In the majority of cases the cause of Leukemia is unknown. Several factors, however, are known to be associated with the development of Leukemia. These are:
1. Ionizing Radiation: There was an undoubted increase in Leukemia incidence following the atomic bombing of the Japanese cities. A striking increase in Leukemia was also observed after the use of X-ray therapy to control an arthritic condition of the spine called ankylosing spondylitis.
2. Cytotoxic Drugs: These, particularly alkylating agents used in the treatment of cancer may induce Leukemia after a latent period of several years.
3. Exposure to Benzene: This is a chemical compound used in industries.
4. Retrovirus: It has been found to be associated with one type of Leukemia.