The parents of a six-year-old boy say their son is being denied "life-saving cornflour" by chemists who they claim have replaced it with an untested drug.
GSD sufferers are unable to properly process glycogen (a type of sugar) within muscles, the liver and other cells. If untreated this results in a child's blood sugar level dropping too low for prolonged periods.
Without daily doses of cornflour, George's parents say he could slip into a coma and die.
"We have a prescription from the doctor but no chemist in Darlington will dispense it to me as it’s apparently not on their lists anymore and they won’t get money back for it," mum Sam Morrison, 43, said.
"It’s critical for George and they’re playing with his life - every child in this country is entitled to free prescriptions."
The starch in cornflour creates a slow release of energy, which stops George from suffering liver damage or falling into a coma.
Because the GSD is rare, research into it is scarce. Children inherit the condition if both parents carry the faulty gene.
Before George was born, neither his mum or dad had ever heard of GSD.
George's parents said he seemed completely healthy as a newborn and they even took him abroad for their wedding when he was just five months old.
But at eight months he began feeling very unwell and was taken to A&E.
After a series of test doctors diagnosed George with GSD.
At one point George had to be fed every hour to keep his blood sugar level - even through the night - but with the help of cornflour the family have been able to stretch this to every two or three hours.
George's family mix the flour with water and George drinks it four or five times a day. George combines his cornflour drink with a healthy diet to sustain his blood sugar and he is fed through a tube during the night.
Mrs Morrison said: "If George gets low blood sugar, he will fit and requires urgent medical help. If it’s not caught quickly enough, George will fall into a coma and he will die.
"The ongoing medication that helps his condition is uncooked cornflour – he takes 30g of cornflour several times a day and it is saving his life.
"Cornflour allows us to live a relatively normal life. It allows us to go for days out or even holidays.
"We do have to constantly watch the clock to make sure he is fed, but we can at least manage it.
"George's school is brilliant. They make sure he is fed properly and has his cornflour.
"We were getting it on prescription but the company that provided it stopped doing it and started doing something that hasn’t been tested on children under eight," the mum-of-one continued.
"I’m having to buy it in bulk from Morrisons but I don’t see why when it’s a life-threatening condition that needs this medication.
"It’s so frustrating, George is a lovely little boy and I just want to make sure he has a future."
Calling for pharmacists to reconsider the change of drug, Mrs Morrison, who works for the Department for Education, and George's self-employed plumber dad Pete, 36, are questioning why their son is being treated differently to other children who get life-saving medication via the NHS.
Mrs Morrison said: "Life with George is hard as it is an on-going battle to keep him safe – even if he picks up a tummy bug, he could end up in hospital.
"GSD is so rare that doctors don’t know anything about the disease and we have to tell them about it.
"We hit a brick wall at every corner we turn – everything that’s been done for him is because of us going to conferences, learning about it and ringing consultants to tell them.
"Nobody is coming to us with ideas or supporting us and we feel so let down, it’s exhausting.
"This is just another hurdle we have to overcome. Why can't they just make it easier for us and put it on prescription?"
The parents say it's not necessarily about the cost - his cornflour costs the family around £3 per week (£150 per year) as Morrisons cornflour is 74p for 250g - but the principle.
Mr Morrison said: "The drug they are wanting us to have costs a lot more money, and we will be willing for George to go on that when he is older. Why can't they fund the cornflour for our child when all prescriptions for children should be free?
"We are all for the new drug, but don't want him to have it while it's not been tested for children. We are completely happy with cornflour and know that it's safe."
The family are trying to raise awareness of the condition and fundraise in the hope of finding a cure in future. To donate, visit justgiving.com/curegsd.