Print OverviewYour body produces white blood cells (leukocytes), which help fight bacterial infections, viruses and fungi. If your child has too few or too many white blood cells, in general, here's what it means: Low white blood cell count (leukopenia) means having too few leukocytes circulating in the blood. A long-term low white blood cell count increases the risk of infections and may be caused by a number of different diseases and conditions. High white blood cell count (leukocytosis) means having too many leukocytes circulating in the blood, usually from having an infection. A number of different diseases and conditions may cause a long-term high white blood cell count. There are several types of white blood cells, each with a different disease-fighting activity. The main types are: Neutrophils Lymphocytes Monocytes Eosinophils Basophils White blood cell disorders involving a specific type of white blood cell include: Neutropenia. Neutropenia (noo-troe-PEE-nee-uh) is a low number of neutrophils, a type of white blood cell that fights infections of fungi and bacteria. Neutropenia can be caused by cancer or by diseases, disorders or infections that damage bone marrow. In addition, certain medications and other diseases or conditions can cause neutropenia. Lymphocytopenia. Lymphocytopenia (lim-foe-sie-toe-PEE-nee-uh) is a decrease in lymphocytes, the type of white blood cell that, among other tasks, protects your body from viral infections. Lymphocytopenia can result from an inherited syndrome, be associated with certain diseases, or be a side effect from medications or other treatments. Monocyte disorders. Monocytes help get rid of dead or damaged tissue and regulate your body's immune response. Infections, cancer, autoimmune diseases and other conditions can cause an increased number of monocytes. A decreased number can be the result of toxins, chemotherapy and other causes. Eosinophilia. Eosinophilia (e-o-sin-o-FIL-e-uh) is a higher than normal number of eosinophil cells, a type of disease-fighting white blood cell. Eosinophilia can be caused by a variety of conditions and disorders, most commonly by an allergic reaction or a parasitic infection. Basophilic disorders. Basophils account for only a small number of white blood cells, but they have a role in wound healing, infection and allergic reactions. A decreased number of basophils can result from allergic reactions or infections. An increased number can be caused by certain types of blood cancer or other disorders. Products & ServicesA Book: Mayo Clinic Family Health BookNewsletter: Mayo Clinic Health Letter — Digital EditionShow more products from Mayo Clinic By Mayo Clinic Staff Pediatric white blood cell disorders care at Mayo Clinic Request an appointment Doctors & departments April 19, 2022 Print Living with pediatric white blood cell disorders? Connect with others like you for support and answers to your questions in the Blood Cancers & Disorders support group on Mayo Clinic Connect, a patient community. Blood Cancers & Disorders Discussions Anybody else have Factor V Leiden? 44 Replies Mon, Dec 02, 2024 chevron-right Hodgkin Lymphoma was stable, now new activity 25 Replies Mon, Dec 02, 2024 chevron-right Does anyone else have MGUS? 823 Replies Sun, Dec 01, 2024 chevron-right See more discussions Show references Hoffman R, et al. Neutrophilic leukocytosis, neutropenia, monocytosis, and monocytopenia. In: Hematology: Basic Principles and Practice. 6th ed. Philadelphia, Pa.: Saunders Elsevier; 2013. http://www.clinicalkey.com. Accessed Feb. 1, 2017. Coates TD. Overview of neutropenia in children and adolescents. http://www.uptodate.com/home. Accessed Jan. 30, 2017. Coates TD. Approach to the patient with neutrophilia. http://www.uptodate.com/home. Accessed Feb. 1, 2017. Definition of white blood cell. National Cancer Institute. https://www.cancer.gov/publications/dictionaries/cancer-terms?cdrid=45993. Accessed Feb. 1, 2017. AskMayoExpert. Neutropenia. Rochester, Minn.: Mayo Foundation for Medical Education and Research; 2016. Lymphocytopenia. Merck Manual Professional Version. http://www.merckmanuals.com/professional/hematology-and-oncology/leukopenias/lymphocytopenia. Accessed Jan. 31, 2017. Monocytopenia. Merck Manual Professional Version. http://www.merckmanuals.com/professional/hematology-and-oncology/leukopenias/monocytopenia. Accessed Jan. 31, 2017. Adkinson NF, et al. Eosinophilia and eosinophil-related disorders. In: Middleton's Allergy: Principles and Practice. 8th ed. Philadelphia, Pa.: Saunders Elsevier; 2014. http://www.clinicalkey.com. Accessed Feb. 1, 2017. Adkinson NF, et al. Biology of basophils. In: Middleton's Allergy: Principles and Practice. 8th ed. Philadelphia, Pa.: Saunders Elsevier; 2014. http://www.clinicalkey.com. Accessed Feb. 1, 2017. Riggin EA. 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