ANENCEPHALY, DORSAL HYPERMELIA, AND DUPLICATION OF THE VERTEBRAL COLUMN - A RARE TYPE OF RACHIPAGUS CONJOINED TWINS

The rare combination of hypermelia with craniorachischisis and duplica tion of the vertebral column has been found in three cases, two publis hed and one previously unreported. Even though the previous authors ha d come to other conclusions, careful analysis of the details in these twins leads to the inescapable conclusion that they were all dorsally united parasitic rachipagus twins. The nature of the original union wa s clearly indicated by (1) the articulation of autositic ribs to two d ifferent vertebral columns but to a single ventral sternum, (2) the ar ticulation of parasitic ribs also to the two vertebral columns but fus ion of the ribs and clavicles dorsally without an interposed sternum, and (3) the dorsal location of the rudimentary viscera of the parasite . The orientation of notomelic arms was confirmatory but not diagnosti c. The proposed embryologic origin of these twins is presented. (C) 19 96 Wiley-Liss, Inc.