Graveyard Shift

Parasitic Evil Twins: The Bizarre And Dangerous Fetus In Fetu Syndrome

Parasitic twins are often the subject of cheesy horror flicks or macabre urban legends. But these over-the-top stories about twins have their roots in a very real medical phenomenon: fetus in fetu syndrome, which experts at the National Center for Biotechnology Information, or NCBI, have described as "a rare condition that has been defined as the presence of one twin in the body of the other."

This medical oddity happens in the womb. Two babies will begin to grow until eventually, a dominant one will begin to "absorb" the other into its body. Usually, fetus in fetu syndrome is diagnosed only after the surviving twin is born. But in some rare - and grisly - cases, the remains of the absorbed twin aren't discovered until much later.

So, what do these parasitic twins look like? Sometimes the encapsulated twin is astonishingly developed and lifelike, and sometimes it resembles a medical illustration gone wrong. Whatever form it takes, this mysterious medical condition is as fascinating as it is tragic.