atrioventricular septal defect 3
An autosomal dominant heart malformation (OMIM:600309) characterised by a common atrioventricular junction coexisting with deficient atrioventricular septation. The complete form entails underdevelopment of the lower part of the atrial septum and the upper part of the ventricular septum; the valve itself is also shared. A less severe form—ostium primum atrial septal defect—is characterised by separate atrioventricular valvar orifices despite a common junction
Molecular pathology Defects of GJA1, which encodes a gap junction protein (connexin) thought to play a key role in the synchronised contraction of the heart and in embryonic development, cause atrioventricular septal defect 3.