the lives and independence of everyone affected by 5p- 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 5p deletion: www.simonssearchlight.org/research/what-we-study/5p-deletion
- Simons Searchlight Facebook group: https://www.facebook.com/groups/5p-deletion
Sources and References
- Ajitkumar, A., Jamil, R. T., & Mathai, J. K. Cri Du Chat syndrome. 2022 Oct 25. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2026 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK482460/
- Almeida, V. T., Chehimi, S. N., Gasparini, Y., Nascimento, A. M., Carvalho, G. F. S., Montenegro, M. M., Zanardo É, A., Dias, A. T., Assunção, N. A., … & Kulikowski, L. D. (2023). Cri-du-Chat syndrome: Revealing a familial atypical deletion in 5p. Molecular Syndromology, 13(6), 527-536. doi:10.1159/000524371
- Su, J., Fu, H., Xie, B., Lu, W., Li, W., Wei, Y., Zhang, Q., Wei, S., Chen, Q., … & Qin, Z. (2019). Prenatal diagnosis of cri-du-chat syndrome by SNP array: Report of twelve cases and review of the literature. Molecular Cytogenetics, 12, 49. doi:10.1186/s13039-019-0462-0
- Wright, R., Burrill, N., Crane, H., Khalek, N., Gebb, J., Bach, A. M., Whitehead, M. T., Zarnow, D., Oliver, E., … & Moldenhauer, J. S. (2025). Case series of prenatally diagnosed Cri du Chat syndrome with associated magnetic resonance imaging findings. Pediatric Neurology, 169, 93-97. doi:10.1016/j.pediatrneurol.2025.05.014
- Vanneste, M., Matthews, H., Sleyp, Y., Hammond, P., Shriver, M., Weinberg, S. M., Marazita, M. L., Walsh, S., Hallgrimsson, B., … & Peeters, H. (2026). Advancing genotype-phenotype analysis through 3D facial morphometry: Insights from Cri-du-Chat syndrome. J Med Genet, 63(2), 95-102. doi:10.1136/jmg-2025-110940