What is Celine Dion's Stiff Person Syndrome and what are the symptoms?

The singer Celine Dion announced with a video on her social networks that she suffers from rigid person syndrome.

It is a very rare neurological disease that, according to data from the US National Institute of Neurological Disorders and Stroke, affects more women than men.

She knows in the following video the symptoms of this condition that has no cure.