Leukemia develops when bone marrow produces too many abnormal white blood cells, but the exact trigger varies by type

Leukemia is not a single disease with one cause. It starts when something goes wrong in the cells that make blood, usually in bone marrow. The cells begin dividing uncontrollably and crowding out healthy blood cells. Researchers have identified certain risk factors and conditions that make leukemia more likely, but they cannot yet predict who will develop it or prevent it in most cases. Understanding what is known about causes can help you talk with doctors about your own risk.

Key Takeaways

  • Leukemia occurs when bone marrow cells start dividing abnormally, but no single cause has been found that applies to all types.
  • Radiation exposure, certain chemicals, and some inherited genetic conditions increase the risk of developing leukemia.
  • Most people with leukemia have no known risk factor, meaning the disease can develop in anyone.
  • Viral infections, particularly human T-lymphotropic virus (HTLV-1), are linked to specific types of leukemia in some populations.
  • Age, sex, and family history matter for risk, but having a risk factor does not mean someone will develop leukemia.

Genetic mutations and how cells go wrong

Leukemia always involves genetic mutations—changes in the DNA of blood-forming cells. These mutations tell cells to divide when they should stop, or to ignore signals that would normally cause them to die. The mutations are not inherited from parents in most cases; they happen randomly in a single cell during a person's lifetime. That cell then divides repeatedly, creating millions of copies of itself.

Different types of leukemia involve different mutations. Chronic myeloid leukemia (CML) almost always involves a specific mutation called the Philadelphia chromosome. Acute promyelocytic leukemia (APL) typically has a different mutation. Researchers continue to identify new mutations linked to leukemia, which has led to targeted treatments that work against specific mutations rather than treating all leukemias the same way.

Radiation as a known risk factor

High-dose radiation exposure increases leukemia risk. This was documented in survivors of the atomic bombings in Japan during World War II and in people who received radiation therapy for other cancers. The risk depends on the dose, the person's age at exposure, and how much time has passed since exposure. Children exposed to radiation face higher risk than adults exposed to the same dose.

Medical imaging like X-rays and CT scans uses much lower radiation doses than those linked to leukemia risk. The benefit of diagnosing a medical problem usually outweighs the small risk from the radiation itself. Occupational exposure to radiation (such as in some medical or nuclear work) is monitored and limited to keep doses low.

Chemical exposures and occupational hazards

Certain chemicals increase leukemia risk when exposure is heavy or prolonged. Benzene, used in manufacturing and found in gasoline, is the chemical most clearly linked to leukemia. Workers in oil refining, shoe manufacturing, and chemical plants who were exposed to high benzene levels have shown increased leukemia rates. Current workplace safety standards limit benzene exposure to reduce this risk.

Other chemicals under study include formaldehyde, pesticides, and some solvents, though the evidence is less clear than for benzene. Most people exposed to these chemicals at low levels—such as from consumer products or occasional contact—do not develop leukemia. The dose and duration of exposure matter significantly.

Viral infections linked to specific leukemia types

Human T-lymphotropic virus type 1 (HTLV-1) is associated with adult T-cell leukemia, particularly in people from Japan, the Caribbean, and parts of Africa where the virus is more common. Most people infected with HTLV-1 never develop leukemia, but the virus increases risk substantially. The virus is spread through blood transfusion, sexual contact, and from mother to child during breastfeeding.

Epstein-Barr virus (EBV) is linked to certain types of lymphoma and leukemia, especially in people with weakened immune systems. Human immunodeficiency virus (HIV) increases the risk of certain blood cancers, though modern HIV treatment has reduced this risk significantly. These viral connections have led researchers to study whether preventing or treating the virus might prevent the cancer.

Inherited genetic conditions that raise risk

Some people inherit genetic conditions that make leukemia more likely. Down syndrome (trisomy 21) carries a higher leukemia risk, particularly acute myeloid leukemia (AML) in children. Fanconi anemia, a rare inherited disorder affecting DNA repair, significantly increases leukemia risk. Neurofibromatosis type 1 and Li-Fraumeni syndrome (a mutation in the TP53 gene) also raise risk.

These inherited conditions are rare, and most people with them do not develop leukemia. However, people with these diagnoses are often monitored more closely and may have screening tests to catch blood problems early. If you have a family history of leukemia or a known inherited condition, discussing screening options with your doctor is worthwhile.

Age and sex patterns in leukemia development

Leukemia can develop at any age, but patterns differ by type. Acute lymphoblastic leukemia (ALL) is most common in children under age 5, with a second peak in older adults. Acute myeloid leukemia (AML) becomes more common with age, with most cases occurring in people over 65. Chronic leukemias typically appear in middle-aged and older adults.

Men develop leukemia more often than women, though the reason is not fully understood. This difference appears across most types of leukemia. Age-related changes in bone marrow and the immune system likely contribute to higher rates in older people, but this does not mean aging itself causes leukemia—most older people never develop it.

Why most people with leukemia have no clear cause

The majority of people diagnosed with leukemia have no known risk factor. They were not exposed to high radiation, did not work with benzene, do not have an inherited condition, and have no family history of leukemia. This does not mean the cause is unknown in a scientific sense—mutations still occurred in their bone marrow cells—but it means doctors cannot point to a specific exposure or condition that led to those mutations.

This reality is important because it means leukemia is not something a person caused through their choices or lifestyle. It also means that identifying risk factors in research does not translate to prevention strategies for most people. Current research focuses on understanding the mutations themselves and developing treatments that target them, rather than preventing the disease before it starts.

Frequently Asked Questions

Can leukemia run in families?

Most leukemia is not inherited. However, some inherited genetic conditions like Fanconi anemia or Li-Fraumeni syndrome increase leukemia risk. If multiple family members have had leukemia, genetic counseling can help determine whether an inherited condition might be involved. Most families with one leukemia case do not have an inherited pattern.

Does stress or lifestyle cause leukemia?

There is no scientific evidence that stress, diet, exercise, or lifestyle choices cause leukemia. These factors matter for overall health, but they are not linked to leukemia development. Leukemia results from mutations in bone marrow cells, not from behaviors or emotional factors.

If my parent had leukemia, will I get it?

Not necessarily. Most leukemia is not inherited. Your risk may be slightly higher than the general population, but most children of leukemia patients never develop the disease. If your parent's leukemia was linked to an inherited genetic condition, genetic testing can clarify your own risk.

Can leukemia be prevented if I know my risk factors?

If you have a known risk factor like occupational benzene exposure, reducing that exposure can lower your risk. For most other risk factors, there is no proven prevention strategy. People with inherited conditions or strong family histories may benefit from monitoring, but prevention is not yet possible for most types of leukemia.

Does living near power lines or using cell phones cause leukemia?

Extensive research has not found a link between leukemia and power lines, cell phones, or other sources of non-ionizing radiation. The radiation from these sources is different from the high-energy radiation (like X-rays) that has been linked to leukemia risk. This remains an area of ongoing study, but current evidence does not support a connection.