Causes

White blood cells are manufactured in bone marrow — the spongy tissue inside some of your larger bones. A low white blood cell count usually is caused by:

• Viral infections that temporarily disrupt the work of bone marrow
• Certain disorders present at birth (congenital) that involve diminished bone marrow function
• Cancer or other diseases that damage bone marrow
• Autoimmune disorders that destroy white blood cells or bone marrow cells
• Severe infections that use up white blood cells faster than they can be produced
• Medications, such as antibiotics, that destroy white blood cells
• Sarcoidosis (collections of inflammatory cells in the body)

Specific causes of a low white blood cell count include:

• Aplastic anemia
• Chemotherapy
• HIV/AIDS
• Hypersplenism (an abnormality of the spleen causing blood cell destruction)
• Kostmann's syndrome (a congenital disorder involving low production of neutrophils)
• Leukemia
• Lupus
• Malnutrition and vitamin deficiencies
• Myelodysplastic syndromes
• Myelokathexis (a congenital disorder involving failure of neutrophils to enter the bloodstream)
• Radiation therapy
• Rheumatoid arthritis and other autoimmune disorders
• Tuberculosis (and other infectious diseases)