Neutropenia Health Article

Description

Neutropenia is an abnormally low level of neutrophils in the blood. Neutrophils are white blood cells (WBCs) produced in the bone marrow and comprise approximately 60% of the blood. These cells are critically important to an immune response and migrate from the blood to tissues during an infection. They ingest and destroy particles and germs. Germs are microorganisms such as bacteria, protozoa, viruses, and fungus that cause disease. Neutropenia is an especially serious disorder for cancer patients who may have reduced immune functions because it makes the body vulnerable to bacterial and fungal infections. White blood cells are especially sensitive to chemotherapy. The number of cells killed during radiation therapy depends upon the dose and frequency of radiation, and how much of the body is irradiated.

Neutrophils can be segmented (segs, polys, or PMNs) or banded (bands) which are newly developed, immature neutrophils. If there is an increase in new neutrophils (bands) this may indicate that an infection is present and the body is attempting a defense. Neutropenia is sometimes called agranulocytosis or granulocytopenia because neutrophils display characteristic multi-lobed structures and granules in stained blood smears.

The normal level of neutrophils in human blood varies slightly by age and race. Infants have lower counts than older children and adults. African-Americans have lower counts than Caucasians or Asians. The average adult level is 1, 500 cells/mm ³ of blood. Neutrophil counts (in cells/mm ³) are interpreted as follows:

• Greater than 1, 000. Normal protection against infection.
• 500-1, 000. Some increased risk of infection.
• 200-500. Great risk of severe infection.
• Lower than 200. Risk of overwhelming infection; requires hospital treatment with antibiotics.

Neutropenia has no specific symptoms except the severity of the patient's current infection. In severe neutropenia, the patient is likely to develop periodontal disease, oral and rectal ulcers, fever, and bacterial pneumonia. Fever recurring every 19-30 days suggests cyclical neutropenia.

Diagnosis is made on the basis of a white blood cell count and differential. The cause of neutropenia can be difficult to establish and depends on a combination of the patient's history, genetic evaluation, bone marrow biopsy, and repeated measurements of the WBC. However, in cancer patients it is usually an expected side effect of chemotherapy or radiation. The overall risk of infection is dependent upon the type of cancer an individual has as well as the treatment received. Patients at greater risk include those with hematologic malignancies, leukemia/lymphoma (cancers) and those who receive bone marrow transplants.

It is important to detect infections early. Some signs that indicate infection include:

• coughing and difficulty breathing, congestion
• an oral temperature greater than 105° with typical fever symptoms of chills and sweating
• problems in the mouth such as white patches, sore and swollen gums
• changes in urination or in stools
• drainage and pain from any cuts or tubes used in the cancer treatments such as catheters and feeding tubes
• an overall feeling of illness

Causes

Neutropenia may result from three processes:

Decreased WBC production

Lowered production of white blood cells is the most common cause of neutropenia. It can result from:

• Cancer, including certain types of leukemia.
• Radiation therapy.
• Medications that affect the bone marrow, including cancer drugs (chemotherapy), chloramphenicol (Chloromycetin), anticonvulsant medications, and antipsychotic drugs (Thorazine, Prolixin, and other phenothiazines). In hematopoietic stem cell transplantation (HSCT), high levels of total body irradiation (TBI) or chemotherapy are used to kill cancer cells, or these treatments may be combined. Two types of HSCT treatments are bone marrow transplantation (BMT) and peripheral blood stem cell transplantation (PBSCT). During the treatment process, the patient's normal bone marrow stem cells are killed along with the cancer cells. The stem cells are not able to mature into immune cells such as neutrophils, causing neutropenia. To reduce neutropenia, the normal stem cells from the patient may be removed prior to treatment and given back at a later time. Cells can also be supplied from another donor.
• Hereditary and congenital disorders that affect the bone marrow, including familial neutropenia, cyclic neutropenia, and infantile agranulocytosis.
• Exposure to pesticides.
• Vitamin B ₁₂ and folate (folic acid) deficiency.

Destruction of White Blood Cells

WBCs are used and die at a faster rate due to:

• acute bacterial infections in adults
• infections in newborns
• certain autoimmune disorders, including systemic lupus erythematosus (SLE)
• penicillin, phenytoin (Dilantin), and sulfonamide medications (Benemid, Bactrim, Gantanol)

Sequestration and margination of WBCs

Sequestration and margination are processes in which neutrophils are removed from the general blood circulation and redistributed within the body. These processes can occur because of:

• hemodialysis
• Felty's syndrome, or malaria. The neutrophils accumulate in the spleen.
• Bacterial infections. The neutrophils remain in the infected tissues without returning to the bloodstream.