The Herald on Sunday previously reported that Liam's case was taken to an Australasian medical conference late last year.
"A doctor from the UK saw Liam's photo and said he looked like he had Cohen syndrome," Amy said.
"He had more tests and they looked at mine and Craig's DNA and found we both carried the recessive gene for Cohen syndrome."
Amy was 12 weeks pregnant when they were told and the couple, who also have a 5-year-old daughter, were told their unborn baby had a 25 per cent chance of having the disease.
Doctors took a sample of the unborn baby's placenta and sent it to Austria for testing.
"It took seven weeks to get the results so I was 18 weeks pregnant by then and it was very stressful not knowing," Amy said.
"I look at the pain Liam goes through and I couldn't put another child though that."
Fortunately, the new baby - a girl - is not affected, but is a carrier.
The couple do not yet know if their other daughter Chloe, 5, is a carrier.
The family is focused on getting the best care for Liam, including medication for his low white blood cell count.
Dental issues, varying degrees of blindness and general ill health are also common side effects of Cohen syndrome and Liam is expected to need care all his life.
The Dyers want to attend a Cohen syndrome conference in Ohio in 2016 to meet specialists and other sufferers.
Amy says most parents celebrate big milestones, but she dreams of her son putting his arms around her for a cuddle. The only way he can express himself is by flapping his hands when he is happy and covering his ears if he is not.
"It's the little things we want to celebrate. I miss the little things like getting a kiss or a cuddle from him. I want to fill his life with happy memories because you never know what the future holds."
