Neutropenia is the condition of having abnormally few neutrophils present in the blood. The normal value is 1500-1800 neutrophils/microliter. Neutropenia is considered less than 1500/microliter. One of the characteristic features of neutropenia is the absence of pus. Pus is mostly made out of neutrophils, so someone who is lacking neutrophils is not going to make pus. One way of treating an individual who is suffering from neutropenia is by giving them granulocyte colony-stimulating factor (G-CSF) which stimulates the bone marrow to produce granulocytes like neutrophils.
There are several different types of neutropenia:
- Benign Ethnic Neutropenia is a condition observed in those of African descent in the absence of other causes for the neutropenia. It is an inherited condition that results in mild to moderate neutropenia. Interestingly, it is not generally associated with increased infections, so management of this condition is likely to be nothing more than counsel the patient to see further assessment if a pattern of recurrent or severe infections occur. The inherited gene in this condition is called the DARC gene which codes for a protein called the “Duffy” antigen. The Duffy antigen is a chemokine receptor that appears to have some role in neutrophil chemotaxis. A current line of thought is that a mutated Duffy antigen somehow contributes to a decrease in movement for neutrophils to leave the bone marrow and enter the circulation.
- Kostman Syndrome is an inherited bone marrow disorder that causes a lack of neutrophils. It is also known as severe congenital neutropenia (SCN). There are several possible mutations that can cause this syndrome, but as a general rule the result is an increase in the activation of apoptotic pathways that are triggered in the neutrophils. Neutrophils die at a much higher rate than normal and functional neutrophils in circulation can reach levels lower than 200/microliter. A neutrophil count this low makes it very hard to fight off infection and conditions such as ear infections, respiratory infections, skin infections, and gingivitis..
- Felty Syndrome is also known as “super rheumatoid disease”. It is characterized by the regular symptoms of rheumatoid arthritis with the addition of neutropenia and splenomegaly. Splenomegaly occurs because immune complexes get deposited in the spleen and cause the inflammation that results in spleen enlargement. The enlarged spleen can sequester a larger amount of neutrophils so when neutrophils get filtered through the spleen, more of them can get trapped and die. This entrapment and death contributes to the neutropenia found with Felty Syndrome.
- Other: While neutropenia can be caused by the diseases previously mentioned, it can also be caused by immune responses against neutrophils (some drugs act as haptens on neutrophils). Also, any condition that affects the bone marrow stem cells may cause neutropenia. If bone marrow is affected by radiation, chemotherapy, cancer, infections, or anything else then agranulocytosis may occur. Agranulocytosis is a condition which induces neutropenia as well as decreased concentrations of other granulocytes.