Conjoined twins

"Siamese twins" redirects here. For other uses, see Siamese twins (disambiguation).
Conjoined twins

X-ray of conjoined twins, cephalothoracopagus.
Classification and external resources
Specialty medical genetics
ICD-10 O33.7, Q89.4
ICD-9-CM 678.1, 759.4
DiseasesDB 34474
eMedicine ped/2936
MeSH D014428

Conjoined twins are identical twins[1] joined in utero. An extremely rare phenomenon, the occurrence is estimated to range from 1 in 49,000 births to 1 in 189,000 births, with a somewhat higher incidence in Southeast Asia and Africa.[2] Approximately half are stillborn, and an additional one-third die within 24 hours. Most live births are female, with a ratio of 3:1. Most stillborns are male.[2][3]

Two contradicting theories exist to explain the origins of conjoined twins. The more generally accepted theory is fission, in which the fertilized egg splits partially.[4] The other theory, no longer believed to be the basis of conjoined twinning,[4] is fusion, in which a fertilized egg completely separates, but stem cells (which search for similar cells) find like-stem cells on the other twin and fuse the twins together. Conjoined twins share a single common chorion, placenta, and amniotic sac, although these characteristics are not exclusive to conjoined twins as there are some monozygotic but non-conjoined twins who also share these structures in utero.[5]

The most famous pair of conjoined twins was Chang and Eng Bunker (Thai: อิน-จัน, In-Chan) (18111874), Thai brothers born in Siam, now Thailand. They traveled with P.T. Barnum's circus for many years and were labeled as the Siamese Twins. Chang and Eng were joined by a band of flesh, cartilage, and their fused livers at the torso. In modern times, they could have been easily separated.[6] Due to the brothers' fame and the rarity of the condition, the term "Siamese twins" came to be used as a synonym for conjoined twins.[7]

Types of conjoined twins

Conjoined twins are typically classified by the point at which their bodies are joined. The most common types of conjoined twins are:

Other less-common types of conjoined twins include:


Surgery to separate conjoined twins may range from very easy to very hard, depending on the point of attachment and the internal parts that are shared. Most cases of separation are extremely risky and life-threatening. In many cases, the surgery results in the death of one or both of the twins, particularly if they are joined at the head or share a vital organ. This makes the ethics of surgical separation, where the twins can survive if not separated, contentious. Alice Dreger of Northwestern University found the quality of life of twins who remain conjoined to be higher than is commonly supposed.[11] Lori and George Schappell and Abby and Brittany Hensel are notable examples.

In 1955, neurosurgeon Harold Voris (1902-1980)[12] and his team at Mercy Hospital in Chicago performed the first successful operation to separate Siamese twins conjoined (Craniopagus twins) at the head, which resulted in long-term survival for both.[13][14][15] The larger girl was reported in 1963 as developing normally, but the smaller was permanently impaired.[16]

In 1957, Bertram Katz and his surgical team made international medical history performing the world's first successful separation of conjoined twins sharing a vital organ.[17] Omphalopagus twins John Nelson and James Edward Freeman (Johnny and Jimmy) were born to Mr. and Mrs. William Freeman of Youngstown, Ohio, on April 27, 1956. The boys shared a liver but had separate hearts and were successfully separated at North Side Hospital in Youngstown, Ohio by Bertram Katz. The operation was funded by the Ohio Crippled Children's Service Society.[18]

Recent successful separations of conjoined twins include that of the separation of Ganga & Jamuna Shreshta in 2001, who were born in Kathmandu, Nepal, in 2000. The 197-hour surgery on the pair of craniopagus twins was a landmark one which took place in Singapore; the team was led by neurosurgeons Chumpon Chan and Keith Goh.[19] The surgery left Ganga with brain damage and Jamuna unable to walk. Seven years later, Ganga Shrestha died at the Model Hospital in Kathmandu in July 2009, at the age of 8, three days after being admitted for treatment of a severe chest infection.[20]

A case of particular interest was that of infants Rose and Grace ("Mary" and "Jodie") Attard, conjoined twins from Malta who were separated in Great Britain by court order Re A (Children) (Conjoined Twins: Surgical Separation) over the religious objections of their parents, Michaelangelo and Rina Attard. The surgery took place in November, 2000, at St Mary's Hospital in Manchester. The operation was controversial because Rose, the weaker twin, would die as a result of the procedure as her heart and lungs were dependent upon Grace's. (The twins were attached at the lower abdomen and spine.) However, if the operation had not taken place, it was certain that both twins would die.[21][22] Grace survived to enjoy a normal childhood.[23]

In 2003 two 29-year-old women from Iran, Ladan and Laleh Bijani, who were joined at the head but had separate brains (craniopagus) were surgically separated in Singapore, despite surgeons' warnings that the operation could be fatal to one or both. Their complex case was accepted only because high tech graphical imagery and modelling would allow the medical team to plan the risky surgery. Unfortunately, an undetected major vein hidden from the scans was discovered during the operation.[24] The separation was completed but both women died while still in surgery on July 8, 2003.


