(WJW) — Actor Ashton Kutcher recently revealed he was diagnosed with an autoimmune disorder that took away his ability to walk, see and hear.

The 44-year-old star opened up about the health scare in an episode of “Running Wild with Bear Grylls: The Challenge,” a show where celebrities adventure with Grylls through the wilderness while learning and applying survival skills.

“Two years ago, I had this weird, super rare form of vasculitis that knocked out my vision, it knocked out my hearing, it knocked out all my equilibrium,” Kutcher said during a portion of the episode, which aired Monday on National Geographic.

Kutcher said it took nearly an entire year to get back to full strength, making clear he’s “lucky to be alive.”

“Don’t really appreciate it until it’s gone,” he told Grylls. “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.'”

Vasculitis causes blood vessels to inflame, according to the Cleveland Clinic, which can lead to aneurysms, thinning of the blood vessels, or the blood vessels can become closed off. The cause of the disorder is unknown but experts say in most cases, something has caused an immune or allergic reaction in the walls of the blood vessels.

This isn’t the Iowa-born celebrity’s first time dealing with major health issues. He also notably ended up in the hospital while filming the Steve Jobs biopic “Jobs” after trying to follow the Apple co-founder’s diet. Drinking mostly carrot juice reportedly gave Kutcher pancreatitis, twice.

He is married to fellow “That ’70s Show” actor Mila Kunis, and the pair have two children.