Conjoined twins and conjoined triplets: At the heart of the matter

Abstract

Conjoined triplets are among the rarest of human malformations, as are asymmetric or parasitic conjoined twins. Based on a very modest corpus of recent literature, we applied the embryonic disk model of conjoined twinning to 10 previously reported cases involving asymmetric anatomical multiplications to determine whether they concerned conjoined twins or conjoined triplets. In spite of their phenotypic similarities, we diagnosed four of these cases as conjoined twins and three of them as conjoined triplets. In the remaining three cases, no definite diagnosis could be made, as essential information was lacking from the reports. We conclude that it is not necessarily the expected duplication or triplication of structures that points to the correct diagnosis in these cases, but the number and mutual position of the hearts they presented with. Considering their rarity we stress to thoroughly investigate and describe internal (dys)morphology in novel cases of (asymmetric) conjoined twins and triplets to further unravel their pathogenicity and come to the correct diagnoses.

The role of the University of Padua medical school in the study of conjoined twins between 18th and early 19th century

“…The condition of this specimen is to be interpreted as laterally conjoined twins (parapagus diprosopus), forming a ventral conjunction with a third parasitic individual, which makes this a truly unique case of asymmetric conjoined triplets (Oostra et al, 2022 ).…”

“…The brain, instead, did not present anything abnormal. This condition was diagnosed as asymmetric prosopothoracoileopagus conjoined twins (Oostra et al, 2022 ), complicated by an omphalocele and what seemed to have been rectovesical fistulas.…”

Epigastric heteropagus conjoined twins combined with TRAP sequence

“…Epigastric heteropagus is a rare condition that refers to unequal and asymmetric conjoined twins in which the parasite is smaller and usually attached to the epigastrium of the autosite. 1 Twin reversed arterial perfusion (TRAP) sequence refers to a rare complication unique to monochorionic twin pregnancies in which a twin with an absent or rudimentary heart ('acardiac twin') is perfused by its co-twin ('pump twin') via aberrant arterioarterial anastomoses. 2 Here, we report an extremely rare case of epigastric heteropagus combined with TRAP sequence.…”

Craniorachipagus symmetric conjoined twinning: Identification of a fourth case and delineation of the phenotype

“…However, part of the reason why the scientific community reacts reluctantly on reports like the ones reviewed here is that their authors have a tendency to portray these exceedingly rare conditions as medical curiosities, stripping them from their scientific value by omitting essential clinical data. This not only concerns rachipagus (Kompanje, 2006) but also occurs with other unique conditions, such as conjoined triplets (Oostra et al, 2022). Since case reports are presently the only clue in expanding our knowledge regarding human conjoined twinning in general and (cranio)rachipagus in particular, it is entirely up to their authors to take their scientific responsibility and to be meticulous in their investigations, exhaustive in their data provision, detailed in their descriptions, and accurate in their terminology.…”