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Parasitic Twins
By William Lee
More than a century before little Lakshmi Tatma and the complex operation to remove her parasitic twin made headlines, people around the world were awed and fascinated by another young Indian marvel. Laloo, as he was known, was born in 1874 in Oudh, India, with an undeveloped twin brother two arms, two legs, a urinary system and genitalia attached to his breastbone. In Laloos day, doctors had no way to fix his problem, but somehow, he not only survived, but made the best of his fate. The strangest man in India, as he was billed, became a star attraction in the sideshows that once travelled with Victorian-era circuses. To shock and puzzle audiences even further, he sometimes dressed his parasitic twin as a girl. He reportedly became a wealthy man from the fees for his exhibitions, married a woman with conventional anatomy, and even campaigned for more dignified treatment of performers with disabilities like his, before dying in a train accident in Mexico in 1905.
Different as their stories are, Lakshmi and Laloo both exemplify the strange phenomenon of the parasitic twin, and the curious tangle of emotions and wonder that it has long evoked. In ancient times, parasitic twins may well have provided the inspiration for deities such as Janus, the two-faced Roman god, and Vishnu, the four-armed creator and destroyer of Hindu mythology. Even today, they continue to appear in works of science fiction and fantasy most notably, the Martian rebel leader and clairvoyant Kuato, who emerges from his twin brothers abdomen in the 1990 hit movie Total Recall. Meanwhile, generations of medical researchers have struggled to understand why the peculiar abnormality occurs, and what might be done to remedy it, since real-life humans born with parasitic twins have long faced slim odds of survival. But today, surgical advances offer the possibility that Lakshmi and others with her condition may actually lead normal lives.
Parasitic twins begin much the same way as healthy identical, or monozygotic, twins. A single fertilized egg, or zygote, splits into two cell masses which go on to become identical embryos. In rare instances, the two cell masses do not fully separate. Sometimes, the result is a pair of identical twins with mostly normally developed bodies that are fused together. The most famous example of such conjoined twins is Chang and Eng Bunker, born in 1811 in what is now Thailand. The brothers were linked at the sternum by a small piece of cartilage and had connected livers, but otherwise had complete, functional bodies. (Like Laloo, they became well-paid sideshow attractions and eventually relocated to North Carolina, where they owned a plantation and fathered 22 children, before expiring on the same day in 1874.) By various estimates, such conjoined twins occur once in every 50,000 to 200,000 births. In recent years, improved surgical techniques have enabled doctors to successfully separate conjoined twins who do not share too many vital organs. In 1997, for example, British doctors were able to part two Irish sisters, Aoife and Niamh McDonnell, by using an ultrasonic tool to divide their common liver. A decade later, the pair are growing up as normal schoolchildren.
In other, even rarer cases no statistical estimates seem to be available something called asymmetric disomata occurs. Essentially, one of the conjoined twins stops developing. How or why this happens is not yet understood, though some medical experts have theorized that the parasitic twins circulatory system atrophies, leading to a reversal in which it is supplied with deoxygenated blood from the normal twin. The inchoate parasite remains fused to the larger, otherwise normally formed twin, which is called the autosite.
There are different types of parasitic twins. Cephalophagus parasiticus is a parasitic twin that consists of mostly a head, attached to the head of the dominant twin. Other variations include epignathus parasiticus, in which a parasitic twin is attached at the jaw; pygopagus parasiticus, which is joined at the buttock; and thoracopagus parasiticus, which is fused at the chest or back. Yet another type of parasitic twin is a fetus-in-fetu, or inclusion twin, which actually develops inside the abdominal or thoracic cavity or elsewhere inside the body of the dominant twin. It can range in development from a shapeless mass of tissue to a fairly well-developed twin.
Parasitic twins have a variety of deformities and missing organs. A parasitic twin attached to the base of the spine of a Turkish child, as described in the medical journal BMC Pregnancy Childbirth, had short, misshapen legs and three toes on one foot. In another case, documented in the Internet Journal of Surgery, an Indian infants parasite had well-formed legs and genitalia, but only a single, underdeveloped arm and a single kidney. The New York Times reported a case in 2000 of a Puerto Rican child and her underdeveloped twin who had an abnormality called twin-reversed arterial perfusion (TRAP), in which the parasite failed to develop its own heart and depended upon the normal twin to pump blood through its body.
Despite medical advances, children born with parasitic twins face an uncertain survival rate. In one case described in the Journal of Internet Surgery, surgeons were able to successfully remove the trunk, limbs and organs of a parasitic twin from the healthy one, and the child was healthy enough to be discharged from the hospital nine days later. But in a second case documented in the article, they successfully removed a parasitic twin that shared a liver, but the child that remained later died of heart failure.
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