A three-year-old boy had both his legs and most of his fingers amputated after doctors in the UK wrongly diagnosed a life-threatening infection as common childhood condition tonsillitis.
Reuben Harvey-Smith was taken to A&E at Ipswich Hospital after accidentally burning himself.
When his mum Lou took him back two days later with a fever and sore throat she was given antibiotics and told that her son had tonsillitis.
The following day he was fighting for his life.
He was later diagnosed with toxic shock syndrome, a life-threatening infection caused by bacteria entering the wound and releasing poisonous toxins into his blood.
Reuben had to have both legs amputated below the knee and also lost seven fingers after the infection took hold in July last year.
The hospital trust has admitted liability, and that amputation could have been avoided if the condition were diagnosed correctly and treated earlier.
But Ms Harvey-Smith, from Chelmondiston, near Ipswich in Suffolk, said her little "Mr Positive" refused to let it get him down.
"He came round from the operation and the first thing he did was ask for 'mummy cuddles' and his dinner," she said.
"He looked at his amputated legs and said 'poorly feet gone, get new ones.'
"He just accepts it and gets on with things. He never gets frustrated.
"I try not to waste energy getting angry because at the end of the day I've still got my son, but what I have got to do now is make sure it doesn't happen to anyone else."
Reuben's sore throat and fever had been misdiagnosed despite a recognised link between burns and toxic shock syndrome.
Ms Harvey-Smith called the burns unit at Chelsea and Westminster Hospital for a second opinion when she suspected things were still not right, and doctors immediately suspected toxic shock.
Reuben survived, but medics at St Mary's Hospital in Paddington, London were forced to amputate.
Ms Harvey-Smith, 41, later launched legal action against Ipswich Hospital NHS Trust which admitted toxic shock was a 'significant possibility' based on his symptoms at the time, and amputation could have been avoided with earlier diagnosis and treatment.
The mother, who is assistant director at the Home Office, is now raising awareness of the link between burns and toxic shock.
"It is extremely rare, but it can be life-threatening and it's just getting people to think because it's something that can progress so quickly, but if caught early can lead to a full recovery," she said.
Her lawyer, Tim Deeming, a clinical negligence specialist from Slater and Gordon, said: "Reuben has life changing injuries as the team made the wrong diagnosis in suspecting a throat infection.
"It is extremely concerning they were aware of the link between burns and toxic shock, yet didn't consider this for Reuben's case."
Ms Harvey-Smith, who has two older sons, William, 22, and Harry, 12, is now fundraising for better prosthetic legs so Reuben can get around more easily.
She said each pair cost around £6,000 and they needed to be replaced twice per year.
The NHS trust has made an interim payment of £50,000 while legal proceedings continue over a final settlement.
A spokesman for Ipswich Hospital NHS Trust said: "In an ongoing legal case the trust has admitted full liability for shortcomings in the A&E care provided to Reuben in July 2015 and have offered an unreserved apology to Reuben and his family.
"We are now working with the family to ensure that lessons are learnt from Reuben's case and further training has been provided to A&E staff on recognising the warning signs of septic shock syndrome.
"The trust is committed to ensuring that Reuben is appropriately compensated so that he has the care, prostheses and equipment that he needs throughout his life.
"Some funds have already been allocated for Reuben's immediate needs while the parties work towards settlement of the claim."