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Conjoined twins

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

Conjoined twins
Other namesSiamese twins, monstra duplicia
X-ray of conjoined twins, Cephalothoracopagus.
SpecialtyMedical genetics Edit this on Wikidata
SymptomsBodies fused
ComplicationsDepends on type
Usual onsetBeginning of pregnancy
DurationLifelong
Typessee article
CausesIncomplete fission
TreatmentSurgery, symptomatic care
PrognosisDepends on type; occasionally may survive

Conjoined twins, popularly referred to as Siamese twins,[1][2] are twins joined in utero.[a] It is a very rare phenomenon, estimated to occur in anywhere between one in 50,000 births to one in 200,000 births, with a somewhat higher incidence in southwest Asia and Africa.[5] Approximately half are stillborn, and an additional one-third die within 24 hours. Most live births are female, with a ratio of 3:1.[5][6]

Two possible explanations of the cause of conjoined twins have been proposed. The one that is generally accepted is fission, in which the fertilized egg splits partially.[7] The other explanation, no longer believed to be accurate,[7] is fusion, in which the fertilized egg completely separates, but stem cells (that search for similar cells) find similar stem cells on the other twin and fuse the twins together. Conjoined twins share a single common chorion, placenta, and amniotic sac in utero, but so do some monozygotic but non-conjoined twins.[8]

Chang and Eng Bunker (1811–1874) were brothers born in Siam (now Thailand) who traveled widely for many years and were known internationally as the Siamese Twins. Chang and Eng were joined at the torso by a band of flesh and cartilage, and by their fused livers. In modern times, they could easily have been separated.[9] Due to the brothers' fame and the rarity of the condition, the term Siamese twins came to be associated with conjoined twins.

Causes

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There are two hypotheses about the development of conjoined twins.

  1. a single fertilized egg does not fully split during the process of forming identical twins. If the zygote division occurs after two weeks of the development of the embryonic disc, it results in the formation of conjoined twins.[10]
  2. fusion of two fertilized eggs occurs early in development.

Partial splitting of the primitive node and streak may result in the formation of conjoined twins. These twins are classified according to the nature and degree of their union. Occasionally, monozygotic twins are connected only by a common skin bridge or by a common liver bridge. The type of twins formed depends on when and to what extent abnormalities of the node and streak occurred. Misexpression of genes, such as goosecoid, may also result in conjoined twins.[11] Goosecoid activates inhibitors of BMP4 and contributes to regulation of head development. Over- or underexpression of this gene in laboratory animals results in severe malformations of the head region, including duplications, similar to some types of conjoined twins.[12]

Types

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

  • Thoracopagus (28% of cases):[7] Two bodies fused from the upper chest to the lower chest. These twins usually share a heart and may also share the liver or part of the digestive system.[13] Survival rate is poor.[14]
  • Thoraco-omphalopagus (18.5%):[7] Two bodies fused from the upper chest to lower belly. The heart is always shared in these cases.[13] As of 2015, twins who share a heart have not been able to both survive separation; a designated twin who is allotted the heart may survive if the other twin is sacrificed.
  • Omphalopagus (10%):[7] Two bodies fused at the lower abdomen. Unlike thoracopagus, the heart is not shared; however, the twins often share a liver, a digestive system, a diaphragm and other organs.[13] Survival rate is 82%.[14]
  • Parasitic twins (10%):[7] Twins that are asymmetrically conjoined, resulting in one twin that is small, less formed, and dependent on the larger twin's organs for survival.
  • Craniopagus (6%):[7] Fused skulls, but separate bodies. These twins' heads may be conjoined at the back, front, or side of the head, but not on the face or at the base of the skull.[13] Survival rate is poor.[14]

Other, less common types of conjoined twins include:

