Neutropenia refers to a reduction in number of neutrophils circulating in the blood. As with deficiencies in other types of blood cell, neutropenia may occur due to failure to produce sufficient cells or due to excessive loss of cells as part of a pathological process. The major causes of neutropenia are:
- Infections caused by Gram negative bacteria which are able to produce endotoxin.
- Diseases that result in reduced production of cell in the bone marrow. In these diseases, neutropenia may be accompanied by other '-penias' and this may result in deficiencies of all of the blood cell lines: pancytopenia. Examples of this type of disease include:
- Radiotherapy and cytotoxic chemotherapy
- Toxins including bracken, chloramphenicol, trimethoprim-potentiated sulphonamides in Dobermann dogs and oestrogens.
- Infection with viruses that have a tropism for rapidly dividing cells, including canine parvovirus, canine distemper and infectious canine hepatitis. Feline panleucopaenia may result in multiple '-cytopenias'.
- Myelophthisis that may be due to myelofibrosis or to the growth of tumours that replace or displace normal bone marrow. The most common type of tumour that cause myelophthisis are myeloproliferative or lymphoproliferative diseases.