Parasitic fetus is a kind of conjoined twin, in which one of the twins is resorbed and some parts of the body can remain attached to the other twin. In the spinal form of parasitic twin-the so-called parasitic rachipagus-an ectopic or accessory limb is attached to the back of a normal baby or only a mass of viable tissue may remain.

Navaei et al. report two cases of rachipagus that one had a lower extremity on her back and the other had some tissues similar to genitalia and formed bony structures on his back ¹⁾.