Rare chimera phenomenon makes you split down the middle with two sets of DNA

An NHS surgeon has explained a mind-bogglingly rare condition that makes a person “their own twin” and gives them two different sets of DNA in a single body.

In a video he shared on Instagram, Dr Karan Rajan explains the case of Taylor Muhl who is one of just 100 people in the world with chimerism.

He says: “This woman with a unique birthmark finds out she is her own twin sister.

“Not only does she have this super-cool birthmark exactly in the centre of her body but she’s also got some other quirks.

“Everything on the left side of her body is slightly larger than the right.



Dr Karan Rajan explains human chimerism

“And the left side also has different sensitivities and allergies to insect bites, medication, and food.”

Dr Karan then explained: “She has a super-rare condition called tetragymetic chimerism resulting in one person having two sets of DNA

“This happens when two separate eggs are fertilised by two different sperm and one of the embryos absorbs the other during the early stages of development.

“People with this type of chimerism sometimes have two different eye colours or blood types.



People and animals with chimerism can have different eye colours
People and animals with chimerism can have different eye colours

“It’s so rare there are only 100 recorded cases.”

The video has been watched more than 16,000 times since it was uploaded on Sunday (September 26) and people were amazed.

One user commented: “Whoa. I have a friend with a birthmark that makes her hair half blonde half brown.

“It’s bananas. Split down the middle.”

A second viewer shared: “My son has this EXACT birthmark.

“His left side down to his knee is a different complexion like a straight line separating him.”

Someone else wrote: “I heard of a chimera who temporarily lost custody of her kids because she couldn’t prove she was the mom based on DNA.”

This comes after an awkward typo in a text from an NHS clinic left Reddit users bemused for offering a “free w*** in” – with many joking it would be an incentive for people to get vaccines.

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