The term 'atrioventricular septal defect' (AVSD) covers a spectrum of congenital heart malformations characterized by a common atrioventricular junction coexisting with deficient atrioventricular septation. In ostium primum atrial septal defect (ASD) there are separate atrioventricular valvar orifices despite a common junction, whereas in complete AVSD the valve itself is also shared (summary by Craig, 2006).
AVSD, also designated endocardial cushion defect or atrioventricular canal defect (AVCD), is known to occur in either a nonsyndromic (isolated) form or, more commonly, as part of a malformation syndrome. The 2 syndromes most frequently associated with AVSD are Down syndrome (190685), in which AVSD is the most frequent congenital heart defect, and Ivemark syndrome (208530) (summary by Carmi et al., 1992).
Genetic Heterogeneity of Isolated Atrioventricular Septal Defect
An AVSD susceptibility locus (AVSD1) maps to chromosome 1p31-p21; AVSD2 (606217) is caused by mutation in the CRELD1 gene (607170) on chromosome 3p25; AVSD4 (614430) is caused by mutation in the GATA4 gene (600576) on chromosome 8p23.1; and AVSD5 (614474) is caused by mutation in the GATA6 gene (601656) on chromosome 18q11.
A form of AVSD, designated AVSD3, was thought to be caused by mutation in the GJA1 gene (121014.0011), but this variant has been reclassified as a variant of unknown significance.
Somatic mutations in the HAND1 gene (602406) have been identified in tissue samples from patients with AVSDs. [from
OMIM]