ELMHURST, Ill. (AP) - Keenan Cahill was just a kid being a kid: lip-syncing to a popular song, goofing around in front of his computer webcam as if the world wasn't watching.
And it wasn't, until Cahill - then an impish 13-year-old with a knack for oddball humor - started uploading his videos to YouTube.
Soon there were hundreds of hits. Then thousands. And eventually millions.
An Internet sensation was born.
"Keenan, what have you done?" his mom asked, when a late-night talk show called and wanted to air one of his lip-syncing videos.
Should she be amused, or horrified? What if people made fun of her son, who has a rare genetic disease that has stunted his growth? What if he'd opened the door to something too big to handle?
For Keenan, though, this was the adventure he'd been waiting for. This was freedom for a young man whose life had, so far, mainly consisted of doctors' visits, when he wasn't going to school or hanging out in his room. A vacation was a trip to a Minnesota children's hospital for surgery on his legs or hips.
Suddenly, he was traveling to places like the Bahamas and France, Los Angeles and Las Vegas. Fans mobbed him as if he were a rock star, their cell phones extended to capture photos and video. And then there were the celebrities who wanted to be seen with him, shoot a video with him.
"I finally got somewhere, out of all the people," says Keenan, now 16.
"I used to pray to God. It's like a switch-back. Now I say "Thank you,' instead of "Can you please get me there?"'
When Keenan was born in 1995, there was little to indicate that anything was wrong. His parents had noticed that his kneecaps were large, but didn't think much about it. Then one day, when he was 6 months old, his mom peered at Keenan in his high chair. His face looked puffy, she thought.
"Honey, are you OK?" she asked.
By age 1, Keenan had fallen off the growth charts. He didn't walk until he was 18 months old, and was prone to worrisome fits of vomiting.
His parents took him to the Mayo Clinic in Minnesota for testing. Doctors also sent a skin graft to a lab in Australia.
The bad news: Keenan had an extremely rare disorder called Maroteaux-Lamy Syndrome, also known as MPS, type 6.
People who have the disease are unable to break down complex sugars called mucopolysaccharides, which accumulate in connective tissue and organs throughout the body. Fewer than 1,100 of people worldwide have the disease, which leads to severe disability and a shortened life span in most cases.
Doctors told Keenan's parents that their son would likely be in a wheelchair by the end of his teenage years if he was not treated. His growth would be extremely hampered, though with this particular type of MPS, there would be no cognitive impairment.
At age 2, Keenan had the first of several procedures and surgeries he would undergo - a life-prolonging bone marrow transplant.
"It was the worst time in my life," recalls his mom, Erin O'Brien-Cahill.
Afterward, Keenan was hospitalized for four months. For a year, he couldn't play with other children or be around other people much to avoid exposure to illness. His mom had to quit her job as a mortgage underwriter to stay in Minnesota with him; his dad, an electrician, got a job at the University of Minnesota.
Family photos show a little boy whose shocks of red hair fell out during treatments, eventually coming back dark brown. Over the years, he would grow to a height of 4-foot-1, leading some to assume that he's younger than he is.
Keenan wears thick glasses that often drop down to the end of his nose. But it's his expressive face and smile - sometimes cheesy, sometimes sincere - that draw people in. He's always loved attention and loved to make people laugh.
Perhaps, he thought, he could be an actor. "I always wanted to be on camera," he says.
His mom took him to talent agencies in the Chicago area. He auditioned a few times, but nothing ever came of it.
"Getting noticed is one in a million," his mom says. "We thought the chances of him achieving his dream were gone."
Then he got a desktop computer with a webcam for his 13th birthday, and a window opened.
Some might snicker at the notion that some kid who shoots low-budget videos in his bedroom is a star. But judging from the fervor of those who try to reach out to Keenan, the phenomenon is real.
"It's completely redefined the definition of celebrity," says Victor Mehren, a senior marketing director at the Wrigley Co., which hired Keenan to appear in an online advertisement for Juicy Fruit gum. He stars with a singing unicorn puppet.
Keenan hesitates to call himself a celebrity. His manager says he shouldn't even say the words "celebrity" or "fame."
"I need to stay grounded," he says.
He talks about backup plans and college. He shrugs nonchalantly when people ask if schoolmates give him extra attention. "Not really," he says. "Kids know about it, but they don't make a big deal."
Truth be told, though, Keenan is enamored with his new life. He checks his YouTube and Twitter stats. He monitors his cell phone constantly for news about his next public appearances, scheduled - at his mom's insistence - on weekends and vacations so he doesn't miss school.
He's helped open a teen club in the Bahamas. He's shot a commercial with actress Jennifer Aniston, which has gotten more than 8 million hits. He's done videos with rapper 50 Cent and "Jersey Shore" star DJ Pauly D, among others.
He's also joked comfortably with comedian Chelsea Handler on her late-night talk show, giving her his phone number and calling her a "cougar" who preys on younger men.
