Owen Howkins, eight, has a rare genetic disorder that made him withdrawn and very nervous in social situations.It had a huge impact on his life because it made it very difficult for him to make friends.
But one day, the schoolboy's dad, Will, brought home a dog from a rescue centre because the family wanted a pet – and it has changed Owen's life.
Speaking about the moment he met Anatolian shepherd dog Haatchi, Owen - who is known to his family as Little B - told ITV's This Morning: "He put his head on my lap and that's how we became best friends forever.
"He's my best friend in the whole world."
Owen and Haatchi are now the stars of a new book – called Haatchi and Little B – which tells the story of how the pair have become firm friends.
Owen said: "I used to be scared of strangers and I used to put head down before Haatchi came. But when Haatchi came I wasn't scared.
"He changed how I felt about being in a wheelchair. He's special because he changed my life."
Dad Will said that when he and Owen's step-mother, Colleen Drummond, went to get the dog they did not know it would have such a strong impact on their boy.
He said: "About three weeks after we brought Haatchi home Owen wanted to take him for a walk in his wheelchair.
"That day he was still hiding in his wheelchair. But he got more confident when people were complimenting his dog and then he realised that people were looking at Haatchi more than him in his wheelchair."
Haatchi himself had a difficult start in life, suffering horrific injuries when he was tied to a railway line and hit by a train. He was found days later, cowering, with a mangled tail and back leg.
By the time he was taken to a vet's surgery, nothing could be done to save his leg and tail and both had to be amputated.
Haatchi's future looked bleak as the RSPCA and UK German Shepherd Rescue Centre struggled to find him new home.
But he was eventually adopted by father Will and his wife Colleen who read about the animal's plight on Facebook.
Colleen said: "As soon as they met, the effect Haatchi had on Owen was incredible."
Owen's condition requires regular hospital treatment but the simple joy of being around the 'energetic puppy' makes it easier for him to cope.
Their relationship led to Haatchi being honoured with a top award at Crufts last year, winning first place in the Friends for Life category at the annual dog show at the Birmingham NEC.