A boy has been told his "next seizure could be his last" - after being diagnosed with one of the world’s rarest deadly diseases."

William Howard, nine, was told by doctors his initial symptom, a twitch in his right leg, could be down to stress from playing Minecraft.

But after "endless" medical investigations, an MRI confirmed he has mitochondrial disease - which means his cells won’t work correctly. "

He is one of 10 people in the world who have his particular variation - DNML-1.

His parents, Simon, 45, and Mihaela, 43, say he went from a normal, healthy little boy to paralysed by seizures, seemingly overnight.

And they’re having to take each day as it comes - never knowing whether it could be their last with William.

Mihaela, an ex-nurse from Swindon, Wiltshire, said: "Doctors have told us to prepare for the worst - one more seizure could be it for William. We’re terrified - but he’s a fighter."

"It’s a reason to get out of bed in the morning, because it’s one more day with William. "

"I’ll check on him and see he’s sleeping in his bed - and in that moment I think, we’ve got at least one more day together."

William was first driven to hospital by his family on May 21, 2020, when his parents noticed his right leg "dropping" when he tried to walk."

Simon called 111 - and was told to take him to the GP the next day - but drove him straight to hospital when William was struggling to walk to the toilet.

Simon, a chef manager, said: "William was going around like normal - but suddenly his leg would give way and he’d fall over."

"He’d laugh it off, go around, and it’d happen again."

"We thought he was joking about it - but then it became more constant. "

"So we drove him to Great Western, where he was told initially he might’ve broken his coccyx."

"They recommended we transfer him to John Radcliffe for further tests, so we drove him." "

At first, doctors feared it may be Covid - but after a test came back negative, told the couple it may be down to stress.

"William was watching silly things about Minecraft on YouTube," Simon added. "And he was getting worked up. "

"So we thought this must be the reason. "

"He literally had his game thrown in the bin while he was with the doctor, but then the weakness began to affect his upper body."

Doctors admitted William for further tests but he had a full-body tonic-clonic seizure - uncontrollable stiffening and twitching of the muscles.

He was put in an induced coma and had more tests.

Simon added: "While he was in the coma, one of the MRIs flagged up mitochondrial disease - which no-one really knew about."

Mihaela, Simon and William’s six-year-old sister, Sofia, were each DNA tested for the typically hereditary disease - but none of them had the gene.

It was concluded William had late-onset mitochondrial disease, which he’d "grown" from his own body. "

Only nine others in the world have it - each with different symptoms.

There are no treatments and William wasn’t given an official prognosis - but doctors say every seizure may be his last, his parents say.

"I needed a lot of time to cry and calm down," Mihaela added. "I needed to be by myself."

"I couldn’t believe it."

After two months in the coma, William woke up in July 2020.

Since, he has lost the ability to eat and drink - and he relies on a nasogastric (NG) tube for nutrition.

He is registered blind, and has been told the disease is slowly shutting down each of his vital organs.

On December 7 2023, he went into his second coma after suffering another massive seizure, lasting 56 minutes and seven seconds.

Simon said: "He got told by the doctor that this might be it - but he was only in it for a week."

Mihaela added: "We prepared for the worst - the day of his big seizure, he also had 13 other seizures."

"The doctor was really shocked he came around after only a week - and William was even able to make it out by Christmas!"

The couple say they were "grateful" to have been able to make memories with William over the Christmas period - despite making do with no tree, decorations or Christmas dinner. "

"We had nothing," Mihaela said. "But it was amazing to be there."

"To go through what we went through, and to see your child home - nothing else matters."

"Nothing can change that happiness."