Corey Halliday looks like an ordinary 13-year-old.
But behind his cheeky grin is an extraordinary teenager, born with a one-in-a-million illness that threatens to cut him off from the world.
Corey is one of a handful of Australians diagnosed with Kostmann's Syndrome, a severe congenital disease that means his body cannot fight bacterial infection.
Paper cuts, colds and mosquito bites have all put Corey in hospital - he has been admitted about 80 times - because he does not produce the white blood cells needed to battle illness.
"Basically, Corey should be a boy in a bubble," said his mother, Amanda Halliday. "He should not be allowed to go outside, mix with other kids or go to school. We can't wrap Corey up in cotton wool - and we haven't - because it would be no life for him."
Corey has survived life-threatening conditions including pneumonia, blood infections and a lung abscess "the size of his lung.”
But his biggest battle lies ahead.
The teenager, from Ferntree Gully, Australia, urgently needs a bone marrow transplant to prevent the imminent onset of leukemia - and potentially cure him.
Recent check-ups showed Corey has developed myelodysplasia, a precursor to the blood disease.
"If we don't do the transplant, he's going to get leukemia," said Dr. Peter Downie from the Royal Children's Hospital. "We've got to do it within the next three or four months. To leave it any longer is risky."
However the risks of going ahead with a bone marrow transplant - a procedure similar to a blood transfusion - are equal to doing nothing.