Leukaemia is a blood cancer. It affects the white blood cells, which are a really important part of our immune system that fights infection. Acute lymphoblastic leukaemia (ALL) is one of four main types of leukaemia.

What is ALL?

Leukaemia is a cancer of the blood. It affects the white blood cells, which are a really important part of our immune system that fights infection.

There are four main types of leukaemia: acute myeloid leukaemia (AML), acute lymphoblastic leukaemia (ALL), chronic myeloid leukaemia (CML) and chronic lymphocytic leukaemia (CLL).

Different leukaemias are diagnosed according to the type of white blood cell affected and the speed with which the cancer progresses.

ALL is an acute leukaemia meaning that it is more aggressive and progresses quickly. It affects a type of white blood cell called lymphoid cells.

Making blood

White blood cells are made in the bone marrow – the soft tissue in the middle of our bones – where all our blood cells are made. Mother cells, called stem cells, reside here and make every type of blood cell that we need.

Stem cells constantly produce new blood cells to replace old and damaged ones. New cells only leave the bone marrow once they have fully matured. This process is well controlled so that we have just the right amount of each blood cell in our body.

Developing leukaemia

When someone has leukaemia, control of blood cell production breaks down. The stem cells make very large numbers of immature blood cells. In the case of ALL these are abnormal, or cancerous, lymphoid cells. They never mature into proper white blood cells, vital to a healthy immune system, and so people with ALL have an increased risk of infection.

The cancer cells cluster in the bone marrow and prevent other important blood cells from being made. Most of the problems of leukaemia are caused by the lack of normal cells in the blood, rather than the leukaemia cells themselves