What are the common conditions and disorders that affect white blood cells?

There are several conditions and disorders that affect white blood cells. These are some of the more common: 

1. An infection: An infection can result in higher than normal levels of white blood cells. This is because, when you have an infection, white blood cells multiply rapidly in an attempt to destroy the harmful pathogen. 
2. A compromised immune system: Some illnesses such as HIV/AIDS can destroy white blood cells. Too few white blood cells weaken the immune system and increase the risk of infections. Some cancer treatments such as chemotherapy and radiation therapy can also destroy white blood cells and weaken the immune system. 
3. Cancer of the blood: Some types of cancers, such as lymphoma and leukemia, trigger the uncontrolled growth of an atypical type of blood cell in the bone marrow. This profusion of abnormal blood cells in the body greatly increases the risk for various complications, particularly serious bleeding and infections. 
4. Some medications: Some types of medicines have the side effect of increasing or lowering the white blood cell count in the body. 
5. Myelodysplastic syndrome: This condition is associated with the aberrant production of all types of blood cells in the bone marrow, including white blood cells. 
6. Myeloproliferative disorder: Myeloproliferative disorder encompasses a number of different conditions that stimulate the excessive production of immature blood cells. This can lead to an abnormal balance of the different types of blood cells in the bone marrow. As a result, the number of white blood cells in the blood may be higher or lower than the normal range. 
7. Extreme stress: High white blood cell levels may also be triggered by extreme physical stress caused by an injury or emotional distress. 
8. Smoking or even extreme exercise can affect the white blood cells in the body.