Neutrophils are white blood cells (WBC) that move from the blood into the cells to kill invading bacteria and fungi. If neutrophil levels become too high, neutrophilia results. Neutrophilia is the most common form of leukocytosis – a condition involving an increased number of leukocytes in the blood. Absolute neutrophilia refers to the increase in the total number of leukocytes in the blood as well as an increased percentage of neutrophils. This results in a neutrophil count of over 8,000.
Neutrophils are produced in the bone marrow, released into the blood, circulate briefly, and migrate into tissue spaces and onto epithelial surfaces.
There are many possible causes for an abnormally high neutrophil count. The most common and important cause of neutrophilia is infection, and most infections cause neutrophilia.
One basic cause of a high neutrophil count is when a high level of stress is placed on the body. The stress can due to many factors such as nervousness, exercise, or seizures (involuntary muscle movements due to overexcitement of nerve cells in the brain).
Corticosteroids, whether from stress or when using drugs like prednisone, cause increased bone marrow release of mature neutrophils, movement into the CNP, and decreased tissue migration. An increase in white blood cells and neutrophilia occurs 4 to 8 hours after elevation of stress hormones or steroid use and return to normal 1 to 3 days after later. Lymphopenia can occur concurrently.
Aside from those listed below, other causes include:
Inflammation stimulates bone marrow release of neutrophils to the site of inflammation. The time for production of new cells from the bone marrow is 4 to 6 days and neutrophils circulate for about 10 hours. Neutrophils move into tissues randomly and are destroyed in the spleen, liver, and bone marrow after performing their function.
Inflammation, necrosis, and immune-mediated disease can cause increased tissue demand and increased bone marrow release of neutrophils. Leukocytosis (at levels of 15,000 to 30,000), neutrophilia with a high neutrophils to lymphocytes ratio, toxic neutrophils, lymphopenia, eosinopenia, and variable monocytosis are seen often at the same time.
In a complete blood count (CBC) report, neutrophils may be referred to as polymorphonuclear cells (polys) or neutrophils. The absolute neutrophil count (ANC) is a measure of the total number of neutrophils present in the blood. The normal range for the neutrophil count is 1,500 to 8,000 cells per cubic mm. The ANC can be calculated by multiplying the total WBC by the percent of neutrophils.
Neutrophilia is defined as an increase in circulating neutrophils in the peripheral blood. The absolute neutrophil count (ANC) defines neutrophilia. ANC is found by multiplying the percentage of bands and neutrophils on a differential by the total white blood cell count. An abnormal ANC is more than 8,000 cells per cubic mm.
Primary myelofibrosis is a myeloproliferative disorder that causes proliferation of bone marrow cells.
Essential thrombocythemia is a myeloproliferative disorder that causes proliferation of bone marrow cells.
Polycythemia vera is a myeloproliferative disorder that causes proliferation of bone marrow cells.
Loss of blood cells through excessive bleeding can cause neutrophilia.
Inflammation, sepsis, necrosis, and immune-mediated disease can cause increased tissue demand and increased bone marrow release of neutrophils.
Rheumatoid arthritis and other inflammatory diseases can cause neutrophilia.
Chronic myelocytic leukemia is a myeloproliferative disorder that causes proliferation of bone marrow cells.
Certain medications such as corticosteroids or lithium carbonate can cause neutrophilia.
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