For single mother Tamika Pritchard, the loss of her baby son at 17 months old came with horrifying speed.
Bowie Pritchard's death last week from a rare and incurable genetic disease has devastated his family.
"It's my worst possible nightmare. He was my whole world. My whole life was dedicated to him," said Miss Pritchard, of Gosford.
Her grief came in waves of emptiness, anger and sadness.
"It's all the emotions - all of the above," she said.
Bowie was a healthy baby and "a cheeky, happy boy", before symptoms of the disease emerged.
He lost balance and the ability to speak, before succumbing to Leigh syndrome a month after diagnosis.
A GoFundMe has been established, titled "Fundraiser for Bowie".
"I went through pregnancy pretty much on my own, but I had family support," Miss Pritchard said.
"My mum and dad were so involved as grandparents, especially with me being a single parent. They were caring and loving.
"Bowie was always happy. Everyone loved him and he loved everyone."
She said Bowie's death had been "hard on everyone", including his aunty, uncles and cousins.
Leigh syndrome is a mitochondrial disease that disrupts the body's energy production. It mainly affects the brain, nervous system and muscles.
Mitochondria produce about 90 per cent of the energy that cells need to function. The severe neurological condition affects about one in 40,000 births in Australia.
Mito Foundation chief executive Sean Murray said Leigh syndrome was "the most common type of mitochondrial disease affecting children".
He said there was "currently no cure for Leigh syndrome or any form of mitochondrial disease".
Mr Murray said almost 70 Australian babies born each year will develop a severe or life-threatening form of mitochondrial disease.
He said sustained investment was needed "across the entire research pathway: understanding the disease, developing therapies and conducting clinical trials".
Ms Pritchard researched the disease and "knew everything that was going on in Bowie's body".
"His brain wasn't getting enough energy. He was off eating and drinking. He wasn't motivated to do much," she said.
"It's crazy how quickly his life changed and how such a little life can be taken so quickly. "
She said he was a "pretty healthy baby", but his symptoms began when he was "a bit delayed in walking".
"He said lots of different words when he was turning one. That disappeared and he was just grunting and making noises," she said.
"He was losing his balance and not able to stand. He was a bit wobbly. It got really bad, so we had to go to hospital.
"They sent us to Westmead for an MRI and spinal tap. The results indicated he had Leigh syndrome."
Mr Murray said his thoughts were "with this little boy's family and everyone who loved him".
"Sharing his story takes great courage," he said.
Researchers are investigating potential therapies for Leigh syndrome, with some having reached clinical studies.
"This progress is encouraging, but Leigh syndrome has many different genetic causes. Emerging therapy may only be suitable for people with a particular diagnosis," Mr Murray said
"There are currently 15 active mitochondrial disease trials worldwide, but only four include Australian sites.
"Four therapies are approved overseas for specific types of mito, but none are approved in Australia. We must close this gap."
For support, contact Mito Foundation on 1300 977 180.
