Thoracolumbar rachipagus parasitic twins with multiple congenital anomalies: A rare case report with review of literature.

Heteropagus, also known as parasitic twining, is the asymmetric twinning of conjoined identical or monozygotic twins. One severely deficient twin (the parasite) relies on the other twin's heart (the autosite) to survive. The circumstance only arises when parts of the body of the developed and delivered twin are joined to the undeveloped or underdeveloped twin. Very few case reports of this uncommon congenital defect have been published in the literature. Here, we describe a case of this atypical entity in a neonate in which the rudimentary pelvis and thigh of the parasite were attached to the autosite of the twin.