Leukocytosis

Leukocytosis is an elevation of the white blood cell count (the leukocytecount) above the normal range. The normal adult human leukocyte count in peripheral bloodis 4.4-10.8 x 10⁹/L. A white blood count of 11.0 or more suggests leukocytosis.

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, and exposure to certain medications or chemicals. Leukocytosis can also be the first indication of neoplastic growth of leukocytes.

A leukocyte count above 25 to 30 x 10⁹/Lis termed a leukemoid reaction, which is the reaction of a healthy bone marrow to extreme stress, trauma, or infection. (It is different from leukemiaand from leukoerythroblastosis, in which immature blood cells are present in peripheral blood.)

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

Leukocytosis can be subcategorized by the type of white blood cell that is increased in number. Leukocytosis in which neutrophilcount is elevated is neutrophilia; leukocytosis in which lymphocytecount is elevated is lymphocytosis; leukocytosis in which monocytecount is elevated is monocytosis; and leukocytosis in which eosinophilcount is elevated is eosinophilia.

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It uses material from the http://en.wikipedia.org/wiki/Leukocytosis Wikipedia article Leukocytosis.