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Leukocytosis Definition

Leukocytosis is defined as a state in which there is increased leukocytes (WBC’s – White Blood Cells) count in the blood above the normal range with respect to age and sex. Leukocytes are also known by the name white blood cells or WBCs. These leukocytes are vital part of the immune system, enabling the individuals to fight infections. Leukocytes are being produced in the bone marrow, and after its production, it circulates in the blood for some time and leaves the blood for the functions to be carried out.

Leukocytosis Counts

Leukocyte count may increase when the bone marrow production increases or when the exit of WBCs from the blood is decreased. In adults, the normal leukocyte count is 11.0 x109/L leukocytes. Leukocytosis occurs when the count becomes 15,000-20,000 per microliter. Leukocytosis is a response to noxious stimulus that is part of an inflammatory reaction; it is usually accompanied by certain cytologic abnormalities like Dohle bodies or toxic granulation. Leukocyte count greater than 25 to 30 x 109/L is called as leukemoid reaction, exhibited by a healthy bone marrow when subjected to extreme trauma, stress and infection.

Leukocytosis Types

  1. Neutrophilia
  2. Monocytosis
  3. Basophilia
  4. Eosinophilia
  5. LymphocytosisLeukocytosis - High wbc count
Picture : Leukocytosis – High White Blood Cell count

Leukocytosis Classification

Leukocytosis is subcategorized on the basis of the type of WBC that increases.

1. Neutrophilia (neutrophil count is elevated)

According to the neutrophilia mechanism:-

  • Increased production
  • Demargination (decreased out passage from the vascular space)
  • Increased mobilization from the bone marrow storage pool
  • Decreased margination into the tissues

2. Monocytosis: monocyte count is elevated
3. Basophilia: basophil count is elevated
4. Eosinophilia: eosinophil count is elevated
5. Lymphocytosis: lymphocyte count is elevated

Leukocytosis With Left Shift

When the immature leukocytes proportion is greater than the mature leukocytes, it leads to leukocytosis. Various pathological tests conducted will diagnose leukocytosis with left shift. Whenever there is an increase in the leukocyte count, it always accompanies left shift leukocytosis. Leukocytes with left shift is not a disease; instead, it is an indication of a leukemoid reaction.

A left shift leukocytosis indicates that the immature leukocytes are greater than mature neutrophils. This may be due to C3a and GCSF inflammation in the precursor cells of bone marrow of a patient because of proliferation and abnormal increase in the monocyte and granulocyte precursors. It can be diagnosed by a complete blood count. A complete blood count will denote leukocytosis with left shift.

Leukocytosis Pathophysiology

Leukocytosis may be a response to several inflammations, infections or physiological processes like exercise or stress. This reaction is mediated by the released molecules in response to stimulations, including growth or survival factors like c-kit ligand, granulocyte-macrophage colony-stimulating factor, granulocyte colony-stimulating factor. Other stimulations include cytokines like interleukin-1, interleukin-3, interleukin-6, interleukin-8 and tumor necrosis factor; and adhesion molecules like CD11b/CD18.

These stimulatory events control the following mechanisms for determining the peripheral leukocyte count:-

  • Precursor cells and storage pool of lymphoid and myeloid cells
  • The rate at which cells release from the bone marrow’s storage pool
  • The rate of marginating cells passing out from the blood vessels to the tissues
  • Rate of cell loss in the tissues

Leukocytosis Symptoms

The symptoms are a result of the disease that led to leukocytosis.

  • Fever
  • Pain or tingling sensation in the arms, legs, or abdomen
  • Bleeding or bruising.
  • Feeling dizzy, sweaty or faint
  • Feeling weak, sick or tired.
  • Nausea
  • Trouble thinking or seeing.
  • Trouble breathing.
  • Poor appetite and unusual weight loss
  • Painful erection in males

Leukocytosis Causes


It can be caused by virus, bacteria or parasite

Eg: – Chicken pox, pneumonia, tuberculosis, bladder infections and sinusitis


It can be due to pain, swelling and redness in joints

Eg: – Arthritis


Like inflammatory bowel disease

Tissue damage

It can be caused in case the body tissues get damaged

Eg: – Burns, heart disease and cancer

Immune reactions

Here, the immune system reacts strongly

Eg: – Asthma or allergies

Bone marrow problems

Here, bone marrow makes many WBCs than needed, but does not function like normal WBCs.

Eg: – Leukemia or blood cancer, myelofibrosis, polycythemia vera, thrombocytopenia


Certain medicines used for treating mental health disorder, inflammation, breathing problems and cancer cause leukocytosis.

Eg: – corticosteroids, epinephrine (beta agonist) and lithium (psychotic drug)


Both emotional and physical (exercise)



Like splenectomy

Hemolytic anemia


Eg: – Thyrotoxicosis, Urinary tract infection, trauma, Worm infestation, Malignancy, Medication

Leukocytosis Diagnosis

  • Complete blood count (CBC)
  • Peripheral blood smear (PBS)
  • PBS shows the form and shape of WBCs
  • PBS shows the elevated WBC type
  • Bone marrow biopsy
  • History taking – To figure out the cause for leukocytosis

Leukocytosis Treatment

1. Intravenous fluids

To provide extra fluid to the blood vessels

2. Medication

  • Antibiotics

This is given to prevent or treat the infection causing leukocytosis.

  • Steroids

This is given for decreasing inflammation, which is causing leukocytosis.

  • Antacids

This is mainly given for decreasing the amount of acid present in the urine during treatment for leukocytosis.

  • Anti-uric acid

This is given for decreasing the uric acid amount in the body and to prevent further cell damage.

3. Leukocytoreduction

This procedure decreases the WBCs in blood, and stops the leukostasis formed when WBCs clump together in blood.

a. Leukapheresis

Through IV, blood is taken and the WBCs are removed from blood through a machine. The blood without white blood cells is injected back to the body. It can also be donated to another patient.

b. Chemotherapy

It is used for treating cancers like leukemia by killing the cancerous cells. It is used to decrease the amount of WBCs, as during chemotherapy healthy WBCs also get destroyed with the cancerous cells. It can also be used for shrinking the cancerous lymph nodes; once the tumor becomes smaller, surgery may be performed. Frequent blood tests may be needed to keep a track on the WBC count.

4. Bone marrow transplant (BMT)

Here, the healthy bone marrow replaces the diseased bone marrow. The bone marrow may be taken from a donor or the patient’s body (if the cancer is not in an active state). Bone marrow transplant can cure the illness, but may cause serious health problems, and also demands a long hospital stay.







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