Hayden Pheif came into this world six years ago at a healthy 7 pounds, 12 ounces, with blond hair and blue eyes. He was the first child born to John and Megan Pheif of Mill Valley, Calif.
"It was, you know, like any normal pregnancy. You're looking forward to the day that you have your first child," Megan Pheif said.
As most parents do with their first child, the Pheifs meticulously documented Hayden's every move. They never noticed anything unusual until Hayden was 2 years old.
"We were ready to go on a camping trip. And we noticed some swelling in his head. And so I took him to the doctor. By the end of the weekend, he couldn't move his neck," John said.
Hayden's story would sound familiar to Anna Marie and Mark Linker of North Carolina. A decade earlier, their baby daughter, Tiffany, was struck with the same strange symptoms, starting when she was 10 months old. Just like Hayden, Tiffany was put through dozens of tests that yielded no diagnosis.
"Tiffany wasn't moving very well. We just knew that something was wrong. We'd continue to go to doctors, and they'd continue to give us advice," said Mark.
Tiffany spent six months in the hospital; she underwent seven surgeries and chemotherapy to remove what doctors believed were tumors.
Suspecting cancer or some other strange disease, doctors continued operating on strange masses on Tiffany's back, but the surgeries failed and the masses kept growing back.
In June 1990, according to her mother, Anna Marie Linker, doctors "sent Tiffany home to die. They said she had two weeks to live." But there was one clue, something that had been overlooked at first: the toddler's big toes.
Hayden's father, John Pheif, remembered a nurse commented that Hayden's toes looked a little bit crooked when he was born. Hayden's toes eventually played a big part in unlocking this medical mystery. When doctors were getting ready to biopsy a mass on Hayden, a nurse overheard the family talking about his odd symptoms.
When she asked if Hayden's big toes were malformed and was told they were, the nurse said Hayden might have a condition called fibrodysplasia ossificans progessiva, or FOP.
Hayden's big toes were the hallmark of this rare and strange disease, of which there are only 2,500 known cases in the world.
Dr. Fred Kaplan, an orthopedic surgeon at the University of Pennsylvania, is the world's leading expert on FOP. "It is a complete and a devastating metamorphosis that just shouldn't take place," Kaplan said. "In FOP, normal skeletal muscle and normal connective tissue turns into bone."
Tiffany was the first child Kaplan had ever examined with the disease.
"I was watching a metamorphosis before my eyes. I was seeing a normal child turn into a child who was imprisoned in a second skeleton -- literally imprisoned in this cage of bone," Kaplan said.
Kaplan has devoted his career to finding a cure for FOP. His office is a testament to all his "children." It's adorned with photos of the 500 kids he has taken care of -- all of them living with this cruel disease. His young patients call him Uncle Fred.
Now Hayden has become one of Uncle Fred's "kids" too. Today, as the disease progresses, Hayden has limited movement in his arms and neck. But flare-ups -- explosive growth of new bone -- can be set off anytime by something as simple as a needle.
"Even seemingly minor things like preschool immunizations, injections for dental work, [or] minor bumps and bruises from falling off a bicycle, can cause these children to lock up their jaw, lock up their joints that never move again," Kaplan said.
Tiffany is now 17 years old and requires an oxygen machine because the extra bone constricting her rib cage doesn't allow her to fully expand her lungs. She knows the next flare-up could rob her of even more mobility.
"A flare-up can happen overnight while you're sleeping. Like, you'll be walking around one day, and you'll go to bed and the next day you won't be able to move. That's how fast it works," Tiffany said.
Tiffany is eager to explain what her life is like to give others a better understanding of what she goes through.
"I would say, let me tie your arms to your sides where you can't move them and then put a neck brace and a back brace where you won't be able to move and then stay in a wheelchair all the time, and then tell me how you feel," Tiffany said.
Today, for the first time, there may be hope for Tiffany, Hayden and other children with FOP. For 15 years, Kaplan has been searching for the gene that causes FOP. Earlier this year, he found it.
The devastation wrought by FOP is caused by the alteration of a single letter of the 6 billion that make up our genetic code.
"It was overwhelming. Finally, we knew the cause of this horrible, catastrophic, disastrous transformation of connective tissue into bone," Kaplan said.
The discovery of this "master switch" will eventually help people with other bone diseases, such osteoporosis, and people who need hip replacements, for which the body needs to make new bone.
Discovering the gene is only half the battle. Now Kaplan is trying to find a cure for FOP. "My lifelong goal since I've started working on FOP is not just to modify the symptoms but to change the course of the disease. And eventually stop it," Kaplan said.
For Tiffany, a cure would mean not losing any more movement. For the Pheifs, it would mean Hayden could have the kind of future his parents originally never thought possible.