Tetralogy of Fallot in monozygotic twins

The causative mechanisms of congenital heart defects remain unclear and lit tle is known about the respective implication of chance, genetics and envir onment, though recent findings in molecular biology may provide further ins ight into understanding the pathophysiologic basis of congenital heart dise ases. Case report. - We report the exceptional but significant case of monozygoti c twins both affected by tetralogy of Fallot, for whom prenatal diagnosis r uled out 22q11 microdeletion. Conclusion. - We discuss how far this observation is consistent with the la test hypothesis, which emphasizes the leading role of genetic factors. Seve ral genes indeed, either separately or in combination, could be responsible for those defects, even if other influences may still come into play. (C) 2001 Editions scientifiques et medicales Elsevier SAS. .