“…However, in three families, the two affected siblings were discordant with respect to the presence of a TEF (one sibling had EA only, the other EA and TEF), despite the fact that in one of the families the children had a mother with EA/TEF (Dennis et al, 1973;Pletcher et al, 1991;McMullen et al, 1996). Similarly, for affected twins, most sets of twins are concordant and only one report describes twins with a difference in EA/TEF subtypes (EA only and EA/TEF) (Woolley et al, 1961;Blank et al, 1967;King et al, 1977;Ohkuma, 1978;Whalen et al, 1987;McMullen et al, 1996;Ishimaru et al, 1998;Orford et al, 2000;Farquhar et al, 2002;Trobs et al, 2006). The fact that different types of EA/ TEF can occur within one family suggests (at least partly) overlapping etiologies.…”