MED12-Related Syndrome
MED12-related syndrome is also called Hardikar syndrome, Lujan syndrome, X-linked Ohdo syndrome, FG syndrome type 1, Opitz-Kaveggia syndrome, and nonspecific intellectual disability. For this webpage, we will be using the name MED12-related syndrome to encompass the wide range of variants observed in the people identified.
What is MED12-related syndrome?
MED12-related syndrome happens when there are changes in the MED12 gene. These changes can keep the gene from working as it should.
Key Role
The MED12 gene plays an important role in the development of the brain.
Symptoms
Because the MED12 gene is important for many parts of the body, some people may have:
- Intellectual disability, mild to moderate
- Developmental delay
- Autism or features of autism
- Behavior issues, such as aggressive behavior or obsessive compulsive disorder
- Brain changes seen on magnetic resonance imaging (MRI)
- Heart development defects
- Hearing issues
- Feeding issues and intestinal development issues
What causes MED12-related syndrome?
MED12-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. Genes are arranged in structures in our cells called chromosomes. Chromosomes and genes usually come in pairs, with one copy from the mother’s egg, and one copy from the father’s sperm.
We each have 23 pairs of chromosomes. One pair, called the X and Y chromosomes, differs between biological males and biological females. Biological females have two copies of the X chromosome and all its genes, one inherited from their mother and one inherited from their father. Biological males have one copy of the X chromosome and all its genes, inherited from their mother, and one copy of the Y chromosome and its genes, inherited from their father.
In most cases, parents pass on exact copies of the gene to their child. But the process of making the sperm and egg is not perfect. A variant in the genetic code can lead to physical issues, developmental issues, or both.
The MED12 gene is located on the X chromosome, therefore variants in this gene can affect biological males and biological females in different ways. Biological males who have variants in this gene will likely have MED12-related syndrome.
Biological females who have variants in this gene may or may not have symptoms of MED12-related syndrome. Biological females who have one working copy of the gene and one non-working copy are considered to be ‘carriers’. Even if a biological female does not have signs or symptoms of the syndrome, they can pass it along to their children. MED12-related syndrome may result in an X-linked dominant condition or an X-linked recessive condition depending on the genetic variant. Below, we have included details for both types of X-linked conditions.
X-linked dominant conditions
MED12-related syndrome may result from a spontaneous variant in the MED12 gene in the sperm or egg during development. When a brand new genetic variant happens in the genetic code it is called a ‘de novo’ genetic variant. The child can be the first in the family to have the gene 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 MED12 plays a key role in development, de novo variants in this gene can have a meaningful effect. Many parents who have had their genes tested do not have the MED12 gene variant found in their child who has the syndrome.
X-Linked Dominant Genetic Syndrome
X-linked recessive conditions
MED12-related syndrome may be the result of an inherited variant in MED12. This means that MED12-related syndrome happens because the genetic variant was passed down from a biological female parent. Biological females that carry the MED12 variant usually do not have symptoms, but sometimes they might.
X-Linked Recessive Genetic Syndrome
Why does my child have a change in the MED12 gene?
No parent causes their child’s MED12-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.
What are the chances that other family members of future children will haveMED12-related 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 MED12-related syndrome depends on the genes of both biological parents.
- Biological females who have a variant in the MED12 gene and are pregnant with a daughter have a 50 percent chance of passing on the same genetic variant and a 50 percent chance of passing on the working copy of the gene.
- If they are pregnant with a son, the child has a 50 percent chance of inheriting the genetic variant and the syndrome.
For a symptom-free brother or sister of someone who has MED12-related syndrome, the sibling’s risk of having a child who has MED12-related syndrome depends on the sibling’s genes and their parents’ genes.
- If neither parent has the same genetic variant causing MED12-related syndrome, the symptom-free sibling has a nearly 0 percent chance of having a child who would inherit MED12-related syndrome.
- If the biological mother has the same genetic variant causing MED12-related syndrome, and the symptom-free daughter has the variant, the symptom-free daughter’s chance of having a son who has MED12-related syndrome is 50 percent.
For a person who has MED12-related syndrome, the risk of having a child who has the syndrome is about 50 percent.
How many people have MED12-related syndrome?
As of 2024, about 84 people in the world with MED12-related syndrome have been identified in the medical clinic.
Do people who have MED12-related syndrome look different?
