From the Guidelines
Leukocytosis can be caused by several factors besides infection, including stress, certain medications, inflammatory conditions, allergic reactions, certain cancers, bone marrow disorders, and other non-infectious conditions. The main non-infectious causes of leukocytosis include:
- Stress or intense physical exertion
- Certain medications (e.g., corticosteroids, lithium, beta-agonists)
- Inflammatory conditions (e.g., rheumatoid arthritis, inflammatory bowel disease) 1
- Allergic reactions
- Certain cancers, especially leukemia and lymphoma 1
- Bone marrow disorders
- Smoking
- Pregnancy
- Severe blood loss or hemolysis
- Splenectomy These causes lead to increased white blood cell production or release from the bone marrow, or decreased removal of white blood cells from circulation. For example, stress triggers the release of cortisol, which can cause demargination of white blood cells adhered to blood vessel walls. Corticosteroids have a similar effect. In cancers like leukemia, there's uncontrolled proliferation of white blood cells 1. Understanding these causes is crucial for accurate diagnosis and appropriate treatment of leukocytosis. In particular, chronic myeloid leukemia (CML) is a type of cancer that can cause leukocytosis, and it is characterized by the uncontrolled proliferation of white blood cells in the bone marrow 1. The diagnosis of CML is based on the presence of certain clinical and laboratory criteria, including a high white blood cell count, splenomegaly, and the presence of the Philadelphia chromosome 1. It's also important to note that some immunodeficiency disorders, such as severe combined immunodeficiency (SCID), can also present with leukocytosis, although this is often accompanied by other symptoms such as recurrent infections and failure to thrive 1. Overall, a thorough evaluation of the patient's medical history, physical examination, and laboratory results is necessary to determine the underlying cause of leukocytosis and to guide appropriate treatment.
From the Research
Causes of Leukocytosis
- Infections, such as pneumonia, urinary tract infection, soft-tissue infection, and C. difficile infection 2
- Physiological stress, including seizures, anesthesia, overexertion, surgery, exercise, trauma, and emotional stress 3, 4, 5
- Medications, such as corticosteroids, lithium, beta agonists, and other drugs 3, 4, 2
- Chronic inflammatory conditions, such as obesity and smoking 4
- Primary bone marrow disorders, including acute leukemias, chronic leukemias, and myeloproliferative disorders 3, 6
- Asplenia 4
- Allergic reactions, which can lead to increased eosinophil or basophil counts 3
- Necrosis or inflammation 2
Non-Malignant Causes
- Stressors, such as surgery, exercise, trauma, and emotional stress, can cause an acute leukocytosis 4
- Certain medications, such as corticosteroids and beta agonists, can elevate white blood cell counts 3, 4
- Physiological conditions, such as pregnancy, can have age- and pregnancy-specific normal ranges for the white blood cell count 4
Malignant Causes
- Acute leukemias, which can present with severe symptoms and require urgent referral to a hematology subspecialist 3, 6
- Chronic leukemias, which can present with less severe symptoms and are often diagnosed incidentally due to abnormal blood cell counts 3, 6
- Myeloproliferative disorders, which can cause an increase in white blood cell counts 3