GENE GUIDE

MYT1L-Related Syndrome

This guide is not meant to take the place of medical advice. Please consult with your doctor about your genetic results and health care choices. This Gene Guide was last updated on 2024. As new information comes to light with new research we will update this page. You may find it helpful to share this guide with friends and family members or doctors and teachers of the person who has MYT1L-Related Syndrome.
a doctor sees a patient

MYT1L-related syndrome is also called intellectual developmental disorder, autosomal dominant 39. For this webpage, we will be using the name MYT1L-related syndrome to encompass the wide range of variants observed in the people identified.

MYT1L-related syndrome happens when there are changes to the MYT1L gene. These changes can keep the gene from working as it should.

Key Role

The MYT1L gene plays a key role in the development of the brain.

Symptoms

Because the MYT1L gene is important for brain activity, many people who have MYT1L-related syndrome have:

  • Motor and speech delay
  • Mild to moderate intellectual disability
  • Excessive hunger and obesity that begins early in life
  • Behavioral challenges, including hyperactivity, autism spectrum disorder, and aggression
  • Lower than average muscle tone

MYT1L-related 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 MYT1L 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 MYT1L plays a key role in development, de novo variants in this gene can have a meaningful effect.

Research shows that MYT1L-related syndrome is often the result of a de novo variant in MYT1L. Many parents who have had their genes tested do not have the MYT1L genetic variant found in their child who has the syndrome. In some cases, MYT1L-related syndrome happens because the genetic variant was passed down from a parent.

Autosomal dominant conditions

MYT1L-related syndrome is an autosomal dominant genetic condition. This means that when a person has the one damaging variant in MYT1L they will likely have symptoms of MYT1L-related 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

GENE / gene
GENE / gene
Genetic variant that happens in sperm or egg, or after fertilization
GENE / gene
Child with de novo genetic variant
gene / gene
Non-carrier child
gene / gene
Non-carrier child

Why does my child have a change in the MYT1L gene?

No parent causes their child’s MYT1L-related syndrome. We know this because no parent has any control over the gene 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 gene change takes place on its own and cannot be predicted or stopped.

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 MYT1L-related 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 MYT1L-related syndrome, the sibling’s risk of having a child who has MYT1L-related syndrome depends on the sibling’s genes and their parents’ genes.

  • If neither parent has the same genetic variant causing MYT1L-related syndrome, the symptom-free sibling has a nearly 0 percent chance of having a child who would inherit MYT1L-related syndrome.

As of 2024, at least 88 people with MYT1L-related syndrome have been identified in a medical clinic. The first case of MYT1L-related syndrome was described in 2015. Scientists expect to find more people who have the syndrome as access to genetic testing improves.

People who have MYT1L-related syndrome may look different. Appearance can vary and can include some but not all of these features:

  • Long chin
  • Nose that has a broad base and tip
  • Large mouth
  • Narrow eyes
  • Square-shaped trunk

Scientists and doctors have only just begun to study MYT1L-related 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 MYT1L-related 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: www.epilepsy.com/learn/types-seizures.

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.

Speech and Learning

People with MYT1L-related syndrome had intellectual disability, and many had language delays or impairment. Not all people with MYT1L-related syndrome had intellectual disability: some people had only learning difficulties. Most people had motor and/or fine motor delays.

  • 41 out of 50 people had intellectual disability (82 percent)
  • 58 out of 61 people had language delays or impairment (95 percent)
  • 9 out of 50 people had learning difficulties without intellectual disabilities (18 percent)
82%
41 out of 50 people had intellectual disability.
95%
58 out of 61 people had language delays or impairment.
18%
9 out of 50 people had learning difficulties without intellectual disabilities.

Behavior

Many people with MYT1L-related syndrome had behavioral challenges, such as autism or features of autism, attention-deficit/hyperactivity disorder (ADHD), aggressive behavior, anxiety, repetitive movements or sounds, and cheerful behavior. Some people had repetitive movements without having an autism diagnosis.

  • 58 out of 61 people had behavioral challenges (95 percent)
  • 26 out of 61 people had autism or features of autism (43 percent)
  • 25 out of 61 people had ADHD (41 percent)
  • 26 out of 61 people had aggressive behavior (43 percent)
  • 12 out of 61 people had anxiety (20 percent)
  • 26 out of 61 people had repetitive movements or sounds (43 percent)
  • 9 out of 61 people had cheerful behavior (15 percent)
43%
26 out of 61 people had autism or features of autism.
41%
25 out of 61 people had ADHD.
43%
26 out of 61 people had aggressive behavior.
20%
12 out of 61 people had anxiety.
43%
26 out of 61 people had repetitive movements or sounds.
15%
9 out of 61 people had cheerful behavior.

Brain

Some people with MYT1L-related syndrome had seizures, brain changes on magnetic resonance imaging (MRI), and a smaller than average head size, also called microcephaly. But, some people had a larger than average head size, also called macrocephaly.

  • 15 out of 61 people had seizures (25 percent)
  • 13 out of 45 people had brain changes seen on MRI (29 percent)
  • 5 out of 56 people had microcephaly (9 percent)
  • 4 out of 56 people had macrocephaly (7 percent)
Human head showing brain outline

Weight issues

People with MYT1L-related syndrome were at risk of developing obesity and had eating behavior disorders. Common eating behavior disorders included an inability to feel full and eating rapidly.

  • 36 out of 62 people were overweight or obese (58 percent)
  • 22 out of 62 people were obese (36 percent)
  • 28 out of 61 people had eating behavior disorders (46 percent)
58%
36 out of 62 people were overweight or obese.
36%
22 out of 62 people were obese.
46%
28 out of 61 people had eating behavior disorders.

Other findings

Some people with MYT1L-related syndrome had sleep difficulties, lower than average muscle tone, and vision issues. A few people had short height, a hormone disorder, or lipid changes in their blood. Hormone disorders included Hashimoto’s thyroiditis, pituitary stem disorders with low prolactin, hypogonadism, and episodes of high and low blood pressure.

  • 18 out of 58 people had sleep issues (31 percent)
  • 31 out of 57 people had lower than average muscle tone (54 percent)
  • 21 out of 57 people had vision issues (38 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.”

Sources and References

The content in this guide comes from published studies about MYT1L-related syndrome. Below you can find details about each study, as well as links to summaries or, in some cases, the full article.

  • De Rocker N. et al. Genetics in Medicine, 17, 460-466, (2015). Refinement of the critical 2p25.3 deletion region: the role of MYT1L in intellectual disability and obesity www.ncbi.nlm.nih.gov/pubmed/25232846
  • Mayo S. et al. Genetics in Medicine, 17, 683-684, (2015). Haploinsufficiency of the MYT1L gene causes intellectual disability frequently associated with behavioral disorder www.ncbi.nlm.nih.gov/pubmed/26240977
  • Blanchet P. et al. PLoS Genetics, 13, e1006957, (2017). MYT1L mutations cause intellectual disability and variable obesity by dysregulating gene expression and development of the neuroendocrine hypothalamus
    www.ncbi.nlm.nih.gov/pubmed/28859103
  • Coursimault, J., Guerrot, A. M., Morrow, M. M., Schramm, C., Zamora, F. M., Shanmugham, A., Liu, S., Zou, F., Bilan, F., … & Lecoquierre, F. (2022). MYT1L-associated neurodevelopmental disorder: Description of 40 new cases and literature review of clinical and molecular aspects. Human Genetics, 141(1), 65-80. https://pubmed.ncbi.nlm.nih.gov/34748075/

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