A conjoined twin joined dorsally along the vertebral column is known as a "parasitic rachipagus
," from the Greek words "rachi" (spine) and "pagus" (fixed), and is the rarest type (2).
In the history of world medical records going back more than a century, Dominique is one of maybe 30 cases of children born with a parasitic rachipagus
twin condition in which a twin stops developing during gestation but fails to separate from the other body, says Dr.
They are further classified into eight basic types relative to their site(s) of union or pagus (Greek for joined): Omphalopagus (umbilicus/abdomen), thoracopagus (thorax/upper abdomen), cephalopagus (maxillofacial), craniopagus (skull), ischiopagus (pelvis), rachipagus
(spine) and pygopagus (sacrum).
The dorsally conjoined twins fuse with the closing neural folds either in the head (craniopagus), the coccygeal region (pyopagus), or in between these regions (rachipagus
Conjoined twins are classified according to the most prominent site of conjunction: thorax (thoracopagus); abdomen (omphalopagus); sacrum (pygopagus); pelvis (ischiopagus); skull (cephalopagus), side by side (parapagus) and back (rachipagus
in 1680, rachipagus
twin girls joined at the spine were born to a peasant woman to the horror of the attendants.
Thorax (thoracopagus 30-40%), abdomen (omphalopagus 25-30%), pyopagus (10-20%), pelvis (ischiopagus 20%), face (cephalopagus), skull (craniopagus 2-16%), back (rachipagus