An unusual case of monozygotic epigastric heteropagus twinning.

Epigastric heteropagus refers to unequal and asymmetric conjoined twins in which the dependent component (parasite) is smaller and usually attached to the epigastrium of the dominant component (autosite). Epigastric heteropagus is a very rare type of conjoined twins. It is generally assumed that conjoined twins represent a form of monozygotic twinning, but there has been no confirmation of this monozygotic hypothesis. Epigastric heteropagus twins differ in several ways from symmetrical conjoined twins. These include male preponderance, and no major connection of vessels, bowels, or bones. These significant characteristics suggest to the authors that the fusion of two fertilized ova and the atrophy of one fetus resulted in this interesting malformation. However, a DNA study indicated monozygotic origin in their case. The possible pathogenesis was ischemic atrophy of the body structure of the monozygotic conjoined twins at an early gestational age.