Types of Conjoined Twins

1. Inferior conjunction:

 

* Diprosopus (<1%)
* Dicephalus (<1%)
* Ischiopagus (6%)
* Pygopagus (18%)

Two faces + one head + one body
Two heads + two necks + one body
Joined by inferior sacrum + coccyx (spinal columns are separate but lie in the same axis)
Joined by posterolateral sacrum + coccyx.

2. Superior conjunction:

 

* Dipygus         (<1%)
* Syncephalus  (<1%)
* Craniopagus (2%)

One head, thorax, abdomen + two pelvises + four legs
Facial fusion (faces turned laterally)
± thoracic fusion
Joined between homologous portions of cranial vault.

 

 

* Cephalothorachopagus janiceps – fused head (with two faces looking in opposite directions) and thorax. Subtype disymmetros when faces are identical, and monosymmetros when the faces are dissimilar. Named after the Roman god, Janus.

 

  3. Middle Conjunction:

* Thoracopagus (40%) - Joined between thoracic walls; cojoined hearts (75%)

 


 


* Omphalopagus (34%) - Joined between umbilicus + xiphoid.

 


* Xiphopagus  (<1%) - Joined at xiphoid.
 -

* Thoracoomphalopagus - Joined at any level of the spinal column above the sacrum.

               (28%)

* Rachipagus       (<1%)

 

4. Incomplete Duplication

Duplication of one part of the body. Incomplete parasitic twinning with the parasite attached to the host’s epigastrium is extremely rare (2,3). Epigastric heteropagus refers to unequal and asymmetric conjoined twins in which the dependent parasite is smaller and attached to the epigastrium of the dominant component (autosite).

There is male preponderance and no major connection of vessels, bowel or bones. The etiology of such a malformation is still controversial.

 

 

 

 

REFERENCES
  1. Baldwin VJ. Pathology of multiple pregnancy. In: Wigglesworth JS, Singer DB (eds). Textbook of fetal and perinatal pathology. Boston, Mass: Blackwell, 1991:306-343.
  2. Hwang EH, Han SJ, Lee JS et. Al. An unusual case of monozygotic epigastric twinning. J Pediatr Surg 1996;31:1457-1460.
  3. Chadha R, Bagga D, Dhar A et.al. Epigastric heteropagus. J Pediatr Surg 1993;28:723-727.