A parasitic twin represents a rare developmental anomaly in which an asymmetrical, nonviable conjoined twin is attached to the host body at the time of birth. Rachipagus is among the rarest of conjoined twin subtypes and typically features a parasitic twin mass attached at the spine. Herein, the authors review the literature and describe the case of a 9-month-old girl presenting with a rachipagus parasitic twin consisting of a fully developed set of lower extremities originating from the midline upper back. After a complete workup to delineate parasite and autosite anatomy, the parasitic twin mass was successfully excised by a multidisciplinary team of surgeons, and the resulting defect was closed in a single stage.
Keywords: congenital; conjoined twin; diplomyelia; heteropagus twin; parasitic twin; rachipagus twin.