atrial septal defect 5 (Monarch Disease Ontology entry MONDO_0013011) is any atrial heart septal defect in which the cause of the disease is a mutation in the ACTC1 gene. Also known as: ACTC1 atrial heart septal defect, ASD5, atrial heart septal defect caused by mutation in ACTC1, atrial heart septal defect type 5, atrial septal defect type 5.