Twin sisters Zoe Buxton and Lucy Fretwell, 26, have a one-in-two-million genetic condition that is slowly turning them to stone.
The pair from Ballymena, Northern Ireland, are one of just three twins worldwide known to have a condition, called fibrodysplasia ossificans progressiva (FOP), which causes their muscle and tendons to be replaced by bone.
Although their future is uncertain, both women are determined to remain positive and are even considering having children despite the risk their condition may be passed on.
Ms Buxton said: 'We refuse to let our condition stop us from living life to the full.'
Ms Fretwell added: 'It is difficult to stay positive, but it helps to have someone else going through the same thing as you.'
Twin sisters have a one-in-two-million genetic condition that is slowly turning them to stone
Zoe Buxton and Lucy Fretwell, now 26, have fibrodysplasia ossificans progressiva (FOP)
FOP causes bone to replace muscles and tendons (Ms Buxton pictured in the wheelchair)
Fibrodysplasia ossificans progressiva (FOP) is a very rare inherited disorder that causes bone to appear in tendons, ligaments and muscle.
At birth, most sufferers have shortened big toes.
Any part of the body can be affected by FOP.
It also causes swelling, limited movement and difficulty eating or speaking if the jaw is affected.
Complete immobilisation can occur.
There is no cure.
Treatment focuses on relieving pay and aiding mobility.
Sufferers should avoid activities that may cause injury.
Both found love
When Ms Buxton, a fashion blogger, was 17 she met her now-husband Mike Buxton, 29, a gasman, online.
She said: 'Mike's a selfless person, and he always puts me first.
'He understands that I get frustrated when it takes me an hour to get dressed in the morning, and he never complains.'
The couple married in 2012 and Ms Buxton chose to walk down the aisle instead of using her wheelchair, which she sometimes needs for long trips away from home.
She said: 'Just because I have a disability, it didn't mean I couldn't enjoy the happiest day of my life.
'Mike and I would love to start a family, but there is a 50/50 chance that I'd pass on FOP to my child.
'He would rather me be alive and healthy than have an ill wife and child.'
Ms Fretwell, who looks after her older sister's children, met her now-fiancé Michael Smyth, 27, a teacher, in 2015, and the couple got engaged a year later.
She said: 'When Michael proposed while we were on holiday last year, I was ecstatic.
'I'd love kids one day, but it's not an option at the moment.
'We'd definitely consider adoption after we get married.'
Although their future is uncertain, both are determined to remain positive (Ms Buxton left)