Embryo splitting in which zygote divide asexually, to produce identical children, is blocked by mitosis inhibitor.

Conjoined twins in history

Conjoined brothers from Nuremberg Chronicle (1493).
Conjoined twin sisters from Nuremberg Chronicle (1493).
Moche ceramics depicting conjoined twins. 300 CE Larco Museum Collection Lima, Peru.

The Moche culture of ancient Peru depicted conjoined twins in their ceramics dating back to 300 CE.[25] Writing around 415 CE, St. Augustine of Hippo in his book City of God refers to a man "double in his upper, but single in his lower half--having two heads, two chests, four hands, but one body and two feet like an ordinary man."[26] The earliest known documented case of conjoined twins dates from the year 942, when a pair of conjoined twin brothers from Armenia were brought to Constantinople for medical evaluation.

In Arabia, the twin brothers Hashim ibn Abd Manaf and 'Abd Shams were born with Hashim's leg attached to his twin brother's head. Legend says that their father, Abd Manaf ibn Qusai, separated his conjoined sons with a sword and that some priests believed that the blood that had flowed between them signified wars between their progeny (confrontations did occur between Banu al'Abbas and Banu Ummaya ibn 'Abd Shams in the year 750 AH).[27] The Muslim polymath Abū al-Rayhān al-Bīrūnī described Siamese twins in his book Kitab-al-Saidana.[28]

The English twin sisters Mary and Eliza Chulkhurst, who were conjoined at the back (pygopagus), lived from 1100 to 1134 (or 1500 to 1534) and were perhaps the best-known early historical example of conjoined twins. Other early conjoined twins to attain notice were the "Scottish brothers", allegedly of the dicephalus type, essentially two heads sharing the same body (14601488, although the dates vary); the pygopagus Helen and Judith of Szőny, Hungary (17011723), who enjoyed a brief career in music before being sent to live in a convent; and Rita and Cristina of Parodi of Sardinia, born in 1829. Rita and Cristina were dicephalus tetrabrachius (one body with four arms) twins and although they died at only eight months of age, they gained much attention as a curiosity when their parents exhibited them in Paris.

Grave of Eng and Chang Bunker near Mt. Airy, North Carolina

Several sets of conjoined twins lived during the nineteenth century and made careers for themselves in the performing arts, though none achieved quite the same level of fame and fortune as Chang and Eng. Most notably, Millie and Christine McCoy (or McKoy), pygopagus twins, were born into slavery in North Carolina in 1851. They were sold to a showman, J.P. Smith, at birth, but were soon kidnapped by a rival showman. The kidnapper fled to England but was thwarted because England had already banned slavery. Smith traveled to England to collect the girls and brought with him their mother, Monimia, from whom they had been separated. He and his wife provided the twins with an education and taught them to speak five languages, play music, and sing. For the rest of the century the twins enjoyed a successful career as "The Two-Headed Nightingale" and appeared with the Barnum Circus. In 1912 they died of tuberculosis, 17 hours apart.

Giovanni and Giacomo Tocci, from Locana, Italy, were immortalized in Mark Twain's short story "Those Extraordinary Twins" as fictitious twins Angelo and Luigi. The Toccis, born in 1877, were dicephalus tetrabrachius twins, having one body with two legs, two heads, and four arms. From birth they were forced by their parents to perform and never learned to walk, as each twin controlled one leg (in modern times physical therapy allows twins like the Toccis to learn to walk on their own). They are said to have disliked show business. In 1886, after touring the United States, the twins returned to Europe with their family, where they fell very ill. They are believed to have died around this time, though some sources claim they survived until 1940, living in seclusion in Italy.

List of notable conjoined twins

Names listed in boldface are of twins who have been separated.

