What is Acute Leukaemia?

Acute leukaemia is a type of cancer that begins in the bone marrow, the soft, spongy tissue inside your bones where your body produces blood cells. The word “acute” refers to how quickly the disease progresses, creating immature blood cells rather than mature, functioning ones. Unlike chronic forms that develop slowly over years, acute leukaemia advances rapidly and requires immediate treatment.^[1]

In healthy bone marrow, blood cells develop through multiple stages before reaching their mature forms. These include red blood cells that carry oxygen, white blood cells that fight infections, and platelets that help blood clot. In acute leukaemia, however, the bone marrow produces abnormal cells called blasts or immature cells. These abnormal cells multiply rapidly and take over the space in your bone marrow, crowding out the normal, healthy cells.^[2]

There are two main types of acute leukaemia, classified based on which type of white blood cell is affected. Acute lymphoblastic leukaemia (ALL) affects lymphocytes, which are white blood cells that help fight infections. Acute myeloid leukaemia (AML) affects myeloid cells, which normally develop into red blood cells, platelets, and certain types of white blood cells. Each type behaves differently and requires specific treatment approaches.^[3]

How Common is Acute Leukaemia?

Acute leukaemia is considered a rare type of cancer, but it remains the most common form of acute leukaemia in adults. Around 3,100 people are diagnosed with acute myeloid leukaemia each year in the United Kingdom. In the United States, acute lymphoblastic leukaemia is the most common type of cancer in children, though it can also occur in adults.^[1][3]

The risk of developing acute leukaemia varies by age. Acute myeloid leukaemia most commonly affects people over 75 years old, though it can occur at any age. Acute lymphoblastic leukaemia, while being the most common childhood cancer, also affects adults, though the chance of cure is greatly reduced in older patients. Each year, approximately 1,160 children receive an AML diagnosis in the United States.^[3][12]

The disease affects slightly more males than females in some types, and there can be variations in incidence rates across different populations. Understanding these patterns helps healthcare providers identify those who might be at higher risk and need closer monitoring or earlier intervention.^[2]

What Causes Acute Leukaemia?

Acute leukaemia occurs when changes, called mutations, happen in the genetic material or DNA of bone marrow cells. A cell’s DNA contains instructions that tell the cell what to do and how to function. When these instructions become damaged or altered, cells can begin to grow and divide out of control, creating the abnormal blast cells that characterize leukaemia.^[1]

Experts are not entirely sure what triggers these genetic changes in most cases. The mutations may happen during a person’s lifetime when something alters their DNA, or they may occur if someone inherited a genetic disorder that increases their risk. In rare cases, changes in certain genes in biological parents’ sperm or egg cells can be passed down to children.^[12]

These genetic changes disrupt the normal production line of your bone marrow. Instead of creating the exact number of healthy blood cells your body needs, the bone marrow starts producing abnormal myeloid or lymphoid blasts. These immature cells don’t function like normal blood cells. They cannot carry oxygen, fight infections properly, or help your blood clot when needed. As they multiply rapidly, they fill up the bone marrow, leaving little room for healthy cells to develop.^[2]

Risk Factors for Acute Leukaemia

While most cases of acute leukaemia have no identifiable cause, certain factors can increase a person’s risk of developing the disease. These risk factors don’t directly cause cancer but may increase the chance of DNA damage in cells that could lead to leukaemia.^[7]

Previous cancer treatment is one significant risk factor. People who have undergone chemotherapy or radiotherapy for another type of cancer have an increased risk of developing acute leukaemia later in life. This is because these treatments, while effective at killing cancer cells, can sometimes damage the DNA of healthy bone marrow cells as well.^[3][7]

Exposure to very high levels of radiation, including previous radiotherapy treatment, increases risk. This includes exposure from nuclear accidents or nuclear weapons, though such exposure is extremely rare. Smoking and other exposure to benzene, a chemical used in manufacturing and found in cigarette smoke, also raises the likelihood of developing acute leukaemia.^[3]

Certain blood disorders and genetic conditions can predispose individuals to acute leukaemia. People with Down’s syndrome or other chromosomal abnormalities have a higher risk. Additionally, having a pre-existing blood disorder, such as myelodysplastic syndrome, increases the chance of developing acute leukaemia over time.^[3]

Symptoms of Acute Leukaemia

The symptoms of acute leukaemia usually develop over a few weeks and become progressively worse over time. Many early symptoms can feel similar to having a cold or flu, which is why people sometimes delay seeking medical attention. However, unlike flu symptoms that eventually improve, symptoms of acute leukaemia persist and worsen.^[3]

