The disorder, which has been identified for the first time, has made Mackenzie Fox-Byrne unable to speak for life. He has learning difficulties and has no sense of danger as a result of the gene mutation, the Daily Mail reported.
At the moment, he has the mental age of a two-year-old.
Mackenzie's mother, Sharon, first noticed something was wrong with him, when he was just three months old. He was unable to lift his head from his cot, found it difficult to hold down food and had trouble sleeping.
Doctors at Wessex Clinical Genetics Service in Southampton University Hospital found that he had a triplication of a small region on the long arm on his X-chromosome.
Karen Temple, professor of medical genetics at Wessex confirmed Mackenzie was a totally unique case.
""In every cell, Mackenzie has got an extra part of a chromosome. In layman's terms if you think of some beads as part of a chromosome, he has got two extra parts."
In this case there is a rearranging of the chromosomes that is unique to him. We have to learn what we can from the little boy as he grows up," Temple said.
"This little boy has had this chromosome problem since he was conceived, we can learn from how he is now and that helps us to predict his future," she said.
Sharon (40), was informed over telephone about her son's condition by the Wessex authorities as "they had found something rare that no one else has."
"Unfortunately, that was all they could tell me. They couldn't tell me how he is going to progress or whether he might fall ill in the future," Sharon said.
"It would be fantastic to actually know what he had because at the moment we don't know what his life expectancy will be or whether he might become ill in the future."
"We do know he can never be allowed to have children as he would pass his genes on to them and we wouldn't know what their condition might turn out to be," she said.
"My hope for him is that someday he will get better and be able to live a normal life like other children, but I know the likelihood of that happening is very small."