When five-year-old Charlie Parkes was in the womb, a scan revealed a problem with his brain. He spent his first two years of life in hospital having tests. His parents were desperate for answers - but they never came.
"We have lots of little pieces of a puzzle, but they don't quite fit together. We haven't completed the picture yet," says his mother Laura.
Charlie is one of about 6,000 children born every year with a genetic condition so rare that doctors can't identify it and instead classify it as a Swan (Syndrome Without a Name).
Each case is thought to be one of a kind. Without a diagnosis, families can feel isolated and face a battle for treatment, Mrs Parkes said.
Alongside sensory processing issues, hypermobility, allergies, a weakened immune system, digestive and bowel problems, anxiety and attachment disorder, Charlie is on the autism pathway and doctors are looking into a possible connective tissue condition.
"We were suddenly thrust into this world of tube feeding and medicine schedules. We felt very alone. At one point we were under 20 different doctors for different issues.
"Not having a diagnosis very often means you don't tick boxes. We've had to fight for everything, every service, every bit of extra support and equipment."
Charlie, who lives in Corby, Northamptonshire, did not babble or sit up like other babies. But florist Mrs Parkes and her husband Steve were not worried about him missing milestones - they were too busy keeping him alive.
"It was terrifying how quickly he could deteriorate as a baby, suddenly we'd be searching for the oxygen and calling the ambulance," she said.
The tractor-loving boy seems like any other young child on the surface, but that is part of the problem, according to his mother.
"We've been made to feel like it was our fault, even by medical professionals.
"We've lost family and friends and have been accused of making up Charlie's problems because we don't have a diagnosis people can just 'Google'.
"I particularly have struggled with my mental health as a result."
Charlie attends a mainstream school and Mrs Parkes said she was so proud of her "unbelievably cheeky" little boy, who has recently learnt to hold a pencil.
"We were told he might not walk or talk and it's mind-blowing how far he has come.
"We're always learning how we can help him calm down, whether that's having multiple baths as he finds water really relaxing or letting him outside to dig in the mud or his sandpit."
Charlie's family, including his seven-year-old sister Chloe, who is "fiercely protective" of her little brother, have found support from the Swan UK organisation.
It holds an awareness day on the last Friday of April each year, calling it Undiagnosed Children's Day.
Lauren Roberts, national coordinator for Swan UK, said it was a chance for these families, who were often "invisible" and "living in a limbo land", to come together.
"Although most families understand a diagnosis is not a magic wand, they live in hope that it might provide answers and relieve some of their fears - fears about what the future holds for their child, fears about whether future children might be affected and fear that it was something they did," she said.
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If people doubt Charlie is ill, Mrs Parkes said she now directed them to the Swan UK website, meaning she could prove he was poorly and that she was not making it up.
Charlie will probably never get a formal diagnosis, but the family has started to accept that. As for the future, Mrs Parkes hopes her son can stay as "happy and resilient" as he is and learn to "embrace his quirks."
"He has smashed every goal and expectation anyone has ever had about him, he has ripped up the medical textbook and rewritten his own, like many of our Swans.
"He has been through more tests, procedures and surgeries in his short life than anyone should ever have to, but all with a cheeky smile and has made many people giggle along the way."