From the Guidelines
Low neutrophil count, or neutropenia, is primarily caused by bone marrow suppression, autoimmune disorders, certain medications, and infections, with the most critical factor being the duration and depth of neutropenia, as evidenced by the increased risk of infection and mortality in patients with profound, prolonged neutropenia 1.
Causes of Neutropenia
The causes of low neutrophil count can be categorized into several groups, including:
- Bone marrow suppression, which can result from chemotherapy, radiation therapy, or bone marrow disorders like leukemia and myelodysplastic syndromes
- Autoimmune conditions, such as lupus and rheumatoid arthritis, which may trigger the immune system to attack neutrophils
- Certain medications, including antibiotics (trimethoprim-sulfamethoxazole, penicillin), antipsychotics (clozapine), and antithyroid drugs (methimazole), which can suppress neutrophil production
- Infections, such as viral infections (HIV, hepatitis, influenza) and severe bacterial infections, which can temporarily decrease neutrophil counts or consume neutrophils faster than they can be produced
- Nutritional deficiencies, particularly vitamin B12 and folate, which can impair neutrophil development
- Genetic disorders, such as congenital neutropenia and cyclic neutropenia, which cause inherited neutrophil production problems
- Splenic sequestration, where an enlarged spleen traps and destroys neutrophils, can also contribute to low counts
Treatment and Management
Treatment depends on identifying and addressing the underlying cause, which may include stopping offending medications, treating infections, or using medications like filgrastim (G-CSF) to stimulate neutrophil production in severe cases, as supported by the use of G-CSF in patients with severe chronic neutropenia 1.
Key Considerations
It is essential to note that the risk of infection increases with the depth and duration of neutropenia, and prevention and appropriate management of febrile neutropenia (FN) is crucial to reduce the rate of major complications and mortality, which can be as high as 11% in the context of FN 1.
From the Research
Causes of Low Neutrophil Count
- Neutropenia, a deficiency of neutrophils, can be caused by various factors, including congenital marrow defects, intrinsic and acquired disorders 2
- Chemotherapy-induced neutropenia is a common cause of low neutrophil count, particularly in cancer patients 3, 4
- Autoimmune neutropenia (AIN) is another cause of low neutrophil count, where the body's immune system attacks and destroys its own neutrophils 5
- Severe chronic neutropenia can be caused by a combination of factors, including genetic disorders, bone marrow failure, and certain medications 6, 2
Risk Factors
- Patients undergoing myelosuppressive chemotherapy are at high risk of developing neutropenia 6, 3, 4
- Individuals with a history of oral ulcers and inflammation, and recurrent skin infections are more likely to have severe neutropenia 2
- Adults with autoimmune neutropenia are at risk of recurring infections, particularly respiratory tract infections 5
Diagnostic Evaluation
- Evaluation of patients with neutropenia begins with confirmation of neutropenia and examination of a blood smear 2
- A careful review of the patient's medical history, family history, and physical examination is extremely important 2
- Examination of a bone marrow aspirate and/or biopsy and cytogenetic testing are primary for diagnostic evaluation 2