A six-month-old baby girl has undergone an operation to remove her second mouth, which was complete with lips, teeth and tongue.
When the mass was first spotted in scans at week 28 of pregnancy it was thought to be a possible cyst or tumour.
But when the little girl was born in Charleston, South Carolina, doctors found the 0.8-inch object was actually a second mouth.
She is one of just 35 people known to have suffered from Diprosopus - or duplication of facial parts - since 1900.
Writing in the journal BMJ Case Reports, the doctors said her second mouth had no connection to the main mouth, and that she could breath, eat and drink normally.
They added it would sometimes produce a clear liquid - possibly saliva - and at times a raw surface would appear around it.
The little girl was admitted for surgery so the extra organ could be removed. This involved drilling down on her mandible to remove extra bone supporting teeth for the other mouth.
'After surgery, she developed some mild fullness of the right face at the surgical incision for which a scan was performed, revealing a fluid collection,' the doctors said in their paper.
'The fullness resolved over several months and she did not require further treatment.
'At the six-month follow-up, the incisions were well-healed and the patient was feeding without difficulty.'
But they also noted she was unable to move the right lower lip downwards, which could mean muscles in that area are no longer working.
Diprosopus, which has also been recorded in chickens, sheep, cats and other animals is an extremely rare condition.
Scientists said it results from problems in proteins signalling facial structure during pregnancy, which can lead to a widening of facial features and duplication of their structures.
A boy was born in Missouri in 2004 who had a large cleft, two separate nostrils and an abnormally shaped head due to the condition.
Tres Johnson amazed doctors, who didn't expect him to live, to celebrate his 13th birthday in 2017.
This article has been adapted from its original source.
