Ashton Kutcher's recent revelation about his vasculitis diagnosis is bringing to light to an autoimmune disorder that can cause serious damage to the body. "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 That '70s Show alum shared in a preview of his appearance on an upcoming episode of Running Wild with Bear Grylls. "It took me like a year to build it all back up." According to the 44-year-old, he's "lucky to be alive" after battling the rare medical condition. "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?" he told host Bear Grylls. "You start surfing on top of your problems instead of living underneath them." And while Kutcher shared that he's "fully recovered" from his health struggles, his harrowing story shows some of the adverse effects of vasculitis.