Male parapagus dicephalus tripus tribrachius conjoined twin, discordant for anencephaly (1)

Lateral overview showing oblique positioning of the heads. The gluteal cleft of the left twin (black arrowhead) and the three lower extremities (black arrow) are distinguishable. Parapagus twins are conjoined twins that lie side by side with ventrolateral fusion. Parapagus dicephalus is a rare form of partial twinning with two heads side by side on one torso. Infants conjoined this way are sometimes called "two-headed babies" in popular media. If carried to term, most dicephalic twins are stillborn or die soon after birth (regardless of whether one is anencephalic, as in this case). (Source: Bovendeert JF, Nievelstein RA, Bleys RL, Cleypool CG. A parapagus dicephalus tripus tribrachius conjoined twin with a unique morphological pattern: a case report. J Med Case Rep 2020;14[1]:176. Creative Commons Attribution 4.0 International License, http://creativecommons.org/licenses/by/4.0.)