Parents know this disorder will end their kids' lives
Kelly and Rory McElligott live with the insurmountable pain of knowing that two of their three children will not survive past childhood.
Maggie, 6, and Billy, 5, will be robbed of the ability to play, laugh, talk and move freely as the degenerative Tay-Sachs Syndrome takes over their bodies.
Bright, bubbly Maggie was diagnosed with unrelated global delays as a toddler meaning she was always slower to speak and walk than her peers.
But Maggie was talking and doing ballets lessons when her parents became concerned her abilities had started to decline.
She underwent a myriad of tests and procedures and was eventually diagnosed with the incurable and always fatal Juvenile Tay-Sachs syndrome.
"At that point it was a complete devastation and a combination of really complex emotions and grief," Mrs McElligott said.
"You don't really know how to process it until you are dealt those cards."
Tay-Sachs is a rare genetic disorder caused by a mutation in the hexa gene which strips the body of its ability to break down a substance called GM2 ganglioside.
The substance builds up in the nerve cells of the brain and spinal cord leading to seizures and eventual loss of all cognitive function and paralysis.
Mrs McElligott said one of the most difficult aspects of the diagnosis was that there is no known treatment or cure for the disease.
Sufferers are expected to live to late childhood, with oldest known survivor of the disease living to just 15.
After suffering multiple seizures Maggie was stripped of her ability talk and walk and is now wheelchair dependent.
"The most heartbreaking thing is that her understanding of the world has gone backwards," Mrs McElligott said.
"She was really bright, bubbly little girl."
Both Billy and Alice had a 25 per cent chance of inheriting the Tay-Sachs mutation.
Heartbreakingly, the McElligott's learned Billy too had the fatal illness.
Luckily, Alice does not.
"It some ways it was so much worse," Mrs Elligott said of Billy's diagnosis.
"You kind of cope with having that news that one of your children will die, the news that you would lose a second child was different."
So far, Billy's regression has been much slower than Maggie's - at age five he is verbal, mobile and loves interacting the girls.
But Mrs McElligott can see a growing sense of frustration building in Billy as he becomes more clumsy and forgets things quickly.
"Maggie always had a delay she never comprehended what was happening and protected her," Mrs McElligott said.
Billy does not have that same protection.
But the young parents are constantly surprised by the bond and love the siblings, who are "the best of friends", have for each other.
The family hopes sharing their story will raise awareness of incurable genetic diseases so other families do not have to experience the feeling of isolation and helplessness that they felt.
"In those early says and months we felt so, so lonely … we want people to know these disease like Tay-Sachs are real and they are more common that you think," Mrs McElligott said.
The family established a GoFundMe page to buy a car to accommodate Maggie's wheelchair so they can make their most of their time as a family five.
To support the family visit Wheels for Maggie and Billy's wheels at gofundme.com.
Originally published as Geelong couple living parents' worst nightmare