Sandbox: Leukocytosis
Synonyms and keywords:  Elevated white blood cell count; Right-shift leukocytosis; Left-leukocytosis

# Overview
Leukocytosis  is an elevation of the white blood cell count above the normal range (greater than 11,000 per mm3). Leukocytosis is frequently a sign of an inflammatory response, most commonly the result of infection, but may also occur following certain parasitic infections, bone tumors, strenuous exercise, emotional stress, pregnancy,  anesthesia, and epinephrine administration. Leukocytosis may be classified into 5 subtypes: neutrophilia (most common), lymphocytosis, monocytosis, eosinophilia, and basophilia. Other classification, include: Left shift or right shift leucocytosis. The pathogenesis of leukocytosis is characterized by the increase of leukocytes (primarily neutrophils), followed by the proliferation and release of granulocyte and monocyte precursors in the bone marrow which is stimulated by several products of inflammation including C3a and G-CSF.

# Historical Perspective
- Leukocytosis was first discovered by Paul Kautchakoff, in 1846.

# Classification
- Leukocytosis may be classified into 5 subtypes:
- Neutrophilia (most common)
- Lymphocytosis
- Monocytosis
- Eosinophilia
- Basophilia.
- Leukocytosis may also be classified into 2 groups:
- Left shift (most common)
- Immature leukocytes increase
- Proliferation and release of granulocyte and monocyte precursors in the bone marrow
- Usually stimulated by several products of inflammation including C3a and G-CSF
- Right shift
- Reduced count or lack of "young neutrophils"
- Associated with the presence of "giant neutrophils
- Other variant of leukocytosis is the leukemoid reaction.
- The image below demonstrates a graphic figure that illustrates hematopoietic growth factors in leukocytosis.
- Hematopoietic growth factors in leukocytosis Courtesy of Wikipedia

# Pathophysiology
- The pathogenesis of leukocytosis is characterized by:
- An increased release of leukocytes from bone marrow storage pools
- Decreased margination of leukocytes onto vessel walls
- Decreased extravasation of leukocytes from the vessels into tissues
- Increase in number of precursor cells in the marrow

# Causes
- To see a comprehensive list of all causes of leukocytosis, please click here

# Epidemiology and Demographics
- Leukocytosis is very common.

## Age
- Patients of all age groups may develop leukocytosis.
- Normal white blood count differential changes with age.
- Leukocytosis in neonates is more common, compared to children and adults.

## Gender
- Leukocytosis affects men and women equally.

## Race
- There is no racial predilection for leukocytosis.

# Risk Factors
- Common risk factors in the development of leukocytosis, include:
- Physiologic processes (eg, stress, exercise, pregnancy)
- Drugs (e.g.corticosteroids, lithium, beta agonists)
- Trauma
- Stress

# Natural History, Complications and Prognosis
- The majority of patients with leukocytosis are initially symptomatic.
- Early clinical features, include:
- Fever
- Hyperhidrosis
- Fatigue
- Common complications of leukocytosis, include:
- Tumor lysis syndrome
- Disseminated intravascular coagulopathy
- Acute respiratory failure
- Pulmonary hemorrhage
- CNS infarction
- Splenic infarction
- Myocardial ischemia
- Renal failure
- Prognosis is generally depends on the underlying etiologies.

# Diagnosis

## Symptoms
- Leukocytosis is usually symptomatic.
- Symptoms of leukocytosis are often unspecific, such as:
- Weight loss
- Fevers of unknown origin
- Hyperhidrosis
- Chronic pain
- Fatigue
- Dyspnea
- Malaise
- Obtain history of the following:
- Clinical features
- Duration (e.g. days, weeks, months)
- Remainder of complete blood count

## Laboratory Findings
- Laboratory findings consistent with the diagnosis of leukocytosis, include:
- White blood cell count above the normal range
- Greater than 11,000 per mm3

# Treatment

## Medical Therapy
- The treatment for leukocytosis will depend on the underlying condition.