Up until the age of five, Greg Olsen was healthy, energetic and tall for his age.
But, over the next four years, Greg's parents were baffled as to why he hardly grew, lost a considerable amount of weight, was always feeling sick and didn't eat much.
Between 2008 and 2010, Greg grew only five centimetres, felt lethargic all the time and had become anaemic.
"We saw several doctors throughout that time," says mum Michelle. "There were different theories about what was making him sick but nothing fixed the problem. At one point, he was even referred to a psychologist.
"We thought he had cancer - he had such dark eyes and skinny legs."
Dad Steve says it was frustrating to see their once-healthy son fading away with no explanation.
Finally, in September 2010, Greg was diagnosed with coeliac disease after a paediatrician ordered a battery of blood tests, with the diagnosis confirmed by a paediatric gastroenterologist at Randwick Children's Hospital.
Steve and Michelle were relieved to finally have an answer.
"We were shocked because this was supposed to be a genetic disease and neither Steve nor I knew of any family member with coeliac," Michelle says.
Three years after the diagnosis and now aged 11, Greg has put on 20 kilograms and grown 15 centimetres.
"All day every day I used to feel sick, I'd have constant headaches and tummy aches," Greg says of what life used to be like.
"I just thought that was normal."
Greg's body initially struggled to get used to the rapid weight gain after starting a gluten-free diet but the Flinders student's energy continues to increase and he now enjoys playing cricket and soccer. So much so that he would like to be a national cricketer one day.
"If the cricket doesn't work out maybe [PC] game design," he adds.
Michelle shakes her head as she recalls serving Weet-Bix for breakfast and making Vegemite sandwiches for school. What she thought were healthy food options were actually making her son sick.
"We felt so embarrassed; looking at the photos now we realise how sick he looked," Steve adds.
Doctors have said that although Greg is now healthy on a gluten-free diet, he will never make up the years of lost growth.
Steve hopes this story of their battle to get Greg diagnosed will help others who may be unknowingly living with the condition. He suggests compulsory blood testing for children, to help diagnose conditions such as coeliac disease at a young age.
The family, including Greg's 10-year-old sister Cassie, has comfortably adjusted to eating gluten-free.
Greg says his favourite food these days is curried sausages. Gluten-free breads aren't so nice but the cakes are good, he says.
With the progress he has made, Greg now only needs yearly check-ups. Formerly, he needed twice-yearly tests.