In an unfaithful movie version of Finn Miller’s thrilling young life, he might be on a big stage in a packed house, when a word — something vile and not in the script — blurts from his mouth.

Jaws would drop, faces would blanch. The movie would cut to Finn some years later — living on the streets, washed up.

Finn, one of the stars of Joffrey Ballet’s Nutcracker, understands those who may have a distorted view of what he’s been dealing with for much of his life: Tourette’s syndrome, a neurological disorder.

“That’s the Hollywood version of it,” said Finn, 14. “That’s what you always see on TV.”

Finn plays Franz, the younger brother to Marie, the heroine (that’s in Joffrey’s reimagined version — the original names are Clara and Fritz).

Finn doesn’t curse involuntarily, which is true of the vast majority of those with the condition, experts say. But his body sometimes does other things he wishes it wouldn’t. He’s been known to “chirp” — every few seconds for two hours at a stretch. He grunts. He shrugs incessantly. If he’s on a plane, a leg might spasm, drawing glares from the passenger seated in front of him.

Finn Miller plays Franz in Joffrey Ballet's Nutcracker. | Santiago Covarrubias/Sun-Times

Finn Miller plays Franz in Joffrey Ballet’s Nutcracker. | Santiago Covarrubias/Sun-Times

It’s not known exactly what causes Tourette’s, which typically peaks during the teen years and, according to some studies, afflicts as many as one in one thousand people.

“There’s likely a genetic predisposition,” said Dr. Paul Later, a neurologist at Northwestern Medicine Lake Forest Hospital. “Oftentimes, if you delve into it deeply, you get hints of the syndrome in other family members.”

Heightened stress or excitement makes things worse. Odd then that he’d find respite on stage — in front of thousands. In the opening scene of Joffrey’s Nutcracker — now set in 1892 Chicago — only Finn’s witty interpretation of the role and his copper-red hair stands out amid the drab hues of a working-class city.

“When I’m dancing, it doesn’t affect me. I don’t tick. I don’t have the urge or anything,” said Finn, looking utterly at ease during a chat this week as he prepared to go on stage for a matinee performance of the Nutcracker at the Auditorium Theatre.

Dr. Later says Finn’s ability to suppress his symptoms — for a time — isn’t uncommon.

“But then it sort of builds up as tension, like an itch that needs to be scratched,” Later said.

Perhaps it helps Finn that he’s been afflicted with the urge to dance far longer than Tourette’s, first diagnosed when he was eight years old.

“I always just loved to dance anywhere — in stores, at home and basically any time, anywhere,” Finn said.

“Crowded restaurants,” added his mother, Amanda Miller, sitting nearby during his interview.

Finn, a pre-professional student in Joffrey’s academy, has performed on stages big and small, including at The Kennedy Center in Washington D.C. and Lincoln Center in New York.

Miller has been living an itinerant life, traveling to wherever her son’s fledgling career takes them. They’ve been living downtown [close enough to walk to the Auditorium Theatre] since September.

Miller, a portrait photographer, says neither she nor Finn try to hide his condition when he auditions for a new show.

Finn Miller (right) with Anastacia Holden and Matthew Adamczyk (left) in the Joffrey's Nutcracker. | Cheryl Mann photo

Finn Miller (right) with Anastacia Holden and Matthew Adamczyk (left) in the Joffrey’s Nutcracker. | Cheryl Mann photo

“We send out an email at the very beginning, saying, here’s the situation: It’s never affected him on stage, and it doesn’t affect him in rehearsal. But if he has to sit somewhere, like backstage, for two or three hours, he’s probably going to do stuff,” Miller said.

Ashley Wheater, Joffrey’s artistic director, is more familiar with Tourette’s syndrome than most. A few years ago, he was on a flight to New York and ended up sitting next to a boy with the syndrome. Wheater later invited the boy and his family to see Joffrey’s Nutcracker.

So Wheater had no hesitation in choosing Finn as one of two filling the part of Franz in the current production.

“Clearly, he loves to dance,” Wheater said. “You can see that. … I was a little worried that he might be too shy, but he just seemed really engaged and that he wanted to be there, and he’s a striking looking boy.”

It’s not certain how Finn’s Tourette’s might develop in future years. It could lessen or, less likely, worsen.

“It can be annoying,” Miller said. “I love him dearly, but when someone is making a chirping noise every two seconds for two straight hours, I get how that might not be fun in an office cubicle situation.”

But Finn isn’t dreaming of the gray walls of an office cubicle. He sees his future in dance — on stage and perhaps as a choreographer.

“To the end of time,” he says, with a theatrical wave of his hand.

“I don’t really care what the people think of me if I mess up on stage. I’ll just keep going on, doing more shows.”