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.
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).
Corticosteriods, 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, 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.
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.
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.