What is the cause of leukopenia (low white blood cell count)?

From the Guidelines

Leukopenia should not be treated with hematopoietic growth factors such as granulocyte colony-stimulating factor (G-CSF) unless the patient has febrile neutropenia or is at high risk of infection, as the use of these factors does not significantly reduce morbidity, mortality, or improve quality of life in most cases 1.

Causes and Treatment

Leukopenia is a condition characterized by an abnormally low white blood cell count, typically below 4,000 cells per microliter of blood. This condition requires medical evaluation as it can significantly impair the body's ability to fight infections. Treatment depends on the underlying cause, which may include:

• Viral infections
• Certain medications, such as azathioprine (AZA) and 6-mercaptopurine, which can cause leukopenia in up to 3.2% of patients 1
• Autoimmune disorders
• Bone marrow problems If medication-induced, discontinuing the offending drug under medical supervision may resolve the condition. For mild cases, monitoring and preventive measures against infection may be sufficient.

Management

More severe cases might require medications like granulocyte colony-stimulating factors (G-CSF) such as filgrastim (Neupogen) at doses of 5-10 mcg/kg/day subcutaneously until white blood cell counts normalize. However, the use of G-CSF should be reserved for patients with febrile neutropenia or those at high risk of infection, as the incidence of febrile neutropenia (FNP) and mortality rates are relatively low for most standard chemotherapies 1. Patients with leukopenia should practice good hygiene, avoid crowds and sick individuals, maintain proper nutrition with adequate protein and vitamins, and seek immediate medical attention for signs of infection such as fever, as infections can progress rapidly due to the compromised immune system.

Key Considerations

• The decision to use hematopoietic growth factors should be based on the individual patient's risk of infection and febrile neutropenia, rather than the presence of leukopenia alone 1.
• Azathioprine and 6-mercaptopurine can cause leukopenia, and the incidence of this side effect can be influenced by factors such as thiopurine methyltransferase (TPMT) genotype and enzyme activity, as well as drug interactions and blood transfusion 1.
• Patients with leukopenia should be closely monitored for signs of infection and receive prompt treatment if necessary to prevent complications and improve quality of life.

From the FDA Drug Label

Decreased platelet count (thrombocytopenia). Your healthcare provider will check your blood during treatment with NEUPOGEN Tell your healthcare provider if you have unusual bleeding or bruising during treatment with NEUPOGEN. This could be a sign of decreased platelet counts, which may reduce the ability of your blood to clot. Increased white blood cell count (leukocytosis). Your healthcare provider will check your blood during treatment with NEUPOGEN.

The drug label does mention leukocytosis, which is an increase in white blood cell count, but it does not directly address leukopenia, which is a decrease in white blood cell count. Therefore, the information provided does not directly support an answer to the question about leukopenia. The FDA drug label does not answer the question.

From the Research

Definition and Causes of Leukopenia

• Leukopenia is an abnormal reduction of circulating white blood cells, especially the granulocytes 2.
• The term leukopenia is often used interchangeably with neutropenia 2.
• Leukopenia can result from reduced production of white blood cells or increased utilization and destruction, or both 2.
• Infection, drugs, malignancy, megaloblastosis, hypersplenism, and immunoneutropenia are responsible for most cases of neutropenia 2.

Diagnosis and Assessment of Leukopenia

• To get close to the diagnosis, it's always useful to check previous blood counts of the patient to get a feeling for the dynamic development of the leukopenia 3.
• A manual counted peripheral blood smear is an essential step towards the right diagnosis in leukopenia 3.
• Assessment of patients with neutropenia should be guided by the severity on presentation, the duration of leukopenia, and the clinical status of the patient 4.

Management and Treatment of Leukopenia

• Management requires identification of the cause and effective antimicrobial therapy, especially when serious systemic infection is present 2.
• Patients with febrile neutropenia should undergo treatment with antibiotics 4.
• The use of CSF-primed PBPC can significantly improve hematopoietic recovery after high-dose chemotherapy and autologous BM support 5.
• G-CSF was initially used to promote the production of neutrophils in patients with chemotherapy-induced neutropenia and helped to revolutionize the delivery of cancer therapy 6.

Complications and Risks of Leukopenia

• The major danger of neutropenia is the risk of infection 2.
• Leukopenia can be life-threatening for the patient, especially if the patient presents with an agranulocytosis and fever 3.
• Patients with neutropenia can develop life-threatening bacterial infections 4.
• The risk of febrile neutropenia should be assessed systematically in neutropenic patients 4.