Definition

Neutropenia is an abnormally low level of neutrophils in the blood. Neutrophils are white blood cells (WBCs) produced in the bone marrow that ingest bacteria. Neutropenia is sometimes called agranulocytosis or granulocytopenia because neutrophils make up about 60% of WBCs and have granules inside their cell walls. Neutropenia is a serious disorder because it makes the body vulnerable to bacterial and fungal infections.

  Description

The normal level of neutrophils in human blood varies slightly by age and race. Infants have lower counts than older children and adults, and African Americans have lower counts than Caucasians or Asians. The average adult level is 1500 cells/mm³ of blood. Neutrophil counts (in cells/mm³) are interpreted as follows:

• greater than 1000. Normal protection against infection.
• 500-1000. Some increased risk of infection.
• 200-500. Great risk of severe infection.
• lower than 200. Risk of overwhelming infection; requires hospital treatment with antibiotics.

  Causes and symptoms

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:

• medications that affect the bone marrow, including cancer drugs, chloramphenicol (Chloromycetin), anticonvulsant medications, and antipsychotic drugs (Thorazine, Prolixin, and other phenothiazines)
• hereditary and congenital disorders that affect the bone marrow, including familial neutropenia, cyclic neutropenia, and infantile agranulocytosis
• cancer, including certain types of leukemia
• radiation therapy
• exposure to pesticides
• vitamin B₁₂ and folate (folic acid) deficiency

DESTRUCTION OF WBCS

WBCs are used up at a faster rate by:

• 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

Symptoms

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

Diagnosis is made on the basis of a white blood cell count and differential. The cause of neutropenia is often difficult to establish and depends on a combination of the patient's history, genetic evaluation, bone marrow biopsy, and repeated measurements of the WBC.

  Treatment

Treatment of neutropenia depends on the underlying cause.

Medications

Patients with fever and other signs of infection are treated for seven to 10 days with antibiotics. Nutritional deficiencies are corrected by green vegetables to supply folic acid, and by vitamin B supplements.

Medications known to cause neutropenia are stopped. Neutropenia related to pesticide exposure is treated by removing the patient from the contaminated environment.

Patients receiving chemotherapy for cancer may be given a blood growth factor called sargramostim (Leukine, Prokine) to stimulate WBC production.

Surgery

Patients with Felty's syndrome who have repeated infections may have their spleens removed.

  Prognosis

The prognosis for mild or chronic neutropenia is excellent. Recovery from acute neutropenia depends on the severity of the patient's infection and the promptness of treatment.

   Key Terms:

Cyclical neutropenia A rare genetic blood disorder in which the patient's neutrophil level drops below 500/mm for six to eight days every three weeks. Differential A blood cell count in which the percentages of cell types are calculated as well as the total number of cells. Felty's syndrome An autoimmune disorder in which neutropenia is associated with rheumatoid arthritis and an enlarged spleen. Granulocyte Any of several types of white blood cells that have granules in their cell substance. Neutrophils are the most common type of granulocyte. Neutrophil A granular white blood cell that ingests bacteria, dead tissue cells, and foreign matter. Sargramostim A medication made from yeast that stimulates WBC production. It is sold under the trade names Leukine and Prokine. Sequestration and margination The removal of neutrophils from circulating blood by cell changes that trap them in the lungs and spleen.

   Resources:

Books

• Baehner, Robert L. "Neutropenia." In Conn's Current Therapy, 1996, ed. Robert E. Rakel. Philadelphia: W. B. Saunders Co., 1996.
• "Hematology and Oncology: Leukopenia; Neutropenia." In The Merck Manual of Diagnosis and Therapy. 16th ed. Ed. Robert Berkow. Rahway, NJ: Merck Research Laboratories, 1992.
• "Infectious Diseases: Neonatal Sepsis." In Neonatology: Management, Procedures, On-Call Problems, Diseases and Drugs, ed. Tricia Lacy Gomella, et al. Norwalk, CT: Appleton & Lange, 1994.
• Lane, Peter A., et al. "Hematologic Disorders." In Current Pediatric Diagnosis & Treatment, ed. William W. Hay Jr., et al. Stamford: Appleton & Lange, 1997.
• Linker, Charles A. "Blood." In Current Medical Diagnosis and Treatment, 1998. 37th ed. Ed. Stephen McPhee, et al. Stamford: Appleton & Lange, 1997.
• Pearson, Starr P., and Stanley J. Russin. "Quantitative Disorders of Granulocytes." In Current Diagnosis. Vol. 9. Ed. Rex B. Conn, et al. Philadelphia: W. B. Saunders Co., 1997.
• Physicians' Guide to Rare Diseases. Ed. Jess G. Thoene. Montvale, NJ: Dowden Publishing Co., Inc., 1995.