Robert Watson needs round-the-clock care, and spends up to 20 hours a day on a ventilator.

Now 27, he has been a wheelchair user since he was 10 and his need for care has increased steadily as he has grown older.

He suffers from Duchenne Muscular Dystrophy, a genetic condition which leads to muscle wasting and knows it will ultimately kill him.

But like others affected by the condition, Robert has already lived much longer than was expected when he was first diagnosed. "It used to be that most children with my condition didn't live beyond their teens, " he explains. "Nowadays, with better medical care, people are living beyond their late twenties, into their thirties – a lot of us are living into adulthood."

Medical advances are good news for those affected by this distressing and debilitating condition. Living longer has enabled Robert to get a degree – he achieved a 2.1 honours degree in computer games technologies at the University of the West of Scotland. But it also now poses a problem for Robert and his family.

For 15 years, as a child with a life-shortening illness, he has benefited from the services of the Children's Hospice Association Scotland (CHAS), which runs two hospices, in Kinross and Balloch.

These provide end-of-life care for children with terminal illnesses and respite care for the families of young people with longer- term conditions.

Robert has been going there for four weekends a year, and an extended stay in the summer since he was 12. "It lets me socialise with other people who have a similar condition, play computer games, and watch films," he explains. "It also gives my parents a break. I need constant care as my breathing gets worse with ventilators and heart medication. I can't be left unattended for any period of time and I have to be looked after 365 days a year for 24 hours a day, so those breaks are important for all of us. With my situation it is not healthy for us to be with each other all the time with no break."

However this week, Robert's parents, Robert senior and Eunice, and around 100 other families across Scotland received a letter telling them the chance to benefit from CHAS services is being withdrawn.

The charity says that while medical knowledge means more children are living into adulthood with serious conditions, that poses it with a problem. For the first time it has decided to put an upper age limit on those who can use its services.

Families have been told transition workers will help them find alternative adult services, but CHAS will gradually withdraw services from young people of 21 and over during the next three years.

Robert admits that sometimes if he attends Rachel House, in Kinross, and there are no young people his own age staying it can be unsatisfactory. "I understand it isn't their fault," he says of the change being imposed by CHAS.

But he has looked for alternatives and says the adult services currently on offer are far from appropriate.

"I've been looking on my own but the problem is there is nowhere else. There are no services for people of our age group.

"There is nothing in between CHAS and hospices for older adults in their fifties and sixties who are mainly suffering from cancer.

"We're all very concerned because there doesn't seem to be anywhere else for us to move on to."

Some of the existing respite care providers charge hundreds or thousands of pounds for a stay, he adds, while hospices for older adults often don't provide respite breaks, just end-of-life care.

"The Scottish Government should be doing more to support us," he adds. "CHAS have said they won't just abandon us, but it is a concern."

His mother is less sanguine. "I don't know what we're going to do," she says. "What's the point of having transition workers, when there is nothing for them to transition to? There is nothing out there for them.

"This was introduced with no consultation with the parents or the young people themselves."

Eunice Watson claims that while Robert is on the charity's young adult council, members were told a decision had been reached about an age limit, but given no input into the decision or what the age limit should be.

"There is a lot of anger about this among families," she adds. "When the charity was set up, the pledge to parents was that it would be there for them from the point of diagnosis to the point of death, and beyond. That was what the parents who set up the hospices said and that is all being ignored. Parents are being pushed aside by the professionals.

"It would be different if there was something out there for them, but there is not."

Asked whether there will be a campaign on behalf of parents to overturn the decision, Mrs Watson is pessimistic. "Some parents have been caring for 20-odd years and now they are going to be left high and dry. We are done, we are exhausted. We haven't the energy or the fight in us to do it any more," she says.

Maria McGill, chief executive of CHAS, is not unsympathetic to the anger felt by some parents, and says the decision the charity has taken has been reached slowly and with regret.

"We've always been there with these young people and when it started, CHAS did say we'll be with you as long as you need or want," she says. "That message is changing."

However other hospices in England and Wales have age limits and the charity has had to consider how appropriate it is for a young person in their twenties to be in an environment where young children – some just infants – are dying, she argues.

"When you talk to people in this group some will admit that what we provide is not really what they want or need," she says, pointing out that young adults using the centre can expect to watch Disney films and take part in other activities not suited for their age.

Regulatory agencies have also raised eyebrows at adults regularly using the services of a residential facility for children, she adds.

But Ms McGill insists CHAS is keen to provoke a debate about this issue and is not turning its back on the families affected.

"There is nowhere we can instantly put people and that's why we have transition workers.

"We have had a relationship with these families sometimes for 16 years. This is a forgotten group in Scotland, and they talk about falling off a cliff. We are failing our young people and we are not the society we claim to be if we don't address this."

CHAS will work with civil servants, politicians, hospices and other groups to try to provide alternative services. Some other charities already see the value of expanding their role to provide suitable services, she adds. "I am telling families that if after three years we haven't met their needs somewhere else, I will consider we have failed."