ITPR1 and Patent ductus arteriosus: However, there is one clinical feature which can aid the decision of whether to test ACTA2 in addition to ITPR1. In the largest series of ACTA2 p.Arg179 cases (33 individuals), the only feature reliably present at birth in all cases, other than the iris defect, was cardiac: a large patent ductus arteriosus (PDA, 91%) or aortopulmonary septal defect (9%).