This is the fate of those with fibrodysplasia ossificans progressiva (FOP), one of the rarest, most disabling genetic conditions, in which inflammation causes the body's soft tissues to turn to bone, slowly trapping victims in a second skeleton.

Ashley Kurpiel, 28, from Peachtree City, Ga., has battled FOP since she was diagnosed at age 3 -- just five months after doctors mistakenly amputated her right arm, on the assumption that the growths caused by FOP were cancerous tumors.

"Ninety percent of [FOPers] get misdiagnosed with some form of cancer," Kurpiel says.

Some undergo needless chemotherapy, biopsies, or surgeries, all of which worsen the condition -- causing more inflammation and consequently, more bone.

There are believed to be 700 patients with FOP around the globe. For them, something as simple as a visit to the dentist, a fall, or an immunization shot can lead the joints to lock up -- sometimes overnight -- never to move again.

"I can't move my left arm from my side at all, I have very little neck movement, no lower back movement at all, my right hip is affected, and my upper back is really stiff," Kurpiel says.

The condition slowly freezes up the victim's body, but trauma, infection, or any cause for inflammation can speed the progression, precipitating a painful flare-up and leading to further bone growth and disability.

"The worst flare-up I had was my upper thigh at age 25. The whole leg was red and swollen, I couldn't move, it was insanely painful," Kurpiel says.

Currently there is "no real treatment to cure or significantly change the course of the disease," says Dr. Eileen Shore, a research associate professor of orthopedic surgery at the University of Pennsylvania, who has studied the disease since 1991.

Steroids can be administered at the first signs of a flare-up to reduce the inflammation, but the success of this treatment is limited and varies greatly from patient to patient, Shore says.

While the fate of FOPers may seem bleak, there is much reason to hope, says Dr. Fred Kaplan, an orthopedist who has devoted his life to solving the mysterious genetic disorder.

Since the identification of the gene, which causes FOP, in 2006 "we are in a whole different universe" in the research, Kaplan says. "It opened up new horizons of therapy and unlocked the doors of hope."

Science Behind the Mystery

Muscles spontaneously turning into bone may sound like science fiction, but researchers now understand that it is the work of a single genetic mutation that causes the body's inflammation response to run amok.

At birth, FOP may show up as a deformity of the big toes and sometimes extra bones in the neck, but extra bone formation elsewhere usually begins in the first decade of life, Kaplan says.

FOPers feel a flare-up coming on when a particular body part becomes stiff, red, swollen, and painful -- indicating that an inflammation response is occurring. During this response, signals get crossed: instead of producing new healthy soft tissue to heal the injury, the body begins making hard tissue -- pushing out healthy muscles and ligaments in the process.

Avoiding trauma that can cause inflammation is one way to slow the progression of FOP, but for many parents, it's a tradeoff. They can protect their child temporarily but rob him of a (more) normal childhood. Or the child can jump and play like other kids, but pay the price later.

"You listen to some kids, what they remember is being a kid and being able to ride a bike and run and play and it's good for them," says Shore. "They all say they were glad they had the chance to do these things."

The average lifespan of those with FOP is the early 40s. Death is often caused by heart or lung failure after the heart has been weakened by years pumping against a hardened chest wall, Kaplan says.

Shore says future generations may benefit from increased awareness and caution -- but the real solution may be genetic-based treatments from research by Kaplan and Shore.

"Basically the mutation created a trap door in evolution that allowed something to occur that we've never seen before: the transformation of one organ into another, muscle into bone. The identification of this mutation gives us the possibility of sealing this trap door back up with appropriate therapies," Kaplan says.

"We've been developing animal models of FOP in chickens and flies and fish and mice to screen and test drugs that can seal this door back up."

FOP Community Breeds Research Advances

A large factor in making this new research possible is money raised by the International Fibrodysplasia Ossificans Progressiva Association (IFOPA), a nonprofit started in 1988 by Jeannie Peeper to "instill hope through research, education and support while searching for a cure."

Peeper was diagnosed with FOP when she was 4.

"They showed my mom and dad a couple of graphic pictures, and said 'go home and enjoy her, she's not going to live very long,'" she says.

Now 51, Peeper has exceeded expectations -- both of her own projected lifespan and of what could be done for this rare condition.

Before starting IFOPA, Peeper had not known anyone else with FOP. She started the organization as a way to bring together other sufferers, and raise funding for research.

IFOPA "lets us know that we're not alone," Kurpiel says. When she struggled emotionally with the loss of mobility in her leg at age 25, she says that the "support was tremendous."

When Peeper started IFOPA in her late twenties, she had mobility in one wrist -- virtually all her other joints were locked, including her jaw, so she says she wasn't looking for a "miracle cure" for herself.

"My desire was to make a difference for the children of future generations," Peeper says.

"Without Jeannie, we wouldn't be where we are today," Kaplan says. "Many adults with FOP say, 'What can you do for me?' Jeannie says, 'What can we do for the next generation so they can have medicine to treat this instead of a wheelchair?'"

The organization supports research by Kaplan and Shore, offers support for those with FOP who need special equipment, and hosts seminars, webinars, and international symposiums to raise awareness.

FOP research has unlocked "many of the secrets of how to create a skeleton," Kaplan says -- knowledge which might also aid treatment research for more common conditions like osteoporosis, arthritis, and ossified heart valves.

An effective treatment may still be years away, "but I think we see some lights on the distant horizon where before, there was only darkness," Kaplan says. 

By COURTNEY HUTCHISON, ABC News Medical Unit