Neutropenia

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Neutropenia

Neutropenia (adjective neutropenic), from Latin prefix neutro- and Greek suffix -πενία (deficiency) is a hematological disorder characterized by an abnormally low number of a type of white blood cell called a neutrophil. Neutrophils usually make up 50-70% of circulating white blood cells and serve as the primary defense against infections by destroying bacteria in the blood. Hence, patients with neutropenia are more susceptible to bacterial infections and, without prompt medical attention, the condition may become life-threatening (neutropenic sepsis).

Neutropenia can be acute or chronic depending on the duration of the illness. A patient has chronic neutropenia if the condition lasts for longer than 3 months. It is sometimes used interchangeably with the term leukopenia ("deficit in the number of white blood cells"), as neutrophils are the most abundant leukocytes, but neutropenia is more properly considered a subset of leukopenia as a whole.

There are numerous causes of neutropenia that can roughly be divided between either problems in the production of the cells by the bone marrow and destruction of the cells elsewhere in the body. Treatment depends on the nature of the cause, and emphasis is placed on the prevention and treatment of infection.

Classification

There are 3 general guidelines used to classify the severity of neutropenia based on the absolute neutrophil count (ANC) measured in cells per microliter of blood:

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.

The abovementioned ranges were developed in Caucasians. In blacks, mild neutropenia is a normal phenomenon, and neutropenia in this population is more properly defined as ANC < 1200. Higher cutoffs may lead to overdiagnosis of neutropenia in the black population.

Signs and symptoms

Neutropenia can go undetected, but is generally discovered when a patient has developed severe infections or sepsis. Some common infections can take an unexpected course in neutropenic patients; formation of pus, for example, can be notably absent, as this requires circulating neutrophil granulocytes.

Some common symptoms of neutropenia include:

Fever
Frequent infections due to lessened ability to fight bacterial infections
Mouth ulcers
Diarrhea
Burning sensation when urinating
Unusual redness, pain, or swelling around a wound
Sore throat
Shortness of breath
Shaking chills

Diagnosis

Low neutrophil counts are detected on a full blood count. Generally, some other investigations are required to arrive at the right diagnosis. When the diagnosis is uncertain, or serious causes are suspected, bone marrow biopsy is often necessary.

Other investigations commonly performed: serial neutrophil counts for suspected cyclic neutropenia, tests for antineutrophil antibodies, autoantibody screen and investigations for systemic lupus erythematosus, vitamin B12 and folate assays and acidified serum (Ham's) test.

Causes

Causes can be divided into the following groups:

Decreased production in the bone marrow:

aplastic anemia
cancer, particularly blood cancers
certain medications
hereditary disorders (e.g. congenital neutropenia, cyclic neutropenia)
radiation
Vitamin B₁₂ or folate deficiency.

Increased destruction:

autoimmune neutropenia.
chemotherapy treatments, such as for cancer and autoimmune diseases

Marginalisation and sequestration:

Hemodialysis

There is often a mild neutropenia in viral infections.

Therapy

There is no ideal therapy for neutropenia, but recombinant G-CSF (granulocyte-colony stimulating factor) can be effective in chemotherapy patients, in patients with congenital forms of neutropenia including severe congenital neutropenia, autosomal recessive Kostmann's syndrome, cyclic neutropenia, and myelokathexis.