Acute myeloid leukaemia (AML) is a form of cancer which affects a type of blood cell called myeloid cells. Myeloid cells include red blood cells, platelets and certain types of white blood cells. As blood cells are made in the bone marrow, the cancer will be present in your bone marrow and in your blood.
In this section you can find out more about how your body works and how AML develops.
What is acute myeloid leukaemia (AML)?
Acute myeloid leukaemia (AML) is a type of blood cancer. In AML, the cells in the bone marrow that produce myeloid cells become cancerous.
AML is a form of cancer which affects a type of blood cell called myeloid cells, which include red blood cells, platelets and certain types of white blood cells. When you have AML, it stops you making enough of these blood cells, which makes you unwell. The symptoms you get will depend on the type of blood cell your body isn’t making enough of.
As blood cells are made in the bone marrow, the cancer will be present in the bone marrow and in the blood.
How AML develops
All leukaemias start in stem cells or progenitor cells. This happens when the cells don’t mature properly and remain immature. These cells have a distinctive appearance when a specialist looks at your bone marrow cells under a microscope.
Every day we make around 10 billion new blood cells, and the information which controls how these blood cells grow up is held within our DNA. Every time a cell divides, the entire DNA code has to be copied exactly, and mistakes are made by chance.
AML develops when there are errors in the information that controls how blood cells grow up. It usually takes mistakes in several key genes that control blood production to cause AML.
Types of AML
AML is one of several different types of acute leukaemia. Acute promyelocytic leukaemia (APL, also known as APML) is a type of AML. About 15% of all cases of AML are part of this specific type.
Watch Professor Paresh Vyas, Consultant Haematologist at John Radcliffe Hospital, Oxford, talk about how AML develops.
What causes AML?
When you’re diagnosed with any cancer, one of the first things you might think is: ‘why me?’ In many cases, we still don’t know what causes AML. We know that some things that we can’t change have an impact on AML, like age and gender. We also know that there are some rare external factors which can have an impact, like exposure to radiation or chemicals. Sometimes, you can also be at an increased risk of getting AML if you’ve got a related blood condition, or if you’ve been treated for a different cancer in the past.
We’re now beginning to understand why age is important. As you get older, you have more time to acquire the errors in your DNA which can cause AML. People of all ages can develop AML, but you’re more likely to get AML above the age of 60. Around a quarter of people who are diagnosed are under 65.
In some very rare cases, children can develop AML – this is called childhood AML.
Slightly more men than women develop AML. We don’t know why.
In most cases, AML doesn’t run in families. However, rarely, in some families there are more cases of AML than we’d expect to occur by chance.
If you’re concerned about this, do discuss it with your doctor.
Radiation and chemical exposure
Exposure to very high radiation levels increases the risk of developing AML. Hardly anyone is exposed to these levels of radiation in normal everyday life.
Exposure to certain other chemicals could also increase the risk of getting AML. One of these chemicals is called benzene, which is found in cigarette smoke and exhaust fumes. Whilst smoking cigarettes has been reported to increase the risk of getting AML, exhaust fumes don’t have enough benzene to pose a risk.
If you have another condition which affects the production of myeloid cells, you can be at higher risk of getting AML. In these cases, the cancer is called secondary AML. This is especially true if you’re over the age of 60. Between 25–40% of AML cases in over 60s can be linked to a previous condition. These conditions are called antecedent haematological disorders.
Some patients can develop AML after being treated for another illness with either chemotherapy and/or radiotherapy.
This type of AML is called treatment-related AML (tAML). Certain types of chemotherapy and radiotherapy are more likely to cause this than others.
Your chance of developing tAML is based on the type of treatment you originally had for the other illness or cancer. The risk of getting tAML is highest between five and eight years after receiving treatment for the other cancer, but some patients can develop it earlier.
Watch Professor Paresh Vyas, Consultant Haematologist at John Radcliffe Hospital, Oxford, talk about who gets AML and what causes it.
Blood and bone marrow
Blood is composed of two parts: a part called plasma, and your blood cells, which are made in the bone marrow. You could think of your bone marrow as being like a factory. This factory needs to make fresh blood cells every day so you can survive, because some blood cells only live for a day or two.
The blood has four important functions:
Red blood cells (erythrocytes) transport oxygen around the body. Inside these red cells is a pigment called haemoglobin that carries the oxygen.
Blood transports other things in plasma, such as food, water and proteins to different parts of your body. Blood also carries waste chemicals to the kidneys and lungs so they can get rid of them.
Defence is a very important function of blood. The defence system is controlled by the white cells, called leukocytes, which are also made in the bone marrow (the soft spongy material inside your bones). The white cells are a part of your immune system and fight infections. There are different types of white cells; the important white cells that you need on a daily basis are called neutrophils, which fight bacteria and fungi.
If you don’t have enough white blood cells in your body, or if they don’t work correctly, as happens with many types of blood cancer including AML, this can mean your defence system doesn’t work as well as it should and you may be more likely to pick up infections.
Whenever you damage or break one of your blood vessels, there are ways your body will stop you from bruising and bleeding. The initial protection against bruising and bleeding is managed by blood cells called platelets, made by your bone marrow. These live for one or two days, and proteins known as clotting factors help support platelets in stopping bruising and bleeding.
Organs in the body release hormones into the blood which send messages to other organs. This isn’t affected by AML.
Bone marrow and how blood cells are made
All blood cells are made in the soft material inside your bones (called the bone marrow). All blood cells are made from a group of parent cells called blood stem cells.
All of us have around 10,000 stem cells. Most of the time these stem cells are asleep. Stem cells live with you for your whole life and are unique because they can make all blood cells. Occasionally they will divide and make cells that are called progenitor cells.
The progenitor cells don’t live as long, but they grow a lot and make sure you can make enough blood cells for everyday life.
There are two types of progenitor cells: myeloid and lymphoid. They give rise to immature cells called blasts. These blast cells steadily grow up into mature cells: red cells, platelets and white blood cells, which are then released by your bone marrow into your blood.
We group together some of these blood cells into what are called myeloid cells. Myeloid cells are red blood cells, platelets and all white blood cells, except one type of white blood cell called lymphocytes. It’s these myeloid cells that are affected in AML.