), 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.
There are 3 general guidelines used to classify the severity of neutropenia based on the absolute neutrophil count (ANC) measured in cells per microliter
- 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
. 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:
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 can be divided into the following groups:
- Decreased production in the bone marrow:
- Increased destruction:
- Marginalisation and sequestration:
There is often a mild neutropenia in viral infections.
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.
The relationship between a low neutrophil count and increased risk of infection was first demonstrated in patients with leukemia.