Mum Anna described Francis as a “joyful” baby who “hardly ever cried”.
The boy, from Walton, Liverpool, had blood tests after unexplained bruise on his arm at six weeks old.
Initial results failed to reveal anything abnormal but he was then given a bone marrow biopsy when he became very ill.
Anna was told he has acute myeloid leukaemia (AML), which causes marrow to make too many abnormal white blood cells and prevents healthy blood ones. Some 3,100 people in the UK are diagnosed a year with the condition.
Francis’s biopsy showed his bone marrow was 80% cancer cells.
Anna said: “This has completely turned our world upside down. You never think something like this will happen to you, you feel so desperate.
“We’re devastated that Francis is having to face something so young.”
Francis has been admitted to Alder Hey Children’s Hospital in Liverpool where he will undergo chemotherapy before being transferred to Manchester Children’s Hospital in November.
He will need a stem cell transplant as his only chance of a cure.
The family urge people to join the Anthony Nolan stem cell register to find a match – with the charity sending out a cheek swab to see if a person, aged 16 to 30 and in good health qualifies.
Henny Braund, chief executive of Anthony Nolan, said: “It would mean everything to Francis’s family to find him a donor before November.”