  • Cephalopagus: Two faces on opposite sides of a single, conjoined head; the upper portion of the body is fused while the bottom portions are separate. These twins generally cannot survive due to severe malformations of the brain. This is also known as janiceps (after the two-faced Roman deity Janus).[13]
  • Syncephalus: One head with a single face but four ears and two bodies.[13]
  • Cephalothoracopagus: Bodies fused at the head and thorax, with two faces facing in opposite directions, or sometimes with a single face and an enlarged skull.[13][15]
  • Xiphopagus: Two bodies fused in the xiphoid cartilage, which extends approximately from the navel to the lower breastbone. These twins almost never share any vital organs, with the exception of the liver.[13] A famous example is Chang and Eng Bunker.
  • Ischiopagus: Fused lower half of the two bodies, with spines conjoined end-to-end at a 180° angle. These twins have four arms; one, two, three or four legs; and typically one set of external genitalia and one anus.[13] Survival rate is 63%.[14]
  • Omphalo-Ischiopagus: Fused in a similar fashion to ischiopagus twins, but facing each other, with a joined abdomen, akin to omphalopagus. These twins have four arms, and two, three, or four legs.[13]
  • Parapagus: Fused side by side with a shared pelvis. Those that are dithoracic parapagus are fused at the abdomen and pelvis, but not at the thorax. Those that are diprosopic parapagus have one trunk and two faces. Those that are dicephalic parapagus have one trunk and two heads, and may have two (dibrachius), three (tribrachius), or four (tetrabrachius) arms.[13] Survival rate is poor.[14]
  • Craniopagus parasiticus: Like craniopagus, but with a second bodiless head attached to the dominant head.
  • Pygopagus or Iliopagus: Two bodies joined at the pelvis.[13] Survival rate is 68%.[14]
  • Rachipagus: Twins joined along the back of their bodies, with fusion of the vertebral arches and the soft tissue from the head to the buttocks.[16] Twins of this type cannot be separated.[14]
  • Tricephalus (conjoined triplets): Extremely rare conjoining of 3 fetuses. Very few confirmed cases, both human and animal, are known.[17]

Treatment

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Separation

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Surgery to separate conjoined twins may range from very easy to very difficult depending on the point of attachment and the internal parts that are shared.[18] Most cases of separation are extremely risky and life-threatening. Though there have been a number of successful separations throughout history, 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.[19] Lori and George Schappell and Abby and Brittany Hensel are notable examples.

The first recorded separation of conjoined twins took place in the Byzantine Empire in the 900s. One of the conjoined twins had already died, so the doctors of the town attempted to separate the dead twin from the surviving twin. The result was briefly successful, as the remaining twin lived for three days after separation. The next recorded case of separating conjoined twins was several centuries later, in Germany, in 1689.[20][21] The first recorded successful separation of conjoined twins was performed in 1689 by Johannes Fatio.[22] Around this same time Dr. Böhm of Gunzenhausen separated his own children, a pair of omphalopagus or xiphopagus twins; the feebler twin died four days later, but the healthier one was still alive and well at age five, when the case was reported.[23] In 1955, neurosurgeon Harold Voris (1902-1980)[24] and his team at Mercy Hospital in Chicago performed the first successful operation to separate craniopagus twins (conjoined at the head), which resulted in long-term survival for both.[25][26][27] The larger girl was reported in 1963 as developing normally, but the smaller girl was permanently impaired.[28]

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.[29] Omphalopagus twins John Nelson and James Edward Freeman (Johnny and Jimmy) were born in 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.[30]

Recent successful separations of conjoined twins include that of the separation of Ganga and Jamuna Shreshta in 2001, who were born in Kathmandu, Nepal, in 2000. The 97-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.[31] 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 eight, three days after being admitted for treatment of a severe chest infection.[32]

Infants Rose and Grace Attard, conjoined twins from Malta, were separated in the United Kingdom by court order Re A over the religious objections of their parents, Michaelangelo and Rina Attard. The twins were attached at the lower abdomen and spine. 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. However, if the operation had not taken place, it was certain that both twins would die.[33][34] Grace survived to enjoy a normal childhood.[35]

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 technologically advanced graphical imagery and modeling would allow the medical team to plan the risky surgery. However, an undetected major vein hidden from the scans was discovered during the operation.[36] The separation was completed but both women died while still in surgery.

In 2019 Safa and Marwa Ullah were separated at Great Ormond Street Hospital in London, England. The twins, born January 2017, were joined at the top of the head with separate brains and a cylindrical shared skull with the twins each facing in opposite directions to one another. The surgery was jointly led by neurosurgeon Owase Jeelani and plastic surgeon Professor David Dunaway. The surgery presented particular difficulties due to a number of shared veins and a distortion in the shape of the girls' brains, causing them to overlap. The distortion would need to be corrected in order for the separation to go ahead. The surgery utilized a team of more than 100 including bio engineers, 3D modelers and a virtual reality designer. The separation was completed in February 2019 following a total of 52 hours of surgery over three separate operations. As of July 2019, both girls remained healthy and the family planned to return to their home in Pakistan in 2020.[37][38]

History

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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.[39] Writing around 415 AD, 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."[40]

According to Theophanes the Confessor, a Byzantine historian of the 9th century, around 385/386 AD, he writes that "in the village of Emmaus in Palestine, a child was born perfectly normal below the navel but divided above it, so that it had two chests and two heads, each possessing the senses. One would eat and drink but the other did not eat; one would sleep but the other stayed awake. There were times when they played with each other, when both cried and hit each other. They lived for a little over two years. One died while the other lived for another four days and it, too, died."[41]

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).[42] The Muslim polymath Abū al-Rayhān al-Bīrūnī described conjoined twins in his book Kitab-al-Saidana.[43]

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 (1460–1488, although the dates vary); the pygopagus Helen and Judith of Szőny, Hungary (1701–1723), 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.

