An urgent appeal has been launched to find a stem cell donor for a London firefighter's four-year-old son.
Tommy Simpson, who was diagnosed with leukaemia last month, has been in hospital since Christmas.
His white British and black Caribbean heritage means a donor match is harder to find, the African Caribbean Leukaemia Trust (ACLT) said.
His parents, London firefighter Nigel and Maxine, are pleading for donors to come forward as no family members have been found to be suitable matches.
London Fire Brigade has backed the appeal, in support of Mr Simpson who works as a firefighter in the capital.
The ACLT is leading the campaign using the hashtag #Match4Tommy.
They said: "We know the window of opportunity for an unrelated match being found is going fast with each day passing, that's why we are appealing for people to join the stem cell register now."
Tommy, who is being treated for Acute Myeloid Leukaemia at Great Ormond Street Hospital in London, is awaiting test results to see if he will need a life-saving bone marrow transplant.
A number of donor registration drives are being held in the hope of finding a match, with the first held in Croydon on Saturday and another due to take place in Leicester Square on March 19.