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Molecular characteristics

Asadollahi-Rauch syndrome (MED13L haploinsufficiency syndrome or MED13L-related intellectual disability) is caused by newly occurring (de novo) changes in MED13L gene, which mainly lead to the reduction of the amount of MED13L protein. Decreased amount of MED13L protein can disturb brain development and function, as well as formation of craniofacial and heart structures. Therefore, affected individuals present with intellectual disability, facial characteristics, and sometimes heart defects.

For detection of disease-causing changes in MED13L gene, genetic testing should be performed which involves the collection of a sample of blood or saliva from the affected individual and his/her parents. Analysing the DNA extracted from the patient’s sample and comparing it with the DNA of parents’ samples may lead to the detection of a disease-causing change in the MED13L gene that is not present in the healthy parents, i.e. a newly occurring (de novo) change.

If the patient’s clinical signs raise the suspicion of the syndrome, DNA sequencing of the MED13L gene can be done as the first step. If the patient’s characteristics are not sufficient to raise the suspicion of the syndrome because of their overlap with the characteristics observed in other genetic disorders, DNA sequencing of multiple genes, including MED13L, will be performed using a multi-gene panel or exome sequencing. In some patients, a piece from the DNA of the MED13L gene is deleted (missing) or duplicated which are called copy number changes. Depending on the analytical setting, for detecting these changes, other tests such as chromosomal microarray analysis or MLPA might be necessary.