Two-year-old Jessie Plumpton has Jeunes Thoracic Dystrophy, and her rib cage has not properly developed, leaving her lungs under pressure.
The toddler endured a seven-hour operation at London's Great Ormond Street hospital before being transferred to Alder Hey Children's hospital in Liverpool to recover.
In the pioneering surgery, a titanium bar was fitted vertically down the middle of both halves of Jessie's rib cage to open her ribs in both directions and create more space in the cavity.
Her mum Jane said: "The chest expansion was very traumatic because it was a life or death operation. She could have died in surgery."
Jessie, who is from Runcorn in Cheshire, was diagnosed with Jeunes - which affects around one in 130, 000 youngsters - when she was just two months old. She has an older half-sister Jennie Leigh, 9, who is not affected.
The genetic conditions puts sufferers at risk of respiratory infections and possible kidney failure.
Jessie is still attached to a ventilator to assist her breathing, but her mum says she is doing well:
"She needs ventilation wherever she goes because her lungs are under-sized, but developmentally she's bright as a button.
"She is a little fighter. It's a dream come true having Jessie. Doctors are surprised she has made it this far but I've always had faith in her. She is a miracle. Nurses say Jessie is a different baby when I walk in the door. Her face lights up. It's brilliant."
The little girl will need further as she grows to further expand her chest.
Her mum hopes to have her back home in time for Easter and says she is "really proud "of her:
"She is unstoppable. It's the best feeling in the world to have her in your life."
What a fantastic story! Let's hope Jessie is home in time for the Easter bunny!