“…Presumed environmental factors during pregnancy are fetal intoxication in maternal diabetes (Martinez‐Frias, ; Genevieve et al, ), and hypo‐perfusion during early embryonic development in twin gestations (Davies and Gimenez‐Scherer, ; Schulz et al, ). A genetic background is suggested by findings in murine knockout models (Chiang et al, ; Litingtung et al, ; Ramalho‐Santos et al, ); the existence of multiply affected families (van Staey et al, ; Pletcher et al, ; McMullen et al, ; El‐Nabulsi and Carachi, ); higher concordance rates among monozygotic compared with dizygotic twins (Davies and Gimenez‐Scherer, ); the presence in 6 to 10% of patients of chromosomal aberrations (Depaepe et al, ; Robert et al, ; Torfs et al, ; Shaw‐Smith, ; Genevieve et al, ); and the fact that EA/TEF is a feature of various genetic syndromes (Shaw‐Smith, ; Jong et al, ).…”