Consistent with this model, a small study of non-syndromic AVSD found that among 34 persons who carried a mutation of one of six AVSD genes (NIPBL, CHD7, CEP152, BMPR1A, ZFPM2, MDM4), eight persons carried two or more mutations of the six genes [39]. This evidence concerns the gene BMPR1A and familial atrioventricular septal defect.