Most of us would tremble when faced with a venomous spider or a dangerously high cliff edge.
But one woman has a rare disease meaning she is biologically unable to feel fear.
The U.S. woman, known to doctors as SM, has been put into life-threatening situations but remains completely unfazed.
She didn�t panic at being held at gunpoint and knifepoint � and didn�t even call the police after these attacks.
She was also nearly beaten to death by her first husband, but never felt scared.
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