Ashton Kutcher Battled Serious Autoimmune Disease

Ashton Kutcher revealed Monday he had battled a serious autoimmune disease that affected his hearing, sight and ability to walk for more than a year.

"Like two years ago, I had this weird, super-rare form of vasculitis," Kutcher said in an exclusive video clip released to "Access Hollywood."

"Knocked out my vision, knocked out my hearing, knocked out like all my equilibrium. It took me like a year to like build it all back up," Kutcher told adventurer and presenter Bear Grylls.

"You don't really appreciate it until it's gone, until you go, 'I don't know if I'm ever gonna be able to see again.

I don't know if I'm gonna be able to hear again, I don't know if I'm going to be able to walk again," Kutcher said. "I'm lucky to be alive."

Vasculitis occurs when the body's immune system attacks veins, arteries and small capillaries.

The resulting inflammation narrows those blood vessels and restricts the flow of blood or even cuts blood flow off entirely, possibly causing organ damage or creating aneurysms.