Shanghai doctors were perplexed with two-month-old boy, who was born with an extra arm, and were left clueless about the cause of his deformity.
The boy was taken to the Shanghai Children's Medical Centre, one of China's top hospitals for treating congenital deformities, but the doctors were unsure which of his two left arms was his stronger one and when they would be able to operate on him, the Shanghai Daily said.
"I have never seen such a patient before," the newspaper quoted Chen Baocheng, director of the centre's orthopaedics department, as saying.
"We don't know the cause of the deformity," he said.
Chen said the doctors were likely to remove one of the left arms and try to preserve normal functions in the remaining one.
"He may need a series of operations," he was quoted as saying.
Other reports said surgery on the boy, named Jie Jie, might have to be delayed until he is older.
Pre-operative tests required to ensure the success of the surgery were difficult to perform on such a young child, they said.
Jie Jie is the first child of two farmers in Anhui Province, close to Shanghai.
Preliminary examinations at the hospital also found that Jie Jie had only one kidney.
He is "in stable condition in the intensive care unit", the newspaper said.
His mother was unaware of his deformity before his birth, as it was not detected by two "simple prenatal examinations", it said.
"It wasn't until my son was delivered after a Caesarean operation that we knew he had three arms," it quoted his unnamed 22-year-old mother as saying.