A low WBC, or white blood count, is called leukopenia. There are several types of white blood cells, including neutrophils and lymphocytes. White blood cells are the body's main defense against infection, and the function of the immune system can be seriously compromised when the WBC is low, according to the Merck Manuals Online Medical Library. Causes of a low WBC are many, and include disorders and medical treatments that cause defects in the cells.
Aplastic Anemia
Aplastic anemia is a disease of the blood that diminishes the bone marrow's ability to make stem cells that become white cells, red cells and platelets. Many disorders can result when the bone marrow can not make enough new blood cells, explains the National Heart Lung and Blood Institute. Abnormal heart rhythm, enlargement of the heart, bleeding, heart failure and infections can occur. Aplastic anemia can cause death if it is severe. The cause of aplastic anemia is unknown in half of all cases. Known causes include toxins such as arsenic and pesticides, radiation, HIV, chemotherapy, hepatitis and some types of cancer. Blood transfusions, bone marrow transplants and medications treat aplastic anemia.
Systemic Lupus Erythematosus
Systemic lupus erythematosus, or SLE, is a complex autoimmune disorder that affects many body systems. It has a wide range of symptoms, according to the National Institute of Arthritis Musculoskeletal and Skin Diseases. SLE is a chronic inflammatory disease that occurs when the immune system attacks the body's tissues and organs, including WBC production. Many different body systems can be affected, including the skin, joints, blood cells and lungs. Symptoms include low WBC, anemia, arthritis, a red facial rash, seizures, mouth ulcers and abnormal kidney function. The cause is unknown. Treatment focuses on symptom management, such as treatment of infections and medications to reduce inflammation and control immune function.
Cancer Treatment
A low WBC commonly results from cancer treatments such as chemotherapy, radiation treatments, bone marrow transplants and corticosteroid medications, the American Cancer Society explains. Neutrophils are most often affected, and the ability to fight infection is significantly reduced. This is referred to as neutropenia. The usual signs of infection--such as swelling, pain, redness and pus-- are normally caused by the response of white blood cells, and may be absent. Fever may be the only sign of infection, which must be treated promptly.
