Leukemias are malignant progressive disease in which the bone marrow and other blood-forming organs produce increased numbers of immature or abnormal leucocytes. This is thought to occur after somatically acquired genetic mutations lead to dysregulation and clonal expansion of progenitor cells. Whilst most leukemias involve white blood cells, occasionally other cells are the primary leukemia cells such as red blood cells or platelets.

As disease progression occurs, suppression of normal blood cell production leads to anemia and cytopenia with a host of attendant symptoms and clinical consequences.