Ashton Kutcher has revealed he had an autoimmune disorder that left him unable to walk, see or hear.
Talking on Running Wild with Bear Grylls: The Challenge, Kutcher told Grylls he had had a form of vasculitis that "knocked out" his senses.
Vasculitis is an inflammation of the blood vessels which affects the flow of the blood around the body.
The condition usually targets one organ - rare extreme cases can cause damage to more than one organ at a time.
"Like two years ago, I had this weird, super rare form of vasculitis that, like, knocked out my vision, it knocked out my hearing, it knocked out, like, all my equilibrium," Kutcher said.
Page Six reported he said it took him about a year to regain each sense.
"You don't really appreciate it until it's gone," Kutcher said of his health.
"Until you go, 'I don't know if I'm ever going to be able to see again, I don't know if I'm ever going to be able to hear again, I don't know if I'm ever going to be able to walk again.'
"[I'm] lucky to be alive," he added.
Kutcher said that his run-in with the condition and subsequent recovery had made him re-evaluate his life's problems.
"The minute you start seeing your obstacles as things that are made for you, to give you what you need, then life starts to get fun, right?"
"You start surfing on top of your problems instead of living underneath them."