FAMILIAL ATRIOVENTRICULAR SEPTAL-DEFECT - POSSIBLE GENETIC MECHANISMS

Background-Most non chromosomal congenital heart defects are thought t o be caused by the interaction of genetic factors involving multiple g enes and environmental factors. Families that have several affected me mbers have been reported, however, which suggests that a single autoso mal dominant or recessive gene may cause the cardiac defects. A family in which atrioventricular septal defect seemed to be a single gene di sorder is reported. Observations-A family in which the mother and her two daughters from different fathers had atrioventricular septal defec t not associated with trisomy 21 is reported. Conclusions-This family raises the possibility that cytoplasmic or mitochondrial inheritance m ay be involved in the causation of atrioventricular septal defects. Th e available data from pedigrees from other cases of familial atriovent ricular septal defect do not support this genetic mechanism, but sugge st that there is a subgroup without trisomy 21 that has a single gene disorder.