My 3-year-old daughter had leukaemia, yet doctors told me she was fine 10 times.

Leukaemia is a cancer that starts in blood-forming tissue, usually the bone marrow.

It leads to the over-production of abnormal white blood cells, which fight off infections.

But a higher number of white blood cells means there is ‘less room’ for other cells, including red blood cells – which transport oxygen around the body – and platelets – which cause blood to clot when the skin is cut.

There are many different types of leukaemia, which are defined according to the immune cells they affect and how the disease progresses.

For all types combined, 9,900 people in the UK were diagnosed with leukaemia in 2015, Cancer Research UK statistics reveal.

And in the US, around 60,300 people were told they had the disease last year, according to the National Cancer Institute.

Most cases have no obvious cause, with the cancer not being contagious or inherited.

Leukaemia generally becomes more common with age – the exception being acute lymphoblastic leukemia, which peaks in children.

Other risk factors include being male, exposed to certain chemicals or radiation, and some bone-marrow disorders.

Symptoms are generally vague and get worse over time.

These can include:

• Tiredness
• Frequent infections
• Sweats
• Bruising
• Heavy periods, nose bleeds or bleeding gums
• Palpitations
• Shortness of breath

Acute leukaemia – which progresses rapidly and aggressively – is often curable via chemo, radiotherapy or a stem cell transplant.

Chronic forms of the disease – which typically progress slowly – tend to incurable, however, these patients can often live with the disease.