Parasitic twin removed from brain of one-year-old in China

It was a rare case of fetus-in-fetu -- a congenital abnormality. (Image credit: Neurology journal)

A one-year-old child in China had an unborn parasitic twin removed from her brain, in a rare case of fetus-in-fetu, according to a paper published in the peer-reviewed Neurology journal.

Fetus-in-fetu is a congenital abnormality in which a "parasitic fetus" is situated in the body of its twin. This happens when one of the twins stops developing during gestation and becomes a vestige.

The condition is rare, with only about a 100 cases identified till 2008.

Usually, parasitic twins are found in the retroperitoneal region, which is the area behind the abdomen. But they can be detected in other areas too.

In the one-year-old's case, it was found in the forebrain.

The child had first presented with an enlarged head and motor delay.

After scans and tests, doctors detected a "malformed monochorionic diamniotic twin" in her brain, which was later surgically removed.

"After surgical removal, whole-genome sequencing revealed identical single-nucleotide variants in the host child and fetus-in-fetu," the authors of the study said.

They added that such cases arise from unseparated blastocysts --balls of cells that form during the early stages of pregnancy.

"The conjoined parts develop into the forebrain of host fetus and envelop the other embryo during neural plate folding," they added.

A similar case had been reported in 2015, in a 26-year-old student in the United States. She was diagnosed with teratoma, a growth which had hair and bone, the BBC reported.

Doctors described it as an embryologic twin "extremely deep in the brain".

Fibre optics were used to perform a life-saving surgery on her. The student's insurance didn't fully cover the procedure's cost so a fundraising page was set up for her.