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| Leukocytosis | |
|---|---|
| Specialty | Infectious disease,pathology |
Leukocytosis is a condition in which the white cell (leukocyte) count is above the normal range in theblood.[1][2] It is frequently a sign of aninflammatory response,[3] most commonly the result ofinfection, but may also occur following certain parasitic infections orbone tumors as well asleukemia. It may also occur after strenuous exercise, convulsions such as epilepsy, emotional stress, pregnancy and labor, anesthesia, as a side effect of medication (e.g.,lithium), and epinephrine administration.[1] There are five principal types of leukocytosis:[4]
This increase in leukocyte (primarily neutrophils) is usually accompanied by a"left upper shift" in the ratio of immature to mature neutrophils and macrophages. The proportion of immature leukocytes increases due to proliferation and inhibition of granulocyte and monocyte precursors in the bone marrow which is stimulated by several products of inflammation including C3a and G-CSF.Although it may indicate illness, leukocytosis is considered a laboratory finding instead of a separatedisease. This classification is similar to that offever, which is also a test result instead of a disease.[citation needed]"Right shift" in the ratio of immature to matureneutrophils is considered with reduced count or lack of "young neutrophils" (metamyelocytes, andband neutrophils) inblood smear, associated with the presence of "giant neutrophils". This fact shows suppression of bone marrow activity, as a hematological sign specific forpernicious anemia andradiation sickness.[6]
A leukocyte count above 50 × 109/L is termed aleukemoid reaction, which is the reaction of a healthy bone marrow to extreme stress, trauma, or infection. It is different fromleukemia and fromleukoerythroblastosis, in which either immature white blood cells (acute leukemia) or mature, yet non-functional, white blood cells (chronic leukemia) are present in peripheral blood.[citation needed][7]
Leukocytosis can be subcategorized by the type of white blood cell that is increased in number. Leukocytosis in whichneutrophils are elevated isneutrophilia; leukocytosis in whichlymphocyte count is elevated islymphocytosis; leukocytosis in whichmonocyte count is elevated ismonocytosis; and leukocytosis in whicheosinophil count is elevated iseosinophilia.[8]
An extreme form of leukocytosis, in which the WBC count exceeds 100,000/μL, isleukostasis. In this form there are so many WBCs that clumps of them blockblood flow. This leads toischemic problems includingtransient ischemic attack andstroke.[citation needed]
| Causes of leukocytosis | ||||
|---|---|---|---|---|
| Neutrophilic leukocytosis (neutrophilia) | ||||
| Eosinophilic leukocytosis (eosinophilia) |
| |||
| Basophilic leukocytosis Basophilia | (rare)[8] | |||
| Monocytosis | ||||
| Lymphocytosis | ||||
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. For lung diseases such as pneumonia and tuberculosis, WBC count is very important for the diagnosis of the disease, as leukocytosis is usually present.[citation needed]
The mechanism that causes leukocytosis can be of several forms: an increased release of leukocytes frombone marrow storage pools, decreased margination of leukocytes onto vessel walls, decreasedextravasation of leukocytes from the vessels into tissues, or an increase in number of precursor cells in the marrow.[10]
Certain medications, includingcorticosteroids,lithium andbeta agonists, may cause leukocytosis.[11]
Leukocytosis is an expected finding in healthy women during the post-partum period and is not a cause for alarm unless accompanied by clinical manifestations of infection.[12]
Below areblood reference ranges for various types of leukocytes/WBCs.[13] The 97.5 percentile (right limits in intervals in image, showing 95%prediction intervals) is a common limit for defining leukocytosis.[citation needed]
While treatment is usually not necessary in the majority of cases, hyperleukocytosis (WBC count > 50 or 100 × 109/L), which can be seen in some leukemic patients, is treated to preventleukostasis.[14][15]