MED13L haploinsufficiencysyndrome is a genetic syndrome that causes intellectual disability, speech problems, and behavioral problems. People with the syndrome usually have distinctive facial features, such as eyes that slant upwards, a flat nasal bridge with a bulb-like tip, very small chin (micrognathia), large and lowset ears, and broad forehead. Most children with the syndrome have poor muscle tone (hypotonia) and may take longer to learn to sit and walk independently (delayed motor skills). Some babies with MED13L haploinsufficiency syndrome are born with heart defects, which may be mild or severe. Other features may include short stature, cleft palate, problems with coordination (ataxia), and recurrent seizures (epilepsy).

MED13L haploinsufficiency syndrome is caused by changes (pathogenic variants, also called mutations) in the MED13Lgene. Diagnosis may be suspected due to distinctive facial features, speech delay, and intellectual disability, but must be confirmed by genetic testing. There is no cure or specific treatment for MED13L haploinsufficiency syndrome. Treatment depends on the types and severity of the medical, developmental, and behavioral problems affecting the person with the syndrome and may include heart surgery and therapies such as speech, occupational, and behavioral therapy.

Some infants with MED13L haploinsufficiency syndrome are born with heart defects, because the heart did not form properly. In some cases, the heart defects are mild, such as a patent foramen ovale, but in other cases, the heart defects may be more severe, such as transposition of the great arteries.

Other features of MED13L haploinsufficiency syndrome may include being shorter than other family members and peers (short stature), cleft palate, problems with coordination (ataxia), and recurrent seizures (epilepsy). Some people with the syndrome have severe symptoms, while others may be more mildly affected.

MED13Lgene. This gene provides the body with instructions for making a protein that helps the brain and the heart develop correctly.

Like most genes, MED13L comes in a pair (two copies). When one copy of this gene has a pathogenic variant, only one copy is working in the body (haploinsufficiency). Haploinsufficiency of MED13L causes the brain and sometimes the heart to not develop normally. This causes the different features associated with MED13L haploinsufficiency syndrome.

de novo pathogenic variant (mutation).

There have been some documented cases in which a person with this syndrome does inherit it from one parent. This may happen if the parent also has MED13L haploinsufficiency syndrome, but it was never diagnosed because the clinical features are mild in the parent. In this case, each child of the parent with MED13L pathogenic variant would have a 50% chance to inherit the syndrome. However, the clinical features in the child may be mild like the parent’s or the features may be more severe. The syndrome can also be inherited when some of the cells in the parent’s body has the pathogenic variant in MED13L, but most do not. In this case, the parent would have no clinical features of the syndrome, but each future child would be at an increased risk to have the syndrome.

MED13L gene through genetic testing, since many other genetic syndromes can cause similar clinical features.