ACTC1 and atrial septal defect: The co-occurrence of these congenital heart defects is notable because ACTC1 is well established to underlie isolated cardiac abnormalities, including dilated and hypertrophic cardiomyopathy (MIM: 613424, 612098), atrial septal defects (MIM: 612794), and left ventricular noncompaction (MIM: 613424).