Acute lymphoblastic leukaemia (ALL) is rare, but anyone can get it.
It's not always clear what causes it.
You might be more likely to get it if:
- you're a child or young adult – it's most common in children aged 4 and under
- you have a genetic condition such as Down's syndrome
- you've had certain types of chemotherapy treatment in the past
- you were exposed to a lot of radiation or had radiotherapy treatment in the past, especially when you were a child
- you are exposed to high levels of a chemical called benzene
- you have a weakened immune system, for example you have HIV
It's important to get any symptoms of acute lymphoblastic leukaemia checked by a GP.
