Scientists have discovered why type 1 diabetes is more severe and aggressive when it develops in young children.
Type 1 is caused by the immune system attacking cells in the pancreas that control blood sugar levels.
The research team showed the pancreas was still developing in childhood, particularly under the age of seven, making it far more vulnerable to damage.
They say newly developed drugs could buy patients time for the pancreas to mature, delaying the disease.
Type 1 diabetes affects around 400,000 people in the UK.
Gracie, age eight from Merseyside, became suddenly ill on Halloween in 2018. It started as a slight cold, but rapidly escalated.
"She went from being a very happy one-year-old, who would go to nursery and dance and sing, to almost dying in less than 48 hours," says dad Gareth.
"The diagnosis remains the worst part of our life. Suddenly everything we took for granted was 10-20 times harder," he says.
The Nye family had to adapt quickly - keeping on top of everything Gracie had to eat or drink, checking blood sugar levels and giving the hormone insulin to tell her body to absorb the sugar in her blood.
Gracie now has a glucose monitor and an insulin pump and is "bossing diabetes", says her dad.
"Gracie's a superstar," he adds.
But why children diagnosed young like Gracie, especially those under the age of seven, have a more aggressive disease than those diagnosed in their teenage years or later, has remained a mystery.
The study, published in the journal Science Advances, shows it is down to the development of the beta cells living in the pancreas.
These are the cells that release the hormone insulin when sugar levels rise in the blood after we eat.
Researchers at the University of Exeter studied pancreas samples from 250 donors, allowing them to see how the beta cells formed normally as people got older, and in type 1 diabetes.
The research was part of the Type 1 Diabetes Grand Challenge organised by the Steve Morgan Foundation, Diabetes UK, and Breakthrough T1D.
Rachel Connor, director of research partnerships at Breakthrough T1D, said: "This study gives us a missing piece of the puzzle, explaining why type 1 diabetes progresses so much faster in children than in adults."
Dr Elizabeth Robertson, director of research and clinical at Diabetes UK, said: "Uncovering why type 1 diabetes is so aggressive in young children opens the door to developing new immunotherapies aimed at slowing or stopping the immune attack, potentially giving children more precious years without insulin therapy and, one day, preventing the need for it entirely."