Battling Leeds twins have taken on potentially fatal meningitis THREE times between them and come out smiling.
Now immunology experts are investigating why Helen and Georgia Tomlinson are so susceptible to the lethal brain bug.
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Mum Sarah said: "It's really unusual. There's a problem with their immune system but nobody knows why."
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Their mum is also warning other parents about the disease – especially the mistaken belief that symptoms always include a rash.
Helen, of Yeadon, was 14 months old when she became listless and was sick, but alarm bells rang when Mrs Tomlinson noticed the fontanelle – the soft spot on the top of her head – was bulging.
"Normally at her age it would have been closed but it was only when I felt that, I thought 'that's not right'," she said.
"I never thought for one minute about meningitis."
Because Helen did not have a rash, she had no idea it could be meningitis even though the rash, a sign of blood poisoning, does not always appear.
At hospital, doctors found she had pneumococcal meningitis.
"When they said it was meningitis, I was shocked," Mrs Tomlinson, 39, said.
"They gave her intravenous antibiotics and fluids. We had to just watch and wait. It was horrible and seemed like such a long time."
After a few days Helen started to recover and though there were fears it might have left her with health problems, she seems to be unaffected.
Seven months later, Georgia suddenly became ill. However Mrs Tomlinson said she and her husband Paul didn't suspect meningitis, but as she had a high temperature they took her to hospital.
They were stunned when Georgia was diagnosed with the bug too.
Georgia also made a good recovery and both twins were put on antibiotics.
But the illness struck again 18 months later, when Georgia was nearly four. This time she was treated for meningitis straight away and it was less severe.
The twins, now eight, are doing well and are active and chatty.
They are still undergoing tests with an immunologist at Leeds General Infirmary to investigate any genetic reasons why they kept picking it up,
And Mrs Tomlinson is backing the Meningitis Trust's Don't Wait For a Rash campaign to let people know a rash isn't always present with meningitis.
"I am asking everyone to learn the signs and symptoms of meningitis and don't just rely on the rash appearing, as in our case it didn't appear. Trust your instincts and get medical help immediately," the mental health nurse said.
"When I look back they had every other symptom apart from a rash."
Meningitis can start with flu-like symptoms.
* For details, call the Meningitis Trust 24-hour helpline on 0800 028 18 28, download the free iPhone app or visit: www.meningitis-trust.org