Conjoined twins (also known as Siamese twins) are identical twins whose bodies are joined in utero. A rare phenomenon, the occurrence is estimated to range from 1 in 50,000 births to 1 in 100,000 births, with a somewhat higher incidence in Southwest Asia and Africa.^[1] Approximately half are stillborn, and a smaller fraction of pairs born alive have abnormalities incompatible with life. The overall survival rate for conjoined twins is approximately 25%.^[2] The condition is more frequently found among females, with a ratio of 3:1.^[1]

Two contradicting theories exist to explain the origins of conjoined twins. The older and most generally accepted theory is fission, in which the fertilized egg splits partially. The second theory 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 that also share these structures in utero.^[3]

The most famous pair of conjoined twins was Chang and Eng Bunker (Thai: อิน-จัน, In-Chan) (1811–1874), Thai brothers born in Siam, now Thailand. They traveled with P.T. Barnum's circus for many years and were billed 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.^[4] Due to the brothers' fame and the rarity of the condition, the term came to be used as a synonym for conjoined twins.^[5]

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:

• Thoraco-omphalopagus (28% of cases):^[6] 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.^[7]
• Thoracopagus (18.5%):^[6] Two bodies fused from the upper thorax to lower belly. The heart is always involved in these cases.^[7]
• Omphalopagus (10%):^[6] Two bodies fused at the lower chest. Unlike thoracopagus, the heart is never involved in these cases; however, the twins often share a liver, digestive system, diaphragm and other organs.^[7]
• Parasitic twins (10%):^[6] Twins that are asymmetrically conjoined, resulting in one twin that is small, less formed, and dependent on the larger twin for survival.
• Craniopagus (6%):^[6] Fused skulls, but separate bodies. These twins can be conjoined at the back of the head, the front of the head, or the side of the head, but not on the face or the base of the skull.^[7]

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. Also known as janiceps (after the two-faced god Janus) or syncephalus.^[7]
• Synecephalus: One head with a single face but four ears, and two bodies.^[7]
• Cephalothoracopagus: Bodies fused in the head and thorax. In this type of twins, there are two faces facing in opposite directions, or sometimes a single face and an enlarged skull.^[7][8]
• Xiphopagus: Two bodies fused in the xiphoid cartilage, which is approximately from the navel to the lower breastbone. These twins almost never share any vital organs, with the exception of the liver.^[7] 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; two, three or four legs; and typically one external set of genitalia and anus.^[7]
• Omphalo-Ischiopagus: Fused in a similar fashion as ischiopagus twins, but facing each other with a joined abdomen akin to omphalopagus. These twins have four arms, and two, three, or four legs.^[7]
• Parapagus: Fused side-by-side with a shared pelvis. Twins that are dithoracic parapagus are fused at the abdomen and pelvis, but not the thorax. Twins that are diprosopic parapagus have one trunk and one head with two faces. Twins that are dicephalic parapagus have one trunk and two heads, and two (dibrachius), three (tribrachius), or four (tetrabrachius) arms.^[7]
• Craniopagus parasiticus: Like craniopagus, but with a second bodiless head attached to the dominant head.
• Pygopagus (Iliopagus): Two bodies joined at the pelvis.^[7]

Separation

Surgery to separate conjoined twins may range from relatively simple to extremely complex, 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. This makes the ethics of surgical separation, where the twins can survive if not separated, contentious. Dreger found the quality of life of twins who remain conjoined to be higher than is commonly supposed.^[9] Lori and George Schappell are a good example.

A case of particular interest was that of Mary and Jodie, two conjoined twins from Malta who were separated by court order in Great Britain 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 it was certain that the weaker twin, Mary, would die as a result of the procedure. (The twins were attached at the lower abdomen and spine; Jodie's heart and lungs supplied both of their bodies.) However, if the operation had not taken place, it was certain that both twins would die.^[10][11]

Conjoined twins in history

(1493).]]

Lima, Peru.]]

The Moche culture of ancient Peru depicted conjoined twins in their ceramics dating back to 300 CE.^[12] The earliest known documented case of conjoined twins dates from the year 945, when a pair of conjoined twin brothers from Armenia were brought to Constantinople for medical evaluation. It was here that they were determined to be acts of God and the birth of conjoined twins was considered a proof that the male's sexual prowess was truly twice that of the average man.

The English twin sisters Mary and Eliza Chulkhurst, who were conjoined at the back (pygopagus), lived from 1100 to 1134 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.

]]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.

The life of Abd Manaf ibn Qusai includes a legend that he separated his conjoined sons with a sword.

