The mother of a three-year-old girl has issued an urgent appeal for people to tested for stem cell donation to see if they can save her daughter's life.
Ava Stark, who has a rare blood disorder, was just 24 hours from going to hospital to prepare for a transplant when her family was told the donor had to pull out for medical reasons.
It was the second time she had lost out on a potentially life-saving transplant in four months.
Like Ava, there are many people in the same situation who are relying on a donor match being found through a register.
Why are bone marrow/stem cell donors needed?
Bone marrow is a soft tissue found in the middle of certain bones. It contains stem cells, which are the "building blocks" for other normal blood cells (like red cells, which carry oxygen, and white cells, which fight infection).
Some diseases, such as leukaemia, prevent people's bone marrow from working properly. And for certain patients, the only cure is to have a stem cell transplant from a healthy donor.
What does donation involve?
The majority of people donate their stem cells in a painless process similar to giving blood, called peripheral blood stem cell collection.
One in 10 donors will have their stem cells collected via the bone marrow itself, under general anaesthetic.
To be added to the register, you need to be prepared to donate your stem cells via either method.
Who can join the register?
Healthy adults aged between 16 and 30 can sign up for a simple, pain-free test through the Anthony Nolan Trust.
People joining the charity's register must:
weigh over 7st 12lbs (50kg)
have a body mass index (BMI) lower than 40
Not have certain conditions such as heart disease, epilepsy, or autoimmune conditions (click here for a full list)
Potential donors will first be sent a kit in the post so they can provide a saliva sample to be tested
Potential can also register with DKMS. DKMS s the world's largest donor centre, with more than six million registered donors worldwide.
Shortage of young men and ethnic minorities donors
Young men are particularly urged sign up. They produce more stem cells than women and are six times more likely to donate, but make up just 15% of the Anthony Nolan register.
There are also particular shortages of people from black and minority ethnic backgrounds.
South Asian (Indian, Pakistani, Sri Lankan and Bangladeshi origin)
Jewish people of European descent
Southern European (such as people of Greek, Italian and Spanish origin)
What about older donors?
And if you are 17 to 40 (registered before your 41st birthday) and a blood donor, you can join the British Bone Marrow Registry.
Males, females, Black, Asian, minority and mixed ethnicity backgrounds are particularly sought due to shortages of suitable donors on the registry.
The charity Delete Blood Cancer UK, also accept takes people aged 17-55.