Ashton Kutcher has revealed he suffered from an autoimmune disorder that took away his ability to see, hear, or walk. In a sneak peek of a new show Running Wild with Baer Grylls: The Challenge, Kutcher opened up about the scary experience. "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," the 44-year-old actor said via Page Six.

He also revealed that it took him about a year for his seeing, hearing, and ability to walk to fully rebuild. According to Mayo Clinic, vasculitis is a very rare autoimmune disorder that can cause inflammation of the blood vessels, which restricts blood flow. Kutcher continued, “You don’t really appreciate it until it’s gone,” Kutcher shared. “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 said.

After recovering from such a serious health scare, Kutcher says no challenge is too big. “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?” said Kutcher, who shares two children with wife and former That '70s Show co-star Mila Kunis. “You start surfing on top of your problems instead of living underneath them.”

Kutcher's episode of Running Wild will air Monday, August 8th, at 9:00 P.M. ET on National Geographic.

Jon Manuel