The operation - the first of its kind in the UK - took place at Glasgow's Royal Hospital for Sick Children on 4 April and yesterday the Asian boy, named only as Bilal, was allowed home.
Another operation has also taken place at Great Ormond Street Hospital, London on 23 April, on seven-year-old Vijay Negi, from North London, who suffers a rare form of anaemia.
Bilal has suffered from leukaemia since birth and efforts to find a matching bone marrow donor from either the British Bone Marrow or the Anthony Nolan panels failed.
When his brother, Aadil, was born in January, stem blood cells were taken from the umbilical cord and frozen. When they were found to be a perfect match - and after Bilal had chemotherapy to clear his bone marrow - 100 millilitres of blood was transfused into him by the consultant haematologist, Dr Brenda Gibson. Yesterday he was pronounced well enough to leave hospital.
"I think if he stays in remission for a year, we would feel reasonably confident that [the leukaemia] is not going to return", said Dr Gibson.
Vijay Negi - who suffers from the "extremely rare" Fanconi Anaemia - had the transfusion after cord blood cells were collected by the National Blood Transfusion Service following the birth of his sister. He was yesterday said to be making a "very good recovery" at Great Ormond Street.
Stem cells are "all-purpose" blood cells found in the bone marrow and other blood-forming tissues which can develop into the various types of white blood cell found in the immune system. Recently it was discovered that a transplant of stem cells from the umbilical cord may provide a better weapon than bone marrow against leukaemia.Reuse content