Leukemia is a type of blood cancer that is caused by an increase in the number of white blood cells in the body. White blood cells squeeze out the red blood cells and platelets that your body requires to function properly. Cancerous white blood cells don't kill bacteria or virus like normal white blood cells do; instead, they attack the body's own tissue. Leukemia is one of the most common cancers in children and adults. It can be acute or chronic. Acute leukemia means the disease develops quickly and usually does not survive longer than five years. Chronic leukemia is more stable over time. The average life expectancy for people with chronic leukemia is about ten years after diagnosis. People of any age can get leukemia. Children are most commonly affected - about 85% of cases occur before the age of 20. Adults can also get leukemia - around 15% of cases occur after the age of 40. Women are more likely to get leukemia than men - women make up about 9 out of 10 patients diagnosed with the disease. The main risk factors for developing leukemia include having a family member who has the disease, being exposed to radiation, chemicals, or drugs that can cause cancer, and having genetic mutations that lead to cancer development. Genetic mutations can be found in some people who have no known cause for their leukemia.