Giacomo and Giovanni 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. They are believed to have died around this time, though some sources claim they survived until 1940, living in seclusion in Italy.

Notable people

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Born 19th century and earlier

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

Born 20th century

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Born 21st century

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In fiction

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Conjoined twins have been the focus of several works of fiction, including:

See also

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Notes

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  1. ^ Conjoined twins are almost universally assumed to always be monozygotic, but dizygotic conjoined twins are theoretically possible.[3][4]

References

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  1. ^ "conjoined twin". Encyclopedia Britannica. Retrieved November 5, 2021.
  2. ^ "Medical Definition of Conjoined twin". MedicineNet. Retrieved November 5, 2021.
  3. ^ Maymon, Ron; Mendelovic, Sonia; Schachter, Morey; Ron-El, Raphael; Weinraub, Zwi; Herman, Arie (September 2005). "Diagnosis of conjoined twins before 16 weeks' gestation: The 4-year experience of one medical center". Prenatal Diagnosis. 25 (9): 839–843. doi:10.1002/pd.1274. PMID 16170850. S2CID 32204640.
  4. ^ Schiewe, Mitchel C.; Whitney, John B.; Anderson, Robert E. (February 1, 2015). "Potential risk of monochorionic dizygotic twin blastocyst formation associated with early laser zona dissection of group cultured embryos". Fertility and Sterility. 103 (2): 417–421. doi:10.1016/j.fertnstert.2014.11.009. PMID 25516079. one could predict dizygotic conjoined twins occurring less than 1 in every 4.7 billion ovulation cycles
  5. ^ a b Carnevale, Francisco Cesar; Borges, Marcus Vinicius; Affonso, Breno Boueri; Pinto, Ricardo Augusto de Paula; Tannuri, Uenis; Maksoud, João Gilberto (April 2006). "Importance of angiographic study in preoperative planning of conjoined twins: case report". Clinics. 61 (2): 167–70. doi:10.1590/S1807-59322006000200013. PMID 16680335.
  6. ^ Conjoined Twins at eMedicine
  7. ^ a b c d e f g Kaufman, M.H. (August 2004). "The embryology of conjoined twins". Child's Nervous System. 20 (8–9): 508–25. doi:10.1007/s00381-004-0985-4. PMID 15278382. S2CID 206964928.
  8. ^ Tao Le; 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.
  9. ^ "h2g2 – Twins – A369434". Bbc.co.uk. Retrieved August 3, 2014.
  10. ^ Konar, Hiralal (May 10, 2015). DC Dutta's textbook of obstetrics (Eighth ed.). JP Medical. p. 233. ISBN 9789351527237.
  11. ^ Sadler, Thomas W. (October 29, 2018). Langman's medical embryology (14th ed.). Wolters Kluwer. p. 124. ISBN 9781496383907.
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  16. ^ Spencer, Rowena (December 1995). "Rachipagus conjoined twins: They really do occur!". Teratology. 52 (6): 346–356. doi:10.1002/tera.1420520605. PMID 8711621.
  17. ^ Oostra, Roelof-Jan; Schepens-Franke, Annelieke N.; Magno, Giovanni; Zanatta, Alberto; Boer, Lucas L. (July 15, 2022). "Conjoined twins and conjoined triplets: At the heart of the matter". Birth Defects Research. 114 (12): 596–610. doi:10.1002/bdr2.2066. ISSN 2472-1727. PMC 9546242. PMID 35766259. S2CID 250114880.
  18. ^ Fallon, Sara C.; Olutoye, Oluyinka O. (October 1, 2018). "The surgical principles of conjoined twin separation". Seminars in Perinatology. Conjoined Twins. 42 (6): 386–392. doi:10.1053/j.semperi.2018.07.013. ISSN 0146-0005. PMID 30477661. S2CID 53767929.
  19. ^ Dreger, Alice Domurat (2004). One of Us: Conjoined Twins and the Future of Normal. Harvard University Press. ISBN 978-0-674-01825-9.
  20. ^ "The Case of Conjoined Twins in 10th Century Byzantium". Medievalists.net. January 4, 2014.
  21. ^ Montandon, Denys (2015). "The unspeakable history of Thoracopagus twins' separation" (PDF). ISAPS News. 9 (3): 47–48. Archived (PDF) from the original on February 25, 2017.
