Acting quickly, she took him to the GP, which led to an MRI and a series of further tests. Eventually, Kye was diagnosed with Leigh's disease, a rare and serious mitochondrial condition.
Kye is now two and is the only known case in Australia with the ABAT gene.
"We just never expected to get the diagnosis of Leigh's syndrome. It was a huge shock," Ms Gray said.
"He doesn't have that head control. His eyes shake a lot but he's got abnormal brain activity. Given how rare the condition is, they just don't know a lot."
That has since changed, following a breakthrough genomic blood test developed by researchers from the University of Melbourne and Murdoch Children's Research Institute.
The breakthrough test allows parents to screen not only for the gene linked to Leigh's disease but also for thousands of others.
"They've been able to confirm the genetics behind it, which has enabled me to meet other families with this condition. (There are) about 15 reported cases of the ABAT variant worldwide," Ms Gray said.
The test has provided clarity for Ms Gray and her family.
"At least we have been able to confirm the gene and that's really important. We want more children one day, but could never go through this again," she said.
"Having this genetic diagnosis means we are able to test in any future pregnancies."
The research, published in Genome Medicine on Thursday, has been labelled revolutionary as it can help avoid expensive and invasive procedures and allows doctors to start treatment sooner.
Doctors currently use genome sequencing to diagnosis of rare diseases, although it only works in about half of the case.
This test can rapidly detect abnormalities in up to 50 per cent of all known rare genetic diseases in a matter of days by analysing the pathogenicity of thousands of gene mutations at once.
"We've been working on this testing for about 10 years ... we believe we've effectively turned the corner from this being a research test into something that will be able to be offered in a clinical diagnostic lab," Murdoch Children's Research Institute David Thorburn said.
"(It) will enable diagnosis of potentially hundreds of patients a year in Australia."
Biomedical scientist David Stroud, from the University of Melbourne, described the test as a breakthrough as it can test for thousands of genetic proteins at once.
"What is unique in our test is that it can test for all the proteins in a particular sample. This equates for about half of the known genes that can cause rare diseases," he said.
If the test can provide clinical diagnoses for even half of the 50 per cent of patients who don't get a diagnosis through genome sequencing, that's a significant outcome.
"It means those patients don't have to undergo unnecessary and invasive testing such as muscle biopsies, which for a baby requires general anaesthetic and that doesn't come without risks," Professor Stroud said.
Researchers are in the process of recruiting 300 patients with a range of different genetic disorders to participate in a study to investigate the broad utility of their diagnostic test.
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