Doctors report rare case of parasitic twin

The nine-month development of a human fetus is nothing short of wondrous. Equally astonishing, however, are the rare cases in which something in that development goes terribly awry. Doctors in the Greek city of Larissa reported last week that they had successfully removed an embryonic parasitic twin from the stomach of a 9-year-old girl.

The chances of a parasitic twin formation is extremely rare. According to a review of the case published in Medical News Today, it results from the same biological process that produces conjoined twins and vanishing twins (when one twin disappears early in the pregnancy). In the case of a parasitic twin, the twin embryo does not fully separate into two individuals. While one twin develops normally, the other twin is lodged inside the healthy twin.

Early in life, the healthy twin begins to show signs of an abnormal stomach growth and often pain. That's when the parasitic twin, which continues to grow like a tumor from blood supplied by the healthy twin, is discovered. The parasitic twin removed last week was a 2-inch-long embryo. Medical News Today reported one famous case in which a fetus was found in the stomach of a 7-year-old boy because his enlarged stomach showed movement inside. When the parasitic twin was removed, doctors found a nonviable but still highly developed twin brother.

-- Shari Roan