The Muslim polymath Abū al-Rayhān al-Bīrūnī described Siamese twins in his book Kitab-al-Saidana. (973-1048)^[13]

List of conjoined twins

Bold = have been separated.

Born 19th century and earlier

• Mary and Eliza Chulkhurst (1100–1134) (also known as the Biddenden Maids) from England. They are the earliest set of conjoined twins whose names are known.
• Lazarus and Joannes Baptista Colloredo (1617-164?)
• Helen and Judith of Szony (Hungary, 1701–1723)
• Chang and Eng Bunker (1811–1874), from Thailand (formerly Siam), joined by the areas around their xiphoid cartilages, but over time the join stretched; the expression Siamese twins is derived from their case
• Millie and Christine McCoy (July 11, 1851 - October 8, 1912) were American conjoined twins who went by the stage names "The Two-Headed Nightingale" and "The Eighth Wonder of the World".
• Giacomo and Giovanni Battista Tocci (1875?-1912?)
• Rosa and Josepha Blazek of Bohemia (modern-day Czech Republic (1878–1922)). Rosalie gave birth in 1910 to a son, in the only recorded instance of a conjoined twin becoming pregnant and carrying a child to term.^[14]
• Radica and Doodica were born in Orissa, India in 1888. They were xiphopagus twins, joined at the chest by a band of cartilage, similar to Chang and Eng. The sisters were separated in Paris by Dr. Eugène-Louis Doyen with the hope of saving Radica. Dr. Doyen was a pioneering medical filmmaker and filmed the twins' surgery as La Separation de Doodica-Radica. Though the operation was considered a success at first, Doodica died shortly after separation, and Radica also succumbed to tuberculosis in 1903, having lived the last year of her life in a Paris sanitorium.^[15]

Born 20th century

• Ganga and Jamuna Mondal (1969/1970-), the "spider girls" of Basirhat, West Bengal, India[1].
• Daisy and Violet Hilton of Brighton, East Sussex, England (1908–1969), born in England, lived in United States, actresses, appeared in the movies Freaks and Chained for Life;
• Lucio and Simplicio Godina of Samar, Philippines (1908–1936);
• Mary and Margaret Gibb of Holyoke, Massachusetts (1912–1967);
• Juraci and Nadi Climerio de Oliverras (1957–1974)
• Yvonne and Yvette McCarther of Los Angeles, California (1949–1992);
• Masha and Dasha Krivoshlyapova (ischiopagus tripus) Moscow, Russia (1950–2003), Soviet/Russian twin girls, rarest form of conjoined twins, only known case of dicephalus tetrabrachius tripus (two heads, four arms, three legs). The third, fused leg was amputated when the twins were 16 or 17.
• Lotti and Rosemarie Knaack (craniopagus) born in Hamburg, Germany in 1951. Separated in 1957 when they were nearly six years old. Lotti died in surgery.^[16]
• Ronnie and Donnie Galyon of Ohio (1951–), currently the world's oldest living conjoined twins.
• Lori and George (formerly Reba, born Dori) Schappell born 18 September 1961 in Reading, Pennsylvania, American entertainers, craniopagus.
• Sherrie and Sharise Jones born on June 15, 1967 and successfully separated on November 13, 1968 in Brooklyn, New York, ischiopagus tripus conjoined twins^[17]
• Ladan and Laleh Bijani of Shiraz, Iran (Persia) (1974–2003); died during separation surgery in Singapore
• Viet and Duc Nguyen, born on February 25, 1981 in Kon Tum Province, Tây Nguyên, Vietnam, and separated on October 4, 1988 in Ho Chi Minh City. Viet died on October 6, 2007.
• Ruthie and Verena Cady, born April 13, 1984, thoracopagus twins. Died of heart and respiratory problems July 19, 1991.^[18]
• Hassan and Hussein Salih, born August 21, 1986, (Omdurman, Sudan/London, England (UK) - Separated April 1987 at Great Ormand Street Children's Hospital - Survived.
• Katie and Eilish Holton of Kildare, Ireland, babies born joined at the shoulder in 1988. They were born with separate heads and necks but their bodies were joined from the shoulders down. Katie died a few days after separation in 1992.^[19]
• Abigail and Brittany Hensel, born March 7, 1990 in Carver County, Minnesota, United States of America, dicephalic conjoined twins, two heads, two arms, two legs, cannot be separated
• Iesha & Teisha Turner, born April 19, 1991 Successfully separated at Texas Children's Hospital^[20]
• Gita & Zita Rezekhanova, born October 19, 1991 Successfully separated in Moscow, Russia
• Ram & Laxman 1992 Successfully separated at Guntur, India
• Anjali & Geetanjali 1993 Successfully separated at Guntur, India
• Rekha & Surekha 1998 Successfully separated at Guntur, India
• Shawna and Janelle Roderick (thoracopagus) separated May 31, 1996^[21] at Loma Linda Children's Hospital.^[22]

