Leukocytosis Definition: Leukocytosis is a medical term used to describe an increase in the number of white blood cells (WBCs) in the blood. Typically, a WBC count above 11,000 cells per microliter is considered leukocytosis, though this threshold can vary slightly depending on the laboratory reference values. White blood cells, also known as leukocytes, play a crucial role in the immune system, helping the body to fight infections and other diseases. Types of Leukocytosis: Leukocytosis can be classified based on which type of white blood cell is elevated: 1. Neutrophilia: Increase in neutrophils, often in response to bacterial infections, inflammation, or stress. 2. Lymphocytosis: Increase in lymphocytes, commonly associated with viral infections, chronic infections, and some cancers. 3. Monocytosis: Increase in monocytes, seen in chronic infections (like tuberculosis) and inflammatory diseases. 4. Eosinophilia: Increase in eosinophils, typically related to allergic reactions, parasitic infections, or autoimmune diseases. 5. Basophilia: Increase in basophils, less common, and associated with chronic myeloproliferative disorders and certain allergic reactions. Causes of Leukocytosis: Leukocytosis can result from various physiological and pathological conditions:  Infections: Bacterial, viral, fungal, or parasitic infections can stimulate the bone marrow to produce more WBCs.  Inflammation: Conditions such as rheumatoid arthritis or inflammatory bowel disease can cause an increase in WBCs.  Stress: Physical or emotional stress can lead to a transient rise in WBC count.  Medications: Certain medications like corticosteroids and beta-agonists can induce leukocytosis.  Leukemia and other cancers: Hematologic malignancies can cause abnormally high WBC counts.  Smoking: Chronic smoking is associated with elevated WBC levels.  Other: Conditions like tissue damage (from burns or trauma), splenectomy, and immune responses can also contribute to leukocytosis. Clinical Presentation: Leukocytosis itself may not produce symptoms and is often found incidentally during routine blood tests. When symptomatic, the presentation is usually related to the underlying cause. For instance, patients with an infection may experience fever, fatigue, or localized symptoms depending on the infection site. Diagnosis: The diagnosis of leukocytosis is based on a complete blood count (CBC) that shows elevated WBC levels. Further evaluation involves a differential count to identify which type of WBC is elevated. Additional tests, including blood cultures, imaging, and bone marrow biopsy, may be needed to identify the underlying cause. Management: Treatment of leukocytosis focuses on addressing the underlying cause. For example, if an infection is the cause, antibiotics or antivirals may be used. If medication-induced, altering the drug regimen may be necessary. In cases of leukemia or other hematologic disorders, more specific treatments like chemotherapy may be required. Prognosis: The prognosis of leukocytosis depends on the underlying cause. When related to benign or transient conditions, the outlook is usually good. However, when associated with malignancies or severe infections, the prognosis may be more guarded. Regular monitoring and treatment of the underlying condition are essential for managing leukocytosis effectively.