Conditions such as aplastic anemia, leukemia, lupus, HIV and malnutrition can result in a low white blood cell count, according to Mayo Clinic. If a patient has a viral infection that impairs the normal function of the bone marrow, an autoimmune disorder that damages white blood cells, takes medication that damages the bone marrow, or has a strong infection that destroys white blood cells quicker than they can be produced, his white blood cell count is also greatly affected.
Leukopenia is a medical term for having a decreased amount of leukocytes or white blood cells, reports Healthgrades. Some patients have a lower white blood cell count than the average person, and the usual range of white blood cell count also varies by gender and age. The importance of having a low white blood cell count depends on a patient's overall nutrition, medical history and the underlying condition he has. Many prescription drugs, including those used in chemotherapy, can disrupt the normal production of white blood cells.
Neutropenia, or having a decreased amount of neutrophils, is another medical term for having a low white blood cell count, according to MedlinePlus. Exposure to radiation and disorders such as rheumatoid arthritis, Crohn's disease and tuberculosis can also destroy white blood cells.