Atrial Septal Defect 4
OMIM number: 611363
Comments closing date: 08/09/2026
Atrial septal defect 4 is a hereditary (genetic) predisposition to congenital cardiac defects. It is
caused by a mutation in a gene called TBX20. When the TBX20 gene is working, it is involved in
the formation of the heart during pregnancy. If a person is born with a mutation (also called
“pathogenic variant”) in this gene, it is associated with a wide spectrum of problems with the
structure of the heart. These problems can be very severe and life-limiting, or more manageable. It is thought that nearly everyone with a pathogenic variant in this gene will have changes to the heart, but again the severity is extremely variable and difficult to predict. Heart problems might be
addressed surgically in childhood or adulthood. Heart problems linked to this gene include defects
in the walls separating the heart (septation), the growth of the chambers of the heart, and/or the
valves, or disease of the heart muscle. Depending on the severity of the heart defects, the condition
can be life-limiting. It shows autosomal dominant inheritance, meaning each conception has a 1 in 2
chance of being affected.