And when Keenan turned 16, pop star Katy Perry enlisted other celebrities to join in sending him a video greeting.
Keenan's never met Perry, but he says she's his mentor, the one who sent his life into an upward spiral last fall with a simple posting on Twitter after she saw a video of him lip-syncing to her song "Teenage Dream."
"I heart you (at)KeenanCahill," the tweet read.
Keenan had already been getting attention, but this took it to a new level. The emails and phone calls poured in.
It was too much to handle. So when David Graham and Mark Long, who got their start in reality TV, approached Keenan and his mom about being on one of their shows, his mom asked if they would serve as his managers.
"When Mark and I got Keenan, we said, "OK, we're going to set this kid up right from day one,"' says Graham, who's based in Las Vegas.
No drinking and no partying, they said - rules that were no problem for a kid who seems to have no interest in that, anyway.
And no appearances on B-level talk shows. "He doesn't need that, doesn't need to be overexposed," says Graham, who's focused more on videos with celebrities, ad deals and club appearances. Several of the artists Keenan has done videos with work with EMI Records, Perry's label. Keenan also has recorded his own song - one in which he actually sings - set for release this spring or in early summer.
It sounds like it might be lucrative, but the financial rewards are not that great, Graham says.
"He's not going to be able to retire off this. This is more or less a cool after-school job," he says. "For him to really cash in, he'd have to land a TV show or a movie."
That's Keenan's big hope - that this attention will lead to a sitcom. But Graham isn't sure that will happen.
"I don't want Keenan to go to LA and experience failure. I want him to come there, shoot something and go home," Graham says. "I don't want him to have a TV show that fails and have him go back to school and everyone makes fun of him."
During the telephone interview, Graham pauses a few times to answer messages from Keenan, who is texting on his lunch hour at school.
"It's like having a child," Graham says. "He's constantly asking questions."
Keenan's mom, who's back working in the mortgage insurance industry, continues to shake her head at all this, though usually with a smile. Her boy is happy, and that makes her happy.
"It's insanity," she says, "but a good insanity."
Even she can't quite wrap her head around the mania surrounding her son when he lip-syncs at live performances.
"You'd think Barbra Streisand was singing. It's like, really? For real?" she says as she sits in the suburban Chicago town house she and Keenan share with his younger sister. Keenan's parents divorced five years ago (his dad accompanies him to some of his engagements).
It is, indeed, quite a heady and sometimes bizarre scene for a 16-year-old. Keenan is whisked in and out of nightclubs, where he usually can't stay too long because he's underage. He signs autographs. He poses for photos with Playboy bunnies in Las Vegas, baseball players at spring training in Arizona, people on the street who stop him.
One club in Israel hosted a "Keenan Cahill Worshipping Party" late last year. Keenan wasn't able to attend, so partygoers danced with posters of him, instead.
"He's amazing. He's so sexy. I love him!" one of them said, in a video recorded at the event.
"I think he's one of the most important artists of our time," said another.
To these people, Keenan appeared to be a curiosity, almost a pop culture caricature of himself.
Some would call it playful fun. But it's gone well beyond that on his YouTube page, where the comments are sometimes harsh. People have called him everything from a "rent-a-dwarf" to a "freak," and worse, though those comments often send his fans rushing in to defend him.
Some question whether the celebrities who do videos with Keenan are really just using a naove teenager and, unwittingly or not, turning him into a side show.
But Keenan doesn't think so. Nor do others who've tracked YouTube phenoms.
"We think that about child stars: "Oh, he's being used. He's being abused. People are taking advantage of him.' Why that hasn't been a problem so far (with Keenan) is that he seems to be enjoying himself," says Kelly O'Keefe, a professor of brand management at Virginia Commonwealth University.
"He put himself out there. Now he's living a dream and getting to meet celebrities."
Through it all, Keenan undergoes weekly infusions - enzyme replacement therapy - that doctors hope will stabilize his disorder and extend his life. This summer, he will undergo hip and leg surgery; during his weeks-long recovery, he will have to stop making appearances.
If the state of his health is uncertain, the prognosis for his improbable career is even more so.
"These phenomena don't have forever staying power. At some point, his 15 minutes of fame may well be over," O'Keefe says.
Graham, Keenan's manager, says he'd be happy if it lasted through high school and long enough to pay for a special car that allows people who aren't very tall to drive.
His mom says, "Whatever it is will be OK," though she knows Keenan dreams of more.
"I don't like talking about the end," he admits.
With that, he asks if he can be excused from an interview. "Are we done?"
His mom tells him to stay put, but he stands up, flashes that cheesy smile and slowly sidesteps away, so he can go back upstairs to his bedroom.
And his computer.
Keenan's website: http://www.keenansroom.com
Birthday video: http://bit.ly/gnrQbU
Aniston commercial: http://bit.ly/hiZO6w
Martha Irvine is an AP national writer. She can be reached at email@example.com