Little Millie Barker is holding her stuffed monkey in both arms, twirling and whirling round the room to the beat of the music.

East Anglian Daily Times: Three-year-old Millie BarkerThree-year-old Millie Barker

She throws back her head of golden curls and lets out an almighty shriek of delight.

East Anglian Daily Times: Lumps appeared on Millie's back, sparking concerns she may have cancerLumps appeared on Millie's back, sparking concerns she may have cancer

To anyone watching, she’s the very picture of a normal, happy, fun-loving three-year-old.

East Anglian Daily Times: Millie Barker's toes turn in - a key indicator of FOPMillie Barker's toes turn in - a key indicator of FOP

But to her mother Lorraine Turner, who sits just an arm’s length away ready to catch her at any moment, she is also a child who needs protecting more than most.

Just six months ago Millie was diagnosed with Fibrodysplasia Ossificans Progressiva (FOP) – a condition so rare it affects one in two million people with only 700 confirmed cases worldwide, 40 in the UK.

FOP causes bone to form in muscles and other connective tissues, eventually forming a second skeleton that restricts movement completely. And every fall, bump or bruise Millie could make it worse.

“I watch her with my heart in my mouth,” says Lorraine, who lives in Framlingham with Millie and son Ethan, 7, and partner Chris.

“I want her to have as normal a childhood as possible but at the same time I want to wrap her up in cotton wool.”

Getting the balance right is difficult for the family.

Millie needs to avoid activities that could cause her injury such as bouncing on a trampoline, play fighting with her brother or running.

She can’t even walk too far without suffering muscle fatigue which can cause a flare.

But she does have plenty of friends, enjoys making models out of Playdough, watching films, feeding her new pet fish Sparky and Kipper and dancing to her portable stereo.

And she is also desperately looking forward to starting in the reception class of her local primary school in September.

“She’s a cheeky, giggling, happy, bright girl,” says Lorraine, who works part-time selling advertising space.

“My biggest fear is having to explain her medical condition to her as she gets older. She knows she has to take care of her body and that she needs to be careful but she’s pretty oblivious to the seriousness of it all.

“She probably just thinks I worry more than her friends’ parents do.”

She watches as Millie climbs unsteadily up on to a chair at the kitchen table, catches her eye and shakes her head. Millie blows a raspberry and grins.

“If I had £1 for every time I’ve told her to slow down, to take care, to walk or stop climbing I would be a millionaire,” says Lorraine, who sweeps a giggling Millie up into her arms and smothers her in kisses.

Millie was born at Ipswich Hospital in July 2010 after a normal pregnancy.

At her birth, doctors noticed her big toes looked like bunions, were significantly shorter than the others and turned inwards – a key sign of FOP – but, because the condition is so rare, no diagnosis was made.

It was not until last year, following a spell of hearing trouble and an operation for grommets, that they realised something was dreadfully wrong.

“A month after the operation she started to get prominent lumps in her neck,” says Lorraine, who clasps her hands together in her lap.

“They were large and solid and she was complaining of some pain and discomfort. Then she developed a huge lump on her back.”

After an ultrasound which proved inconclusive, she was admitted to hospital and doctors ordered a biopsy, telling Lorraine they feared she might have cancer – a cluster of tumours.

But then a consultant paediatritian who happened to be on call, said she recognised the symptoms as FOP and the procedure was called off.

Millie was then referred to Great Ormond Street Hospital, in London, where a clinical diagnosis was confirmed.

“It was pure chance that the doctor who was on duty had come across FOP before,” says Lorraine. “Children can go years without explanation for the symptoms and biopsies and surgeries can make the problem significantly worse.

“It took a long while for her diagnosis to properly sink in.”

Attempts to surgically remove any bone growths result in more robust bone growth in patients with FOP.

Life expectancy for this condition is 40, although Lorraine is adamant that long-term prognosis is not something she wishes to dwell on.

“I shed my tears and I have moments of terrible sadness but I also know my daughter is a tough kid,” she says. “All I can focus on now is raising awareness of her condition and raising money to help find a cure.”

To donate money to Millie’s fund to help the research team find a cure please visit her Virgin Giving Page - http://uk.virginmoneygiving.com/team/MillieFOP.