Neutropenia

Neutropenia is "a decrease in the number of neutrophilic leukocytes in the blood." It is a subset of leukopenia and its subset granulocytopenia. The Absolute Neutrophil Count (ANC) is used to define levels of neutropenia; it can be calculated from components of the complete blood count or directly measured by some blood analyzers.

The half-life of a neutrophil is less than one-half of a day.

Diagnosis

Rather by definition, the diagnosis is a laboratory determination, although history and physical may help establish the cause. Since the routine complete blood count allows computation or measurement of neutrophils, neutropenia may come up on routine screening.

Guidelines

There are three general guidelines used to classify the severity of neutropenia based on the absolute neutrophil count (ANC) measured in cells per microliter of blood, and reported as a count:

• Mild neutropenia (1000 < ANC < 1500) — minimal risk of infection
• Moderate neutropenia (500 < ANC < 1000) — moderate risk of infection
• Severe neutropenia (ANC < 500) — severe risk of infection.

There is variation for ethnicity. When they are available, it is desirable to state predictors and ranges in terms of genetic markers rather than the more imprecise race. Subsequent work indicates that the race-related generic abnormality is the "Duffy antigen receptor for chemokine (DARC), which is associated with the ethnic group to which individuals belong. The single-nucleotide polymorphism strongly associated with race is DARC rs2814778."

Neutropenia is more commonly found in women and the elderly. Benign ethnic neutropenia has been observed in Africans, African-Caribbean persons, West Indians Ethiopians, Yemenite Jews and certainArabs.

Grading

A more formal grading system is:

• Grade 1: < 2.0 x 10⁹/L (< 2000/mm³) and > 1.1 x 10⁹/L (> 1500/mm³)
• Grade 2: < 1.5 x 10⁹/L (< 1500/mm³) and > 1.0 x 10⁹/L (> 1000/mm³)
• Grade 3: < 1.0 x 10⁹/L (< 1000/mm³) and > 0.5 x 10⁹/L (> 500/mm³)
• Grade 4: < 0.5 x 10⁹/L (< 500/mm³

Differential diagnosis

There are many causes of neutropenia. Some causes are caused by infections while others are not. Some causes of neutropenia may include Acquired Immune Deficiency Syndrome (AIDS), influenza, typhus, malaria, tuberculosis, dengue, Rickettsial infections, systemic lupus erythematosus, Sjogren’s syndrome, Felty’s syndrome, Kostmann syndrome, enlargement of the spleen, folate deficiencies and sepsis.

Idiopathic and secondary neutropenias

Idiopathic neutropenia

Idiopathic neutropenia includes many types of neutropenia and can happen at any point in life for unknown reasons. It can occur in both adults and children and the effects are variable based on disease severity. As with any classification of "idiopathic" disease, there is an implication that common causes have been ruled out.

Autoimmune neutropenia

Autoimmune neutropenia is found in children between six months and four-years-old that have not been diagnosed with congenital neutropenia. This is the most common cause of neutropenia for children in this age group. Severe bacterial infections are rare. Autoimmune neutropenia may also be found in adults, who are usually between the ages of 20 to 40, and most commonly women. This condition is usually associated with other medical conditions.

Drug-induced neutropenia

Other medical conditions or medicines may cause neutropenia. Cancer patients undergoing chemotherapy could develop neutropenia.

Febrile neutropenia

Clinical practice guidelines define febrile neutropenia as "a single oral temperature of >=38.3°C (101°F) or a temperature of >=38.0°C (100.4°F) for >= 1 h. Neutropenia is defined as a neutrophil count of <500 cells/mm3, or a count of <1000 cells/mm3 with a predicted decrease to <500 cells/mm3"

A clinical prediction rule can estimate the risk of morbidity in the febrile patient with neutropenia. A score of >=21 indicates low risk.

Congenital neutropenia with associated immune defects

• Neutropenia with abnormal immunoglobulins: This disorder is observed in individuals with X-linked agammaglobulinemia, isolated immunoglobulin A (IgA) deficiency, X-linked hyperimmunoglobulin M (XHIGM) syndrome, and dysgammaglobulinemia type I. In XHIGM, which is due to mutations in the CD40 ligand, patients can actually have normal or elevated levels of IgM but markedly decreased serum IgG levels.
• Reticular dysgenesis: Patients demonstrate severe neutropenia, no cell-mediated immunity. agammaglobulinemia, and lymphopenia. Life-threatening infections occur that are refractory to granulocyte colony-stimulating factor (G-CSF).10,11,2 Bone marrow transplantation is the treatment of choice.

Primary inherited neutropenias

Kostmann Syndrome, cyclic neutropenia, idiopathic neutropenia and autoimmune neutropenia are considered rare medical disorders of the blood. Patients may register with the Severe Chronic Neutropenia Registry (SCNIR) founded in 1994 to monitor the clinical course, treatment and disease outcomes of registered patients.

The following information is from SCNIR

Kostmann syndrome

Kostmann syndrome, known as congenital neutropenia, is rare neutropenia found at birth. It is an inherited disease and can affect more than one family member. It is an inherited disease and therefore, more than one family member can be affected, but sporadic occurrence with only one patient in a family may occur. There is no prenatal testing available to check for Kostmann Syndrome. Children affected by Kostmann Syndrome are usually severe and children may have no neutrophils present in the blood. Neutrophils typically are in an arrested state of development or maturation arrest in the bone marrow. The neutrophils rarely mature to full stage development leaving the patient incapable of fighting off infection. Diagnosis is usually made during infancy.

Cyclic neutropenia

Cyclic neutropenia also is inherited. Neutrophil activity runs in cycles, typically 21 days, and range from normal blood counts to low blood counts. It is common for the ANC to drop to less than 200 cells/µl) (0.2 x 109/l). Common symptoms during the low period of the cycle may include mouth ulcers and inflammation. Severe infections such as otitis media (ear infections), pneumonia and bacteraemia (bacterial blood infections) are less likely to be seen.

“Cyclic neutropenia occurs because of fluctuating rates of cell production by the bone marrow stem cells”

Prevention

Hematopoietic colony-stimulating factors for primary prevention of febrile neutropenia may not decrease mortality but do decrease infections in patients undergoing cancer chemotherapy or stem cell transplantation according to a systematic review.

Granulocyte colony-stimulating factor is indicated in selected settings if the projected chance of febrile neutropenia is at least 20%.

Treatment

If neutropenia is secondary to another disease or external chemical, that disorder must be treated. When there is both neutropenia and immunoglobulin deficiency, the infection risk is high, and the treatment is intravenous immunoglobulin (IVIG).

Granulocyte colony-stimulating factor can be a potent treatment for severe neutropenia, but it is expensive and not without risk.

Determining Absolute Neutrophil Count (ANC)

Neutropenia is a subset of a leukopenia.Leukopenia means a low white blood cell count while neutropenia represents a lowered neutrophil count. Neutropenia has many causes and can be temporary. Absolute Neutrophil Count (ANC) is determined by using the results of your blood test, normally the differential white blood cell count (WBC). Neutrophils make up 50 to 70 percent of the white blood cell count. To determine your ANC use the following formula:

(% of neutrophils + % of bands) X WBC count = ANC.

Note: Neutrophils are sometimes called “segs” or “polys” while young while blood cells are referred to as bands.

An example of this formula at work is illustrated here:

If the WBC is 1,000 and the percentage of neutrophils is 70 percent, and there are no young white blood cells (bands) present, the ANC would be 700, according to the American Cancer Society.