Rare Diagnosis 'Knocked Out' Ashton Kutcher's Vision, Hearing

Ashton Kutcher has revealed for the first time that a rare diagnosis two years ago left him unable to see, hear, or walk. "I had this weird, super rare form of vasculitis," the actor says on an upcoming episode of Running Wild With Bear Grylls: The Challenge that was previewed by Access Hollywood. "You don't really appreciate it, until it's gone," Kutcher said of his senses and health, per Yahoo News. "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.'"

He says it took nearly a year for him to regain his ability to walk, see, and hear. Vasculitis is an autoimmune disorder in which the immune system attacks the body's own veins, arteries, and small capillaries, resulting in inflammation of the blood vessels. As a result, blood flow is restricted or cut off, and organs can be damaged. The 44-year-old says he's "lucky to be alive" after battling the rare disease. As CNN reports, it was complications from a form of vasculitis (there are multiple types) that killed director Harold Ramis at age 69. (More Ashton Kutcher stories.)