White blood cells play many vital roles, primarily within the immune system. Also called leukocytes, white blood cells are sent through the bloodstream when the immune system detects foreign invaders such as viral or bacterial infections and then lead the fight against the illness- or disease-causing cells. In healthy individuals, the body constantly produces new white blood cells, but many factors can lead to lower-than-normal counts and wide-ranging adverse effects.

Problems with Bone Marrow

Bone marrow, the innermost layer of bones, is a spongy substance responsible for producing blood cells. Often, low white blood cell counts are a result of problems with this tissue. Cancer and infections can disrupt the bone marrow processes, as can treatments such as radiation.

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Viral Infections

Viral infections such as HIV can have an impact on white blood cell production, disrupting production and, thus, making it more difficult for the immune system to do its job. Opportunistic infections are those normally easily prevented but can cause illness in people with compromised immune systems, such as those with HIV and AIDS. Occasionally, even relatively common and minor respiratory viruses can make their way to the bone marrow, lowering the white blood cell count and making it harder for the body to defend itself.

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Congenital Disorders

Congenital disorders are disorders present when a child is born; they are often life-long conditions. Kostmann syndrome or congenital neutropenia is one such condition. It causes reduced neutrophils, a type of white blood cell. Myelokathexis causes neutrophilia as well as leukopenia or reduced circulation of white blood cells. Often, if a person with one of these conditions is diagnosed with a low white blood cell count later in life, they already are aware of the cause.

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Leukemia is a type of cancer that takes many forms and most commonly affects children. It attacks the tissues that form blood and produce blood cells. For this reason, the bone marrow and lymphatic system are impacted most significantly. Leukemia causes the bone marrow to produce irregular white blood cells that do not function correctly, leaving the body open to infection.

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Radiation Therapy

Cancer itself can be a cause of a low white blood cell count, but so can the radiation therapy used to combat it. Radiation therapy uses beams of energy (usually X-rays or protons) to destroy cancer cells. This same energy can also destroy healthy cells, which can lead to a lower white blood cell count. Factors like the region being treated, the dose of radiation, and the frequency of treatment can influence the effects on the immune system. Normal cells can usually repair the damage caused by radiation therapy, but some patients require additional treatments to help increase the white blood cell count.

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Chemotherapy is another cancer treatment that can decrease white blood cell count. This treatment method eliminates fast-growing cells, such as cancer cells, in the body and is considered an extremely effective method of combating the disease. However, like radiation, it can also cause a lot of collateral damage. It makes the body weaker and often takes a toll on some noncancerous cells.

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Lupus is an autoimmune disease, which means it makes the immune system misidentify and attack its own organs and tissues. The chronic condition causes inflammation and can affect many parts of the body, both inside and out. Skin, joints, kidneys, the brain, the heart, and the lungs can all be affected by lupus, as can blood cells. Lupus is difficult to diagnose, as it presents with the same symptoms as several other disorders. There is currently no cure for the disease, and no two cases are alike.

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Malnutrition and vitamin deficiency can cause a wide range of health problems, including a low white blood cell count. If the body does not have the vitamins and nutrients it needs, it cannot carry out vital processes such as the production of red or white blood cells. Causes of malnutrition include eating disorders such as anorexia or binge eating, but even people who eat enough calories can develop deficiencies due to the types of foods they are consuming. Vitamins B6, B12, C, D, and iron top the list of the most common deficiencies in the US.

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Rheumatoid Arthritis

Rheumatoid arthritis is a chronic inflammatory disorder. Like other types of arthritis, it affects the joints, but it can also damage the eyes, skin, lungs, heart, and blood vessels. The autoimmune disorder can lead to painful swelling when the body begins to attack its own, otherwise healthy tissues. As with lupus, this can lead to a low white blood cell count. Additionally, disease-modifying antirheumatic drugs (DMARDs) can leave patients vulnerable to infection.

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Infections and diseases can cause a low white blood cell count, but like chemotherapy, sometimes treatments are to blame. Antibiotics can lead to reduced numbers of white blood cells for a similar reason as cancer treatments: they inadvertently destroy healthy cells while fending off foreign bodies. Luckily, in most cases where medication is the cause of low white blood cell count, levels return to normal once the person has completed their course.

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