Neutropenia classification
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Classification
There are 3 general guidelines used to classify the severity of neutropenia based on the absolute neutrophil count (ANC) measured in cells permicroliter 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.
NOTE: These are ranges for Caucasians. Neutropenia in black individuals is defined as ANC < 1200. This is a not well known fact that results in overdiagnosis of neutropenia in black population.[1]
Severe chronic neutropenia may be present at birth (congenital neutropenia) or may occur at any stage in life (acquired neutropenia). There are several types of severe chronic neutropenia:
Severe congenital neutropenia — a rare inherited form of the disease usually detected soon after birth. It affects children mainly and may result in premature loss of teeth and peremptory gum infections. The most severe form of chronic congenital neutropenia is known as Kostmann’s syndrome. It is genetically heterogeneous. Most commonly, it arises as a result of new,autosomal dominant mutations in the gene, ELA2, encoding the neutrophil granule protease, neutrophil elastase, NE. The gene responsible for many cases of autosomal recessively inherited severe congenital neutropenia is HAX1. The mechanism for congenital neutropenia is not well-understood. There is evidence that mutations in neutrophil elastase, or in other genes associated with syndromic forms of neutropenia, disrupt its intracellular trafficking. Apoptosis may be a final effector for neutropenia, but the original studies from Dale and Aprikian supporting this pathway were retracted.
Cyclic neutropenia — tends to occur every three weeks and lasting three to six days at a time due to changing rates of cell production by the bone marrow. It is often present among several members of the same family. Cyclic neutropenia is also the result of autosomal dominantly inherited mutations in ELA2, the gene encoding neutrophil elastase.
Idiopathic neutropenia — a rare form of neutropenia which develops in children and adults usually in response to an illness. It is diagnosed when the disorder cannot be attributed to any other diseases and often causes life-threatening infections.
Myelokathexis — a rare form of inherited autosomal dominant disease associated with severe neutropenia. Some but not all patients have Warts, Hypogammaglobulinemia, and recurrent Infections. Therefore myelokathexis is also known as the W.H.I.M. syndrome. In spite of severe neutropenia (low number of neutrophils) in peripheral blood of myelokathexis patients, their bone marrow is hypercellular and it is packed with mature neutrophils indicating an impaired mobilization of hematopoietic cells in this disorder. Truncating mutations in the human cytokine receptor CXCR4 gene were identified in most of the families afflicted by myelokathexis. The molecular mechanism is not yet defined. Recent reports demonstrate that CXCR4 mutations appear to result in an increased sensitivity of bone marrow hematopoietic cells to its ligand, a stromal-derived growth factor SDF-1 that provides proliferative and survival signals.
Autoimmune neutropenia — most common in infants and young children where the body identifies the neutrophils as enemies and makesantibody to destroy them. This form usually lessens in severity within two years of diagnosis.
Drug-induced neutropenia — Many drugs can cause agranulocytosis (complete absence of white cells) and neutropenia. Manyanti-neoplastic drugs cause agranulocytosis and neutropenia by bone marrow suppression. Neutropenia and agranulocytosis can also result from antibody or complement-mediated damage to the stem cells. Some drugs may cause increased peripheral destruction of white cells. About 75% of all cases of agranulocytosis in the United States are related to medication. Clozapine,procainamide, anti-thyroid drugs (e.g. methimazole, and sulfasalazine are at the top of the list of drugs causing this problem, but many others (such as antiepileptics) have been implicated.
References
- ↑ Hsieh MM, Everhart JE, Byrd-Holt DD, Tisdale JF, Rodgers GP (2007). "Prevalence of neutropenia in the U.S. population: age, sex, smoking status, and ethnic differences". Ann. Intern. Med. 146 (7): 486–92. PMID 17404350.