Imagine Dragons star Dan Reynolds' battle with autoimmune condition ankylosing spondylitis cost his band an early record deal, because he couldn't move onstage during a gig.

The record label officials who had come to check out the rockers at the Arizona gig were not impressed by the motionless frontman's performance and decided to pass on the group.

"I was stiff as a board onstage," he tells Billboard. "I could not move and I really thought that was the end of the band.

"It was back when we were looking to get signed and we had at least three different labels in the room and the entire show I just stood exactly still. I did not move and I didn't tell any of the labels that I was in pain, as I was afraid of talking about it at the time. I didn't want them to think that I was going to be some non-performer.

"Somehow we got through the show but none of those labels signed us."

The scare prompted the Believer singer to seek out proper medical help after baffling doctors with his conditions for years.

"I finally went and saw a rheumatologist after a year of seeing a million different doctors and (getting) misdiagnosis (sic). That changed everything. They put me on treatment plan. I changed my diet. I changed my workout regime. It took a lot of work, but (before that) there was definitely a time period where I thought, 'OK, I've worked all this time to make this band happen and now it's going to fall apart...' It was a very scary time period for me."

Dan has now devoted his life to raising awareness about his condition.

"Physically, I have two autoimmune diseases and I want to destigmatize that and raise awareness so that other people don't go through the whole process I did of (seeing) a million different doctors, giving them (the) wrong diagnosis."