Conjoined twins

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For the Japanese composer Siamese Twin, see AQi Fzono.

Conjoined twins are twins whose bodies are joined together at birth. This happens when identical twin embryos become fused together during the very early stages of development. Contrary to popular belief, conjoined twins are not the result of an incomplete split of twin embryos; rather, the embryos become joined again after they have already split. Conjoined twins occur in an estimated one in 200,000 births, with approximately half being stillborn. The overall survival rate for conjoined twins is between 5% and 25%. Conjoined twins are more likely to be female (70-75%).

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Conjoined Twins in History

The term Siamese Twins comes from what are probably the most famous pair, Chang and Eng Bunker (1811-1874), Chinese brothers born in Siam, now Thailand. The term is frequently used as a synonym for conjoined twins. Chang and Eng were joined by a band of cartilage at the chest (xiphopagus). For many years they traveled with the Barnum circus. In the 1840s they married Sarah and Adelaide Yates of North Carolina and purchased two adjoining farm properties. Together they fathered between 20 and 23 children (accounts vary, and in any case, many of the children passed away in early childhood). In January of 1874, Chang, who was a heavy drinker and had fallen ill with pneumonia, died during the night. Eng also died within a few hours, surrounded by his and his brother's families.

The earliest known case of conjoined twins dates from 945 C.E., when a pair of conjoined twin brothers from Armenia were brought to Constantinople for medical evaluation. The twin sisters Mary and Eliza Chulkhurst, who were conjoined at the back (pygopagus), lived from 1100-1134 and were perhaps the best-known early example of conjoined twins. Other early conjoined twins to attain notoriety were the "Scottish brothers", allegedly twins of the dicephalus type (1460-1488; although the dates vary); Helen and Judith of Szony, Hungary (1701-1723), who were pygopagus twins and enjoyed a brief career in music before being sent to live in a convent; and Ritta and Christina Parodi of Sardinia, born in 1829. Ritta and Christina were dicephalus tetrabrachius 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 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 by England's ban on 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 immoralized 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 two legs and four arms. From birth they were forced by their parents to perform and never learned to walk, as each twin controlled one leg (nowadays physical therapy allows twins like the Toccis to learn to walk on their own). They are said to have disliked showbusiness. 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.

Conjoined twins who appeared in the public eye during the 20th century include Rosa and Josepha Blazek of Bohemia (modern-day Czech Republic; 1878-1922); Lucio and Simplicio Godina of Samar, Philippines (1908-1936); Daisy and Violet Hilton of Brighton, East Sussex, England (1908-1969); Mary and Margaret Gibb of Holyoke, Massachusetts (1912-1967); Yvonne and Yvette McCarther of Los Angeles, California (1949-1992); and Ronnie and Donnie Galyon of Ohio (1951 - ), currently the world's oldest living conjoined twins.

Types of Conjoined Twins

There are several different types of conjoined twin:

  • Thoracopagus: bodies fused in the thorax. The heart is always involved in these cases; when the heart is shared, prospects for a long life, either with or without separation surgery, are poor. (35-40% of cases)
  • Omphalopagus: joined at the lower chest. The heart is not involved in these cases but the twins often share a liver, digestive system, diaphragm and other organs. (34% of cases)
  • Pygopagus (iliopagus): joined, usually back to back, to the buttocks (19% of conjoined twins)
  • Cephalopagus: heads fused, bodies separated. These twins cannot survive due to severe malformations of the brain. Also known as janiceps (after the two-faced god Janus) or syncephalus.
    • Cephalothoracopagus: bodies fused in the head and thorax. These twins cannot survive. (also known as epholothoracopagus or craniothoracopagus)
  • Craniopagus: skulls fused, but bodies separate (2%)
  • Dicephalus: two heads, one body with two legs and two, three, or four arms (dibrachius, tribrachius or tetrabrachius, respectively. Abigail and Brittany Hensel, 15-year-old conjoined twins from the United States, are of the dicephalus tribrachius type.
  • Ischiopagus: Anterior union of the lower half of the body, with spines conjoined at a 180° angle. (6% of cases)
  • Ischio-omphalopagus: Twins are conjoined with spines in a Y-shape. They have four arms and usually two or three legs. These cases can be challenging because the twins often share reproductive and excretory systems.
  • Parapagus: Lateral union of the lower half extending variable distances upward, with the heart sometimes involved. (5% of cases)
  • Diprosopus: One head, with two faces side by side.

In some cases, parts of the brain have been known to be shared between conjoined twins joined at the head.

Occasionally one of the twins will fail to develop properly, effectively acting as a parasite upon the normally developed twin: this condition is known as parasitic twinning or asymmetic conjoined twins. One twin may absorb the other, which is known as inclusion twinning.

Natural death of the twins can occur within hours or a few days.

Separating conjoined twins

Some pairs, depending on the degree of conjunction—in particular, the degree to which they share internal organs—can be separated by surgery.

In July 2003 two 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. Both women died during surgery.

One ethical issue with separation is when the operation will result in the death of one twin (for example, in the case where they are sharing a heart.) A notable case was that of the Attard sisters (Gracie and Rosie), the daughters of Rina and Michaelangelo Attard of the Maltese island of Gozo. The twins were known to the world media as "Mary" and "Jodie" to protect the privacy of the family during their ordeal. Despite the opposition of the Attards, the High Court of Justice of England and Wales ruled that the twins should be separated, even though this would (and did in 2001) cause the death of Rosie ("Mary"), the weaker twin.

Most recently, an attempt was made to separate the German conjoined twins Lea and Tabea Block. Tabea died September 16, 2004 just minutes after having been separated from her twin sister.

Cultural references

Recommended Reading

  • Mutants: On Genetic Variety and the Human Body by Armand Marie Leroi, Viking Books, 2003. This book has a chapter on conjoined twins and provides an excellent description of how they are formed.

See also

External links

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