Born 21st century

• Carmen and Lupita Andrade, born Dicephalus Tetrabrachius Dipus (2 heads, 4 arms and 2 legs) in 2000. Separation was not possible.
• Ganga and Jamuna Shreshta of Nepal, conjoined twins born May 9, 2000 who were separated in a landmark surgery in Singapore in 2001; Ganga died on July 29, 2008 at the age of 8 of a chest infection;^[23]
• Rose and Grace Attard ("Mary and Jodie"), Maltese twins joined at spine, born October 2000. Separated in Great Britain by court order against the wishes of their parents, because Mary could not survive independently.^[24] Mary died upon separation.
• Ayşe and Sema born in Kahramanmaraş, Turkey on December 24, 2000 with 2 heads, 4 arms and 2 legs.^[25]
• Lexi and Syd Stark Born in 2001, successfully separated later.
• Mohamed and Ahmed Ibrahim, born in a small Egyptian town on June 2, 2001, separated in a 34-hour operation at Children's Medical Center Dallas on October 12, 2003
• Carl and Clarence Aguirre, born in Manila on April 21, 2002 were successfully separated using a staged procedure performed over the course of 10 months at the Children's Hospital at Montefiore in New York City. The separation occurred on August 4, 2004.^[26]
• Kendra and Maliyah Herrin ischiopagus twins separated in 2006 at age 4. Born with only one kidney between the two, Maliyah received a kidney transplant from her mother in 2007. The twins' mother then wrote a book about her experiences titled "When Hearts Conjoin", the only book about conjoined twins written by a parent of conjoined twins.^[27]
• Zoe & Ana (born in 2003) conjoined at the head and successfully separated in Rome in October 2003.^[28]
• Leah & Tabea B. born in 2003 in Lemgo/Germany, conjoined at the head, separated in Baltimore in 2004. Tabea died shortly afterwards.
• Anastasia and Tatiana Dogaru, born outside of Rome, Italy on January 13, 2004. As Craniopagus twins, the top of Tatiana's head is attached to the back of Anastasias's head. Although Anastasia is the bigger twin, she has no kidney function and relies enirely on Tatiana's kidneys. Due to the degree of their connection, they cannot be separated.
• Sarah and Abbey (Pygopagus) born in New Zealand in 2004 and separated successfully later that year.
• Veena & Vani 2004 Successfully separated in Guntur, India.
• Lakshmi Tatma (born 2005) was an ischiopagus conjoined twin born in Araria district in the state of Bihar, India. She had four arms and four legs, resulting from a joining at the pelvis with a headless undeveloped parasitic twin. Some of the local villagers have hailed her as the reincarnation of Lakshmi, the multi-limbed Hindu goddess. In November 2007 she successfully underwent surgery to remove the parasitic twin.^[29]
• Jade and Erin Buckles, born February 26, 2004, United States. Separated in June 2004.^[30]
• Emma and Taylor Bailey were born September 20, 2006 and died after complications encountered during surgery to increase the pressure in their shared heart on August 10th, 2010.^[31]
• Krista and Tatiana Hogan, Canadian twins conjoined at the head. Born October 25, 2006.
• Trishna and Krishna from Bangladesh were born around December, 2006, joined on the tops of their skulls, and sharing a small amount of brain tissue. They were found in an orphanage, and their surname is not clear. On 16–17 November 2009, they were separated in Melbourne, Australia, in a 32-hour operation involving a surgical team of 16 led by Wirginia Maixner, director of neurosurgery at the Royal Children's Hospital in Melbourne. Doctors had not only to separate shared brain tissue, but perform plastic surgery to close up the girls' skulls. A series of earlier operations had been performed to separate shared blood vessels and to insert tissue expanders in preparation for the final separation.
• Alex and Angel Mendoza were born in the summer of 2008 and were joined from below their sternums to their pelvises. They were successfully separated in January 2009.^[32]
• Faith and Hope Williams born in London, England, on 26 November 2008; The girls were joined from the breastbone to the navel. On 2 December 2008 they underwent an operation to separate them at Great Ormond Street Hospital in London.^[33] On 3 December Hope died. Faith died 23 days after her sister on Christmas Day, with her parents at her bedside.^[34]
• Jayden and Joshua Chamberlain were born in July 2009 in London, joined face to face with a shared liver and fused heart. Joshua was stillborn and Jayden died 30 minutes after the birth. Separation was previously considered too risky to undertake due to the extent at which the boys' hearts were connected.^[35]
• Milagros and Ruth Guelac born in Lima, Peru on October 22, 2009. They shared one heart and intestines, so they were impossible to separate.
• Hassan and Hussein Benhaffaf were born on January 15, 2010 at University College Hospital, London and then transferred to Great Ormond Street Hospital, London where they were successfully separated in March 2010. Their parents are natives of Cork, Ireland.^[36]
• Kauany Aparecida and Keroly Joice born in Campo Grande, Brazil on March 5, 2010. They share one thorax and one abdomen.^[37][38]
• Hanna Yaneth and Hanna Yineth born in Panama. They shared the liver and were connected though the abdomen. They were separated successfully on 28 September 2010. Hanna Yineth's kidney never worked after the separation and on October 10th died as a result of a cardiac arrest.

