[Tetralogy of Fallot in monozygotic twins].

Unlabelled: The causative mechanisms of congenital heart defects remain unclear and little is known about the respective implication of chance, genetics and environment, though recent findings in molecular biology may provide further insight into understanding the pathophysiologic basis of congenital heart diseases.

Case Report: We report the exceptional but significant case of monozygotic twins both affected by tetralogy of Fallot, for whom prenatal diagnosis ruled out 22q11 microdeletion.

Conclusion: We discuss how far this observation is consistent with the latest hypothesis, which emphasizes the leading role of genetic factors. Several genes indeed, either separately or in combination, could be responsible for those defects, even if other influences may still come into play.