• Leucocytosis is when the white blood cell count (WBC) is above the normal.
  • Leukocytosis is usually an indicator of an underlying inflammatory, infectious, or neoplastic process.

Blood is made of blood cells floating and plasma is the liquid part of the blood and is mostly water but also contains proteins hormones minerals and vitamins. there are 3 types of blood cells in the blood, red blood cells are also called erythrocytes or red blood cells that carry oxygen to cells and tissues; platelets are small cells that help the blood to clot; white blood cells, the body soldiers, that fight infection, and repair tissue. Leucocytosis is when the white blood cell count (WBC) is above the normal.


White blood cells are the general term for the 5 types of white blood cells: Neutrophils, lymphocytes, eosinophils, basophils, monocytes.

  • Neutrophils: These make up 50-70%of total white blood cells. They help fight off fungal and bacterial infections.  They are also involved in the healing processes
  • Lymphocytes: These are the second most common type of white blood cell. They protect the body from viral infections and cancer cells
  • Basophils: These are the least common type of the white blood cells. They are involved in inflammatory reactions to allergens.
  • Monocytes: These are the largest of the white blood cells. They play a role in fighting off bacteria, fungi, and viruses. They also help repair tissue that has been damaged by inflammation. They are also important finding tumor cells
  • Eosinophils: These fight parasites and play a role in allergic reactions and conditions, such as asthma and eczema.


How is a leukocytosis diagnosed?

The diagnosis of leukocytosis is commonly done through a complete blood cell count or CBC or a Leukogram.  The normal white blood cell count in the blood is between 3,500 and 11,000 white blood cells.  If the count is under 3500, the term leukopenia is used.  If it is above 11,000, the term leukocytosis is used.

The bone marrow which is the tissue that is inside the bone is responsible for producing white blood cells.  As these, bone marrow immature white blood cells develop, they form 5 different types of white blood cells.  Each of these types of cells has a special function and are the immunoprotective army that is available and ready to fight in our system.

 Like most blood disorders, a thorough physical examination and medical history are essential.

–Complete blood cell count (CBC) with differential: A sample of blood is drawn and analyzed for the number of red blood cells and platelets, number and type of white blood cells, amount of hemoglobin and the red blood cells, and the portion of the blood sample made up of red blood cells.  In addition, from this CBC a peripheral blood smear is made to study the morphology of the number and types of white blood cells. In addition; check for the presence of blast cells.

–Blood chemistry studies: In this procedure blood sample is taken to measure the number of certain substances released into the blood by organs and tissues in the body.

–Bone marrow aspiration and biopsy: in this procedure, a hollow needle is inserted In the hip or breast bone, and bone marrow, blood and a small piece of bone are removed.  This  is examined  by a pathologist under a microscope to look for abnormal cells,

The same sample it is normally used for flow cytometry, fluorescent in situ hybridization, cytogenetics, and gene mutation test; the mutations currently tests are Jak 2, MPL, and CALR.

The term left shift is a >5% increase in the percentage of immature precursors (primarily bands) due to the rapid release of the bone marrow reserve. The shift to the left may be so marked as to suggest myeloid leukemia. 

Monocytosis is defined as an absolute monocyte count of >500–800/mm3. The causes of basophilia, defined as an absolute basophil count >200/mm3.

Leukemoid reaction is defined as an extremely elevated WBC (>30 x1000 cells/uL) in conjunction with a left-shift. A left shift signifies that there are immature white blood cells.

What are the causes of Leukocytosis?

The two most familiar diagnostic categories are infections or primary hematologic disease. Infection is often self-evident after a thorough history and physical examination. Note that some severe infections can result in extremely high WBCs.

Leukocytosis causes

Hematologic causes of leukocytosis include acute or chronic leukemias and myeloproliferative diseases. Typically, leukocytosis is not seen in myelodysplastic syndrome (MDS) unless MDS is transforming into acute leukemia or the MDS overlaps with a myeloproliferative syndrome. Myeloproliferative diseases include chronic myelogenous leukemia (CML), polycythemia vera, essential thrombocythemia, and primary myelofibrosis (previously known as myelofibrosis with myeloid metaplasia). Although CML typically elevates the WBC, polycythemia vera elevates the red blood cell count, and essential thrombocythemia raises the platelet count, all four myeloproliferative diseases overlap and each often results in a leukocytosis (less commonly with essential thrombocythemia).


In addition to infection and primary hematologic disease, the following other causes can lead to leukocytosis: Trauma and burns can cause a high WBC, sometimes very high (leukemoid reaction), as can non-hematologic neoplasms such as pancreatic cancer. Certain therapeutic drugs lead to leukocytosis. These include filgrastim (G-CSF, granulocyte-colony stimulating factor), sargramostim (GM-CSF, granulocyte-macrophage colony stimulating factor), corticosteroids, epinephrine, beta-agonists, and notably lithium (while other psychiatric medications can cause neutropenia). Other autoimmune and inflammatory diseases, such as rheumatoid arthritis, inflammatory bowel disease, and pancreatitis, can cause a leukocytosis (or neutropenia).

Common causes, yet often forgotten, including smoking, exercise, pregnancy, and other types of stress. These frequently increase a WBC by 25%. However, that 25% increase usually does not surpass the WBC upper limit of normal. So keep in mind these causes result in only a mild leukocytosis when present.

Leukocytosis is usually an indicator of an underlying inflammatory, infectious, or neoplastic process. Although lymphocytosis is most often associated with chronic lymphatic leukemia, neutrophilia or monocytosis of modest degree is most frequently associated with inflammation or infection. Marked elevation in the neutrophil and monocyte count raises the possibility of chronic leukemia. Moderate leukocytosis, involving mature white cells, carries no significant increase in perioperative risk. In most situations, leukocytosis requires no specific therapy except that of the underlying disorder. If the leukocytosis is related to the effects of leukemia, obviously the underlying illness and its therapy are of paramount importance in determining the perioperative risk.


How is Leukocytosis treated?

Treatment for Leukocytosis is directed at alleviating symptoms and targeting the infections and treating them at the earliest. Treatment for leukopenia is usually palliative.

In most cases, treatment for leukocytosis is not necessary. In extreme instances of hyperleukocytosis syndrome (eg, acute leukemia), leukapheresis, hydration, and urine alkalinization to facilitate uric acid excretion are indicated; however, perform these treatments only in consultation with a hematologist, oncologist, or both. Direct treatment towards the underlying etiology.

Leukemic hyperleukocytosis may cause clinically significant complications when the WBC count exceeds 100,000/μL in acute myelogenous leukemia and 300,000/μL in acute lymphoblastic leukemia. Therefore, in patients with these findings, measures to reduce the WBC count are advisable. However, a decrease in leukocyte count that is too rapid carries a risk of severe tumor lysis syndrome and should be avoided.

Leukopheresis or exchange blood transfusion is a treatment of choice for this purpose, with hydration, urine alkalinization, and administration of allopurinol or rasburicase (uric acid oxidase) to reduce serum uric acid and minimize tumor lysis syndrome. When rasburicase is used, urine alkalinization is not recommended.



The information in this document does not replace a medical consultation. It is for personal guidance use only. We recommend that patients ask their doctors about what tests or types of treatments are needed for their type and stage of the disease.


American Cancer Society

The National Cancer Institute

National Comprehensive Cancer Network

American Academy of Gastroenterology

National Institute of Health

MD Anderson Cancer Center

Memorial Sloan Kettering Cancer Center

American Academy of Hematology


© Copyright 2018 - Hematology Oncology Care. Digital Marketing by MD Digitas