AML is a rare blood cancer that develops rapidly in the bone marrow. Approximately 3,100 people are diagnosed with AML every year in the UK, and it is more commonly found in people over the age of 60. In AML, the myeloid stem cells do not make normal, healthy blood cells. Instead, it causes abnormal blood cells (in particular two forms of WBCs called granulocytes and monocytes) to grow and divide rapidly, and build up in the blood and bone marrow.

CML is a rare type of cancer where the body makes too many granulocytes (a type of white blood cell). Similar to AML, CML produces abnormal granulocytes that build up in the blood and bone marrow, reducing the production of healthy cells in our blood. Every year, approximately 760 people are diagnosed with CML in the UK. CML develops very slowly, and many people can go months or years without symptoms.

In ALL, either the T- or B-lymphocytes can be affected. ALL is more commonly diagnosed in children and adults over 75, affecting around 800 people in the UK every year. Lymphocytes are white blood cells that are important in fighting and protecting against infections, and in ALL, lymphocytes do not fully develop. Therefore, these abnormal lymphocytes cannot fight against infections.

In the UK, there are approximately 3,700 people diagnosed with CLL every year. A diagnosis of CLL is much more common in older people. B-lymphocytes are the cancerous white blood cells in CLL, where these immature, abnormal lymphocytes build up in the bone marrow, reducing the body's ability to fight infections.