SUDBURY -- A Greater Sudbury man is sharing his battle with a rare condition that is so painful, it's often called the suicide disease.

Shawn O'Brien has suffered from complex regional pain syndrome, or CRPS, for years. It's a form of chronic pain that usually affects the legs or arms. O'Brien had one of his arms amputated in an attempt to deal with the condition, but it has returned.

"I was in remission for nine months and then in December (it) gradually came back," O'Brien said. "It's in my back. It's in my right arm, my right hand. So basically last week, I spent five days in bed because the pain is just like someone's dipping my whole body in hot lava. I just, I can't move -- it's just too painful to move."

The cause of CRPS is unknown, but it turns the body's defense mechanisms against itself. Receptors that alert you to pain become so sensitive, even a light touch on the skin can cause intense agony.

While it often goes away after several months, in some cases, such as O'Brien's, it can become chronic.

"Now it's it's coming back with gangbusters and I'm afraid it's going to eventually take over my whole body," O'Brien said.

Can't wear artifical arm

He received an artificial arm after his surgery, but the pain has become so severe, he can't wear it.

"So I just gotta' learn to live with this disease and try to bring it to people's attention," O'Brien said.

He's coming forward in hopes of spreading awareness of the condition and to help others avoid the struggle he had getting a diagnosis. It was a doctor in London, Ont., who finally identified what O'Brien was dealing with.

"So at least I got him in my corner realizing what's going on," he said. "I wish more doctors were like him out there."

Because it's such a rare disease that doesn't show up in MRIs or CATS scans, he said many doctors don't realize their patients have it.

"I had emails coming in, (people) thanking me for being a hero … because they've had the disease and no one's believed them," he said. "And now I'm fighting for them."

Living with the disease is not only hard for him, but for his family, O'Brien said.

"I can't make plans to do anything with my wife," he said. "I go day-by-day. (Often) I can't get out of bed and that affects her. She can see me going downhill because this disease is really taking a toll on me.

"I'm not being able to sleep for four or five days. That's taking a toll. So it's really hard on my wife, not just me."

Since he's come forward, other people with CRPS has reached out to him and his story is in a book about the disease available on Amazon.