Michael Beynon was warned by doctors he may need a wheelchair for the rest of his life.
But this weekend, the 25-year-old becomes the first person with Down's Syndrome from Wales to run the London Marathon - held virtually this year.
He also has a visual impairment and muscle condition, hypertonia - but wasn't going to let that stop him.
"I've had a dream of running a marathon," Michael tells Radio 1 Newsbeat.
He ran in aid of learning disability charity Mencap, to help change attitudes.
"I'd like to give something back so they can continue supporting people like me. People with a learning disability".
As you can imagine, running a marathon takes a lot of preparation. And lockdown gave Michael the chance to do that.
"I've been doing lots of virtual challenges during lockdown to stay fit and motivated."
He's been doing practice races which at times "has been good, sometimes hard".
In this year's virtual marathon, runners have 23 hours 59 minutes and 59 seconds to complete the 26.2 miles - either by running, walking or jogging.
And it's not the first time Michael's attempted something sporty - in fact, he's got a stellar track record.
He's represented Wales and Great Britain in the Special Olympics which has seen him win over 60 medals across different events, including shot-put, long jump and track events such as 100m and 200m.
Michael says he's inspired by his family - and running giant Mo Farah.
And that support has meant he's not let his learning disability hold him back.
"If you have a dream, aim high," he says.
Erica Walker, Michael's mum says he's "he's always been very inspirational and a determined young man".
Nothing ever seems to faze him and he "puts 150% into everything he does".
"He's stubborn, determined and always has a lot of reserve in him to try and be committed at whatever he does."
'Determined to live'
Erica says from the day he came out of an incubator at six months, that was "the turning point".
"He was determined to live."
A testament to his determination is his performance at the Special Olympics skiing competition this year.
"With his vision impairment, we didn't even think he'd come down the slope. But he's blown me away and running a marathon will do that even more."
Erika will be running as Michael's support runner - and she's excited even if it's "been a while" since she's last run a marathon.
"But it's nice doing it alongside him and letting him achieve what he wants to."