  22. ^ Kompanje, Erwin J. O. (December 1, 2004). "The First Successful Separation of Conjoined Twins in 1689: Some Additions and Corrections". Twin Research. 7 (6): 537–541. doi:10.1375/1369052042663760. PMID 15607002.
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  24. ^ "Voris, Harold C." The University of Chicago Photographic Archive. 1972. Retrieved July 30, 2017.
  25. ^ Stone, James L.; Goodrich, James T. (May 1, 2006). "The craniopagus malformation: classification and implications for surgical separation". Brain. 129 (5): 1084–1095. doi:10.1093/brain/awl065. PMID 16597654.
  26. ^ "Mercy Care Firsts". Mercy Hospital & Medical Center Chicago. Archived from the original on May 29, 2019. Retrieved October 14, 2015.
  27. ^ "Separate Siamese Twins!". Chicago Tribune. April 22, 1955. Retrieved October 14, 2015.
  28. ^ 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. PMID 14192083. S2CID 37985174.
  29. ^ "Dr. Bewrtram Katz, 83 – Obituary". Vindy.com. Archived from the original on November 10, 2013. Retrieved August 3, 2014.
  30. ^ [1][dead link‍]
  31. ^ "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.
  32. ^ "Nepali twin dies 7 years after 97-hour separation surgery". Monsters and Critics. July 30, 2008. Archived from the original on November 1, 2008.
  33. ^ "Siamese twin Jodie "to go home soon"". BBC News. April 23, 2001. Retrieved March 27, 2010.
  34. ^ Appel, Jacob M. (September 2000). "Ethics: English High Court Orders Separation of Conjoined Twins". The Journal of Law, Medicine & Ethics. 28 (3): 312–313. doi:10.1111/j.1748-720x.2000.tb00678.x. PMID 11210387. S2CID 36191724.
  35. ^ "We don't know how to tell Gracie her sister died so she could live". The Mirror. July 9, 2007. Retrieved August 3, 2014 – via Free Online Library.
  36. ^ "Wired 11.10: Till Death Do Us Part". Wired. April 11, 2001. Retrieved August 3, 2014.
  37. ^ "The battle to separate Safa and Marwa". BBC News. Retrieved July 18, 2019.
  38. ^ "Separating conjoined twins". www.gosh.nhs.uk. Archived from the original on July 17, 2019. Retrieved July 18, 2019.
  39. ^ Berrin, Katherine & Larco Museum. The Spirit of Ancient Peru:Treasures from the Museo Arqueológico Rafael Larco Herrera. New York: Thames and Hudson, 1997.
  40. ^ "CHURCH FATHERS: City of God, Book XVI (St. Augustine)". Newadvent.org. Retrieved August 3, 2014.
  41. ^ The Chronicle of Theophanes Confessor. Byzantine and Near Eastern History, AD 284–813. Translated with Introduction and Commentary by Cyril Mango and Roger Scott. Oxford: Clarendon Press, 1997, p. 106-107.
  42. ^ The Life of the Prophet Muhammad: Al-Sira Al-Nabawiyya By Ibn Kathir, Trevor Le Gassick, Muneer Fareed, pg. 132
  43. ^ A. Zahoor (1997), Abu Raihan Muhammad al-Biruni Archived February 25, 2020, at the Wayback Machine, Hasanuddin U
  44. ^ Bondeson, Jan (April 1992), "The Biddenden Maids: a curious chapter in the history of conjoined twins", Journal of the Royal Society of Medicine, 85 (4), London: Royal Society of Medicine Press: 217–221, doi:10.1177/014107689208500413, PMC 1294728, PMID 1433064
  45. ^ Miller, Sarah (2021). Violet and Daisy: The Story of Vaudeville's Famous Conjoined Twins. New York: Schwartz & Wade Books. p. 221. ISBN 978-0593119723.
  46. ^ "6 Oldest Living Conjoined Twins in the World". September 5, 2019. Retrieved June 21, 2022.
  47. ^ "First same-sex conjoined twins to identify as different genders". Guinness World Records. Retrieved March 11, 2023.
  48. ^ Two Heads, One Body: The Remarkable Story of Conjoined Twins Katie & Eilish | Our Life, retrieved December 3, 2022
  49. ^ Staffenberg, David A.; Goodrich, James T. (January 2005). "Separation of craniopagus conjoined twins: an evolution in thought". Clinics in Plastic Surgery. 32 (1): 25–34. doi:10.1016/j.cps.2004.09.002. PMID 15636762.
  50. ^ "Many-limbed India girl in surgery". BBC News. November 6, 2007.
  51. ^ "Herrin Twins". Archived from the original on June 6, 2014. Retrieved August 3, 2014.
  52. ^ "Separating Twins". NOVA. Pbs.org. February 8, 2012. Retrieved August 3, 2014.
  53. ^ Drabble, Emily (June 20, 2016). "Sarah Crossan wins the Carnegie medal with verse novel One". The Guardian. ISSN 0261-3077. Retrieved April 13, 2017.
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