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Updated: May 10, 2026
Transuterine Fetal Tracheal Occlusion Model in Mice
Published on: February 5, 2021
Case of cephalothoracopagus conjoined twinning in an embryonic mouse
Thomas E Hynd1, Cadie L Buckley, Scott Lozanoff
1Department of Anatomy, Biochemistry and Physiology, John A. Burns School of Medicine, University of Hawaii, Honolulu, HI 96813, USA. hynd@hawaii.edu
Background:
Cephalothoracopagus twinning is extremely rare, and it is characterized by fusion of the head and thorax, two separate spines, pelves, and fore- and hindlimbs.
Case:
In this case study, we describe cephalothoracopagus twinning in an embryonic mouse displaying a large but exencephalic head, median facial cleft, a single eye, and a second hindbrain rotated roughly 90° from a second spinal cord. There is a bony connection joining the clavicles, resulting in merged asternal thoracic cavities containing two hearts and four lungs. The abdominal cavities contain double caudal digestive tract structures, but a single esophagus and stomach.
Conclusion:
There are several proposed theories regarding the mechanism of spontaneous conjoined twinning; however, the specific mechanisms are still largely unknown. In this report, we highlight the morphological features in a murine example of cephalothoracopagus twinning, furthering our understanding of this rare occurrence while also demonstrating developmental morphogenesis consistent with that reported for human conjoined twins.