People who have MED12-related syndrome may look different. Appearance can vary and can include some but not all of these features:
- Lower than average muscle tone
- Finger growth defects
- Lower than average height
- Larger than average head size
- Noticeable nose
- Cleft lip or palate
- Eyes that are not aligned
How is MED12-related syndrome treated?
Scientists and doctors have only just begun to study MED12-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 MED12-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: 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 MED12-related syndrome
Diagnoses of the different MED12 syndromes are completed through the various clinical findings. More details are provided below for the various known clinical syndromes.
The MED12 gene is located on the X chromosome, and for some of the syndromes, female carriers do not usually have medical features – it depends on the genetic variant. To date, not all genetic variants have a clear link to a resulting clinical diagnosis.
Hardikar syndrome
People with Hardikar syndrome often have cleft lip or palate, liver issues and liver disease, intestinal issues, retina degeneration, narrow aorta of the heart, swelling of the kidneys, a cyst in the duct attached to the liver, and intellectual abilities that are within normal range. Most people do not have developmental delay.
All people with Hardikar syndrome are females with a MED12 frameshift or nonsense variants.
Lujan syndrome
People with Lujan syndrome have a specific MED12 variant called p.Asn1007Ser. Most people with Lujan syndrome have mild to moderate intellectual disability and speech that is in a high nasal range. Males often have a long thin appearance in their height, fingers, and toes.
Female carriers of Lujan syndrome are not expected to have symptoms. Other variants that have been suggested to be linked to Lujan syndrome include: p.Arg1214Cys, p.Arg1295His, and p.Trp1557Arg.
X-linked Ohdo syndrome
People with x-linked Ohdo syndrome often have intellectual disability, narrow eye openings, droopy eyelids, a small jaw, dental findings, and a triangle-shaped face. Some people might have a smaller than average head size and shorter than average height. Many people with x-linked Ohdo syndrome might not develop the ability to speak, have hearing loss, have hyper mobile joints, and have hyperactivity.
Usually, males with x-linked Ohdo syndrome have a de novo, new variant, or inherited variant from an unaffected mother. Although, affected mothers have been found.
Medical features associated with the MED12 genetic variant are thought to more or less happen in a female due to a process called X inactivation. This is a random process where a cell chooses one X chromosome to silence gene expression. This means that if the X chromosome that has the MED12 genetic variant is being silenced or turned off, this person may be more likely to have medical features.
Variants that have been suggested to be associated with x-linked Ohdo syndrome include: p.Glu172Gln, p.Arg296Glu, and p.Arg1148His. But, some of these variants have been associated with other MED12-related syndromes.
FG syndrome type 1 or Opitz-Kaveggia syndrome
FG syndrome type 1 is also known as Opitz-Kaveggia syndrome. People with FG syndrome type 1 often have neurodevelopmental delays; facial features that include larger than average head size and wide-spaced eyes; broad thumbs; organ formation issues, such as intestinal, heart, or skeletal issues; and eager to please behavior. In addition, people with FG syndrome type 1 are usually larger than average, have a larger than average head size, and have borderline to average or above average intelligence.
Female carriers are not expected to have symptoms. Common variants associated with FG syndrome type 1 include: p.Gly958Glu, and p.Arg961Trp.
Nonspecific intellectual disability
The medical features of nonspecific intellectual disability caused by a MED12 genetic variant are not consistent with one of the above MED12-related syndromes. Feeding issues are relatively common, as well as bone and development defects. Facial features in people diagnosed with nonspecific intellectual disability overlap with the other MED12-related syndromes. Defects in head size are not common in females.
Males and female carriers with damaging MED12 variants have been diagnosed with nonspecific intellectual disability. A range of variants are possible and these include missense variants and frameshift or nonsense variants have been diagnosed in people with nonspecific intellectual disability.
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 MED12: www.simonssearchlight.org/research/what-we-study/med12
- Simons Searchlight Facebook group: https://www.facebook.com/groups/303782692692130
Sources and References
The content in this guide comes from published studies about MED12-related syndrome. Below you can find details about each study, as well as links to summaries or, in some cases, the full article.
- Lyons MJ. MED12-Related Disorders. In: Adam MP, Feldman J, Mirzaa GM, et al., eds. GeneReviews®. Seattle (WA): University of Washington, Seattle; June 23, 2008.
- Maia N, Ibarluzea N, Misra-Isrie M, et al. Missense MED12 variants in 22 males with intellectual disability: From nonspecific symptoms to complete syndromes. Am J Med Genet A. 2023;191(1):135-143. doi:10.1002/ajmg.a.63004