Conjoined twins in popular culture

• Tim Burton 2003 film Big Fish stars twin sisters Ada and Arlene Tai as conjoined twins, Ping and Jing.
• 1950s comic stories published by EC Comics often featured conjoined twins, usually revealed in a surprise twist ending.
• The 1973 independent film Sisters features conjoined twins who were previously separated.
• In 1997 the Broadway Musical Side Show, by Bill Russell and Henry Kreiger, features real life conjoined twins Daisy and Violet Hilton. Alice Ripley and Emily Skinner started as Violet and Daisy, respectively.
• The 1997 video game Blade Runner features conjoined twin characters Luther and Lance, who may or may not be replicants.
• The 1998-2001 TV show CatDog starred conjoined twins of a cat and a dog.
• The 1999 film Twin Falls Idaho centers on reclusive conjoined twin brothers.
• The 2003 film Stuck on You stars Matt Damon and Greg Kinnear as non-identical conjoined twins, a medical impossibility (or at least, there is no recorded case).
• The 2005 mockumentary Brothers of the Head follows conjoined twin brothers who form a rock band.
• The 2005 book The Girls by Lori Lansens, which is a fictional autobiography of craniopagus twins
• The Hindi serial Amber Dhara, which aired on Sony Entertainment Television India from September 24, 2007 to April 24, 2008, was about two conjoined sisters named Amber and Dhara.
• In the DC Comics, Aromin & Gasser are often referred to as conjoined twins
• Evelyn Evelyn are a musical duo formed by Amanda Palmer (of The Dresden Dolls) and Jason Webley. According to the fictional backstory described by Palmer and Webley, the duo consists of conjoined parapagus tripus dibrachius twins (attached at the sides sharing two arms and three legs) "Eva" and "Lyn", aka Evelyn and Evelyn Neville, who were discovered in 2007 by Palmer and Webley. The twins are actually portrayed by Palmer and Webley.
• In the Courage the Cowardly Dog episode "The Quilt Club", there are conjoined twin sisters named the Stitch sisters who try to initiate Muriel into a "Quilt Club" when in reality, they wish to seal her into a possessed quilt where she'll forget everything about her life.

See also

• Medical law
• Monoamniotic twins
• Polycephaly

References

External links

• National Guard Hospital- Saudi Arabia
• Types and social history of conjoined twins
• The site of the medical Saudi team responsible for the numerous successful separation surgeries
• Eng and Chang - The Original Siamese Twins; The University of North Carolina at Chapel Hill, The North Carolina Collection Gallery
• The Human Marvels: A Historical Reference Site run by J. Tithonus Pednaud, Teratological Historian
• Cases of conjoined and incomplete twins
• Clara and Alta Rodriguez, joined at the pelvis and successfully separated in 1974 at Children's Hospital of Philadelphia by surgeons including C. Everett Koop
• National Library of Medicine: Selected Moments in the History on Conjoined Twins
• Emedicine article
• Facts About Multiples: Conjoined Records and stats

Conjoined twins, also known as Siamese Twins are twins whose bodies are joined together at birth. This happens where the zygote of identical twins fails to completely separate. Conjoined twins occur in an estimated one in 200,000 births, and approximately half are stillborn. The overall survival rate for conjoined twins is between 5% and 25%. Conjoined twins are more likely to be female (70-75%). Daisy and Violet Hilton are a famous pair of conjoined twins. They were born in Brighton and were kept on top of the Evening Star pub, where they were taught to dance by a cruel barmaid. She then sold them and they toured Vaudeville. They became famous in the movie Freaks and lived long lives, eventually getting married.