One of the most common symptoms is extreme tiredness and weakness. This happens because there are not enough healthy red blood cells to carry oxygen throughout the body, a condition called anaemia. People often describe feeling exhausted even after rest, or finding that everyday activities that were once easy now leave them breathless and fatigued.^[3]

Easy bruising or bleeding is another key warning sign. Because acute leukaemia affects platelet production, the blood cannot clot properly. People may notice frequent nosebleeds, bleeding gums when brushing teeth, or bruises appearing without any remembered injury. Small red or purple spots called petechiae may appear on the skin. Women might experience unusually heavy menstrual periods.^[1][12]

Frequent or severe infections occur because there are not enough healthy white blood cells to fight off bacteria, viruses, and other germs. People with acute leukaemia may develop infections that don’t go away or keep coming back despite treatment. Fever without an obvious cause is common, as is feeling generally unwell.^[3]

Other symptoms can include bone or joint pain, particularly in the long bones of the arms and legs. Swollen lymph nodes may appear in the neck, armpits, abdomen, or groin. Some people experience unexplained weight loss and loss of appetite. Paleness of the skin, night sweats, headaches, dizziness, and shortness of breath are also frequently reported.^[1][12]

Because acute leukaemia progresses rapidly, symptoms can appear suddenly and become severe quickly. If you or your child experiences persistent symptoms that concern you, particularly if they seem to be getting worse rather than better, it is important to see a doctor promptly. Early diagnosis and treatment can make a significant difference in outcomes.^[1]

Preventing Acute Leukaemia

Unlike some other cancers, there are no proven ways to prevent most cases of acute leukaemia because the exact cause remains unknown in the majority of cases. Since many cases occur without any identifiable risk factors, and the genetic changes that trigger the disease happen spontaneously, prevention strategies are limited.^[3]

However, reducing exposure to known risk factors where possible may help lower your risk. Not smoking or quitting smoking is one of the most important steps, as smoking exposes you to benzene and other harmful chemicals that can damage bone marrow cells. Avoiding occupational exposure to benzene and other toxic chemicals, through proper workplace safety measures and protective equipment, may also reduce risk.^[3]

For people who require cancer treatment with chemotherapy or radiotherapy, the benefits of treating their current cancer far outweigh the small risk of developing acute leukaemia years later. Doctors carefully consider the type and dose of treatment to maximize effectiveness while minimizing long-term risks. Following your treatment plan as prescribed and attending follow-up appointments allows your medical team to monitor your health over time.^[7]

If you have a blood disorder or genetic condition that increases your risk of acute leukaemia, regular monitoring by your healthcare team is essential. They may recommend periodic blood tests to watch for early signs of changes that could indicate leukaemia development. Early detection allows for prompt intervention when treatment is most likely to be effective.^[3]

How Acute Leukaemia Affects the Body

To understand how acute leukaemia affects the body, it helps to know what happens in healthy bone marrow. Normally, bone marrow acts like an efficient production line, making blood stem cells that mature into red blood cells, white blood cells, and platelets in precisely controlled numbers. This process, called haematopoiesis, ensures your body always has enough of each type of blood cell to function properly.^[2]

In acute leukaemia, genetic mutations cause blood stem cells to develop abnormally. Instead of maturing properly, they become stuck in an immature state as blast cells. These blast cells multiply rapidly and uncontrollably, flooding the bone marrow. Because they take up so much space, there is little room left for normal blood stem cells to mature into functional blood cells.^[4]

The consequences of this disrupted blood cell production affect multiple body systems. With fewer red blood cells, tissues and organs don’t receive enough oxygen, leading to fatigue, weakness, and shortness of breath. The reduced number of healthy white blood cells means the immune system cannot fight infections effectively, making people vulnerable to bacteria, viruses, and fungi that a healthy immune system would normally control. The shortage of platelets impairs blood clotting, resulting in easy bruising, bleeding, and potentially dangerous haemorrhages.^[2]

The leukaemia cells themselves serve no useful purpose. They cannot carry oxygen like red blood cells, fight infections like white blood cells, or help blood clot like platelets. They are essentially defective cells that crowd out the cells your body needs to function. As they accumulate, they can spill out of the bone marrow into the bloodstream and may spread to other organs such as the lymph nodes, spleen, liver, brain, and spinal cord.^[2]

This expansion of leukaemia cells explains why acute leukaemia is considered a medical emergency. The disease progresses quickly, and without treatment, the accumulation of blast cells and loss of normal blood cells can lead to life-threatening complications such as severe infections, uncontrolled bleeding, or organ failure. This is why treatment typically begins within days of diagnosis.^[3][10]