Myeloid leukemia (usually meaning acute myeloid leukemia, AML) is caused by genetic damage in bone marrow stem cells that makes immature myeloid cells grow out of control instead of maturing into healthy blood cells. In most people, there is no single clear trigger, but several known risk factors can increase the chances that these mutations develop over time.

What actually happens in the body

  • AML starts when DNA changes (mutations) occur in early myeloid stem cells in the bone marrow, leading them to multiply rapidly and fail to mature.
  • These abnormal cells crowd out normal red cells, white cells, and platelets, which causes symptoms like infections, fatigue, and bleeding.

Main known risk factors

  • Age and sex : AML is more common in older adults and slightly more common in men.
  • Previous blood disorders : Conditions such as myelodysplastic syndromes, myelofibrosis, polycythaemia vera, or essential thrombocythaemia can evolve into AML.
  • Inherited genetic syndromes : Down syndrome, Fanconi anemia, Li–Fraumeni syndrome and a few others raise lifetime AML risk, though AML is still rare overall.

Environmental and lifestyle causes

  • Benzene exposure : Long-term exposure to benzene (in some industrial solvents, petrol, and certain workplaces) is a well‑established AML risk factor.
  • Radiation : High‑dose radiation (atomic incidents or some older forms of radiotherapy) increases risk.
  • Smoking : Cigarette smoke contains benzene and other carcinogens that damage bone marrow DNA and are linked to higher AML risk.

Medical treatment–related causes

  • Previous chemotherapy and radiotherapy : Some people develop “treatment‑related AML” years after receiving certain chemotherapy drugs (like alkylating agents or topoisomerase II inhibitors) and/or radiotherapy for another cancer.
  • This happens because these treatments, while killing cancer cells, can also injure the DNA of healthy bone marrow stem cells in a small minority of patients.

When there is no obvious cause

  • For many people with AML, no identifiable risk factor is ever found, even after detailed evaluation.
  • Most people who have one or more risk factors (for example, smokers or people with past chemotherapy) never develop AML, which shows that risk factors increase probability but do not guarantee the disease.

If you or someone close has myeloid leukemia, the exact cause in that individual is often impossible to pinpoint; doctors usually talk about “risk factors” and “mutations” rather than a single cause.

TL;DR: Myeloid leukemia is driven by DNA mutations in bone marrow myeloid stem cells, influenced by age, certain inherited conditions, prior blood diseases, some chemicals (benzene), smoking, radiation, and some past cancer treatments—yet in many cases, the precise cause remains unknown.

Information gathered from public forums or data available on the internet and portrayed here.