Leukocytosis



Synonyms and keywords: Granulocytosis, neutrophilia

Overview
Leukocytosis is an elevation of the white blood cell count (the leukocyte count) above the normal range. The normal adult human leukocyte count in peripheral blood is 4.4-10.8 x 109/L. A white blood count of 11.0 x 109/L or more suggests leukocytosis. Often, the word refers to an increased neutrophil granulocyte count, as neutrophils are the main granulocytes. An increase in eosinophil granulocyte is known as eosinophilia. Granulocytosis can be a feature of a number of disease processes including infection, especially bacteria; malignancy, most notably leukemia (it is the main feature of chronic myelogenous leukemia, CML) and autoimmune disease. Although it may be a sign of illness, leukocytosis in-and-of itself is not a disorder, nor is it a disease. It is simply a laboratory finding.

Epidemiology and Demographics
Leukocytosis is very common in acutely ill patients. It occurs in response to a wide variety of conditions, including viral, bacterial, fungal, or parasitic infection, cancer, hemorrhage, and exposure to certain medications or chemicals including steroids. Leukocytosis can also be the first indication of neoplastic growth of leukocytes.

Pathophysiology
The mechanism that causes leukocytosis can be of several forms: an increased release of leukocytes from bone marrow storage pools, decreased margination of leukocytes onto vessel walls, decreased extravasation of leukocytes from the vessels into tissues, or an increase in number of precursor cells in the marrow.

Classification Scheme
Leukocytosis can be subcategorized by the type of white blood cell that is increased in number.

Granulocytosis / Neutrophilia
Granulocytosis or neutrophilia is a subcategory of leukocytosis in which neutrophil count is elevated.

For complete list of conditions that cause neutrophilia, click here

Eosinophilia
Eosinophilia is a subcategory of leukocytosis in which eosinophil count is elevated.

For complete list of conditions that cause eosinophilia, click here

Monocytosis
Monocytosis is a subcategory of leukocytosis in which monocyte count is elevated.

For complete list of conditions that cause monocytosis, click here

Basophilia
Basophilia is a subcategory of leukocytosis in which basophilia count is elevated.

For complete list of conditions that cause basophilia, click here

Lymphocytosis
Lymphocytosis is a subcategory of leukocytosis in which lymphocyte count is elevated.

For complete list of conditions that cause neutrophilia, click here

Leukemoid Reaction
A leukocyte count of above 25 to 30 x 109/L is termed as leukemoid reaction. This occurs as a reaction of healthy bone marrow to extreme stress, trauma, or infection.

Leukemoid reaction is different from leukemia and from leukoerythroblastosis, in which immature blood cells are present in peripheral blood.

By Organ System
===In alphabetical order ===
 * Colonic diverticulitis
 * Hepatosplenic T-cell lymphoma
 * Interleukin 1 receptor antagonist deficiency
 * Neuroleptic malignant syndrome
 * Plerixafor

Related Chapters

 * Granulocytosis
 * Neutrophilia
 * Eosinophilia
 * Monocytosis
 * Lymphocytosis
 * Basophilia