Born 19th century and earlier

Chang and Eng Bunker, watercolor on ivory, 1835 or 1836

Born 20th century

Born 21st century

Conjoined twin lambs

In fiction

See also


  1. "Conjoined Twins Facts". University of Maryland Medical Center. Retrieved 6 Jan 2012.
  2. 1 2 "Clinics - Importance of angiographic study in preoperative planning of conjoined twins: case report". 1990-01-06. Retrieved 2014-08-03.
  3. "Conjoined Twins". Medscape. Retrieved 22 Oct 2015. (this article includes post-mortem images)
  4. 1 2 3 4 5 6 7 "The embryology of conjoined twins (Aug. 2004)". Child's Nervous System. 20 (8-9): 508–525. Aug 2004. doi:10.1007/s00381-004-0985-4. PMID 15278382.
  5. Le, Tao; Bhushan, Vikas; Vasan, Neil (2010). First Aid for the USMLE Step 1: 2010 20th Anniversary Edition. USA: The McGraw-Hill Companies, Inc. p. 121. ISBN 978-0-07-163340-6.
  6. "h2g2 - Twins - A369434". Retrieved 2014-08-03.
  7. "Conjoined Twins". University of Maryland Medical Center. January 8, 2010. Retrieved February 9, 2010.
  8. 1 2 3 4 5 6 7 8 9 10 11 12 Archived August 19, 2009, at the Wayback Machine.
  9. "". Retrieved 2014-08-03.
  10. Spencer, R (1995). "Rachipagus conjoined twins: They really do occur!". Teratology. 52 (6): 346–56. doi:10.1002/tera.1420520605. PMID 8711621.
  11. "One of Us: Conjoined Twins and the Future of Normal: Alice Domurat Dreger: 9780674018259: Books". Retrieved 2014-08-03.
  13. "The craniopagus malformation: classification and implications for surgical separation". Oxford University Press. April 5, 2006. Retrieved October 14, 2015.
  14. "Mercy Firsts". Retrieved October 14, 2015.
  15. "Seaparate Siamese Twins!". Chicago Tribune. April 22, 1955. Retrieved October 14, 2015.
  16. Voris, Harold C. (February 1963). "Cranioplasty in a Craniopagus Twin". Journal of Neurosurgery. 20 (2): 145–147. doi:10.3171/jns.1963.20.2.0145.
  17. "Dr. Bewrtram Katz, 83 - Obituary". Retrieved 2014-08-03.
  18. Retrieved April 11, 2013. Missing or empty |title= (help)
  19. "In Conversation with Medicine's Miracle Workers -- Dr Chumpon Chan and Dr Keith Goh". Channel News Asia Singapore. April 19, 2001. Archived from the original on January 14, 2011. Retrieved March 27, 2010.
  20. Archived November 5, 2013, at the Wayback Machine.
  21. "Siamese twin Jodie 'to go home soon'". BBC News. April 23, 2001. Retrieved March 27, 2010.
  22. Appel, Jacob M. Ethics: English high court orders separation of conjoined twins. Journal of Law Medicine & Ethics. 2000 Fall;28(3):312-3.
  23. "We don't know how to tell Gracie her sister died so she could live; EXCLUSIVE DILEMMA FACING TWINS' PARENTS DAILY Mirror BEST FOR REAL LIFE. - Free Online Library". Retrieved 2014-08-03.
  24. "Wired 11.10: Till Death Do Us Part". 2001-04-11. Retrieved 2014-08-03.
  25. Berrin, Katherine & Larco Museum. The Spirit of Ancient Peru:Treasures from the Museo Arqueológico Rafael Larco Herrera. New York: Thames and Hudson, 1997.
  26. "CHURCH FATHERS: City of God, Book XVI (St. Augustine)". Retrieved 2014-08-03.
  27. The Life of the Prophet Muhammad: Al-Sira Al-Nabawiyya By Ibn Kathir, Trevor Le Gassick, Muneer Fareed, pg. 132
  28. A. Zahoor (1997), Abu Raihan Muhammad al-Biruni, Hasanuddin U
  29. Bondeson, Jan (April 1992), "The Biddenden Maids: a curious chapter in the history of conjoined twins", Journal of the Royal Society of Medicine, London: Royal Society of Medicine Press, 85 (4): 217–221, PMC 1294728Freely accessible, PMID 1433064
  30. DA Staffenberg and JT Goodrich. Separation of craniopagus conjoined twins: an evolution in thought. Clin Plast Surg. 2005 Jan;32(1):25-34.
  31. "Herrintwins". Herrintwins. Retrieved 2014-08-03.
  32. "Many-limbed India girl in surgery". BBC News. 2007-11-06.
  33. "NOVA | Separating Twins". Retrieved 2014-08-03.

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