The biopsies and blood tests completed, and Zainab Mughal's rare blood mutation explained, her parents came to grips with the sudden complication in their daughter's cancer fight. In order for the 2-year-old to survive, it would take something they had absolutely no control over: The kindness of strangers.

Zainab, who lives in Florida, was diagnosed in October with a neuroblastoma, an aggressive cancer that usually occurs in children. Doctors said the tumour had been growing inside Zainab's abdomen for nearly half of her life. Fighting it would require two bone marrow transplants and a series of transfusions to replenish her blood supply as chemotherapy shrinks the tumour to nothing, doctors said.

Toddler Zainab Mughal needs extremely rare blood to beat cancer. Credit:OneBlood

"The results came in and the results were really bad," her father, Raheel Mughal, said in a video. "We were all crying. This was like the worst thing we were expecting."

There was another big complication: Mughal and his wife were tested to see if they were compatible blood donors. They weren't. A parade of family and friends came into the hospital to be pricked by needles. No luck.