TBX5 and atrial septal defect: Here we report for the first time on a baby with CDG-1a with ASD, who has no family history of CHD or mutations in genes essential to cardiac septation such as NKX2-5, GATA4, and TBX5. This patient is followed up to 3-years old and a comparison of the changes in defect size and blood shunt of ASD has been made.