Agranulocytosis is a blood abnormality characterized by the disappearance of a subclass of leukocytes: neutrophilic granulocytes. Given their importance in the immune system, their disappearance requires rapid medical treatment.

Agranulocytosis is a medical term used to refer to a blood abnormality. It corresponds to the almost total disappearance of blood neutrophil granulocytes, formerly known as blood neutrophils.

These blood components are a subclass of leukocytes (white blood cells), blood cells involved in the immune system. This subclass also represents the majority of leukocytes present in the blood. In the bloodstream, neutrophil granulocytes play a very important role because they are responsible for the defense against foreign bodies and infected cells. They are able to phagocyte these particles, that is to say to absorb them in order to destroy them.

Agranulocytosis is a blood abnormality that can be identified with a hemogram, also called Blood Count and Formula (NFS). This test provides a lot of information about blood cells. The blood count makes it possible in particular to quantify the various elements of the blood, of which the neutrophil granulocytes are part.

During the’neutrophil analysis, an abnormality is observed when the concentration of these cells is less than 1700 / mm3, or 1,7 g / L in the blood. If the level of neutrophilic granulocytes is too low, we speak of a neutropenia.

Agranulocytosis is a serious form of neutropenia. It is characterized by a very low level of neutrophilic granulocytes, less than 500 / mm3, or 0,5 g / L.

In most cases, agranulocytosis is a blood abnormality that occurs after taking certain drug treatments. Depending on the origin and characteristics of the anomaly, there are generally two types of drug agranulocytosis:

• acute drug-induced agranulocytosis, the development of which is due to the selective toxicity of a drug, which affects only the granulocyte line;
• drug-induced agranulocytosis in the context of aplastic anemia, the development of which is due to a disorder in the bone marrow, which are characterized by a depletion of several blood cell lines.

In the context of aplastic anemia, it is also possible to distinguish several types of agranulocytosis. Indeed, this blood disease characterized by an interruption in the production of blood cells in the bone marrow can have several origins. Aplastic anemia can be considered as:

• post-chemotherapy aplastic anemia when following chemotherapy treatment;
• accidental aplastic anemia when caused by certain drugs.

While drug-induced agranulocytosis represents between 64 and 83% of cases, these abnormalities may have other causes. Of bacterial, viral or parasitic origin, an infection at an advanced stage can in particular cause a depletion of neutrophilic granulocytes.

Given the role of neutrophilic granuclocytes in the immune system, agranulocytosis exposes the organism to a significant risk of infection. Neutrophils are no longer numerous enough to oppose the development of certain pathogens, which can lead to a septicemia, or sepsis, a generalized infection or inflammation of the body.

The symptoms of agranulocytosis are those of an infection. It can manifest itself by infectious signs in several regions of the body including the digestive system, the ENT sphere, the pulmonary system or even the skin.

Acute drug-induced agranulocytosis appears suddenly and is manifested by an outbreak of high fever (over 38,5 ° C) accompanied by chills. In bone marrow aplasia, the development of agranulocytosis may be gradual.

Agranulocytosis is a blood abnormality that needs to be treated quickly to avoid complications. Although treatment may vary depending on the origin of agranulocytosis, its management is generally based on:

• isolation in hospital to protect the patient;
• initiation of antibiotic therapy to treat infections;
• the use of granulocyte growth factors to stimulate the production of neutrophilic granulocytes.