Updated: Nov 3, 2009
Leukocytosis refers to an increase in the total number of WBCs due to any cause. From a practical standpoint, leukocytosis is traditionally classified according to the component of white cells that contribute to an increase in the total number of WBCs. Therefore, leukocytosis may be caused by an increase in (1) neutrophil count (ie, neutrophilia), (2) lymphocyte count (ie, lymphocytosis), (3) monocyte count (ie, monocytosis), (4) eosinophilic granulocyte count (ie, eosinophilia), (5) basophilic granulocyte count (ie, basophilia), or (6) immature cells (eg, blasts). A combination of any of the above may be involved.
Neutrophilia also is divided into 4 categories based on the mechanism of neutrophilia: (1) increased production, (2) decreased egress from vascular space (demargination), (3) increased mobilization from the marrow storage pool, and (4) reduced margination into the tissue.
Clinically, dividing leukocytosis on the basis of its causes is more convenient. By dividing it according to causes, leukocytosis can be immediately applied for diagnostic purposes. Leukocytosis can be caused by infection, inflammation, allergic reaction, malignancy, hereditary disorders, or other miscellaneous causes.
Leukocytosis can be a reaction to various infectious, inflammatory, and, in certain instances, physiologic processes (eg, stress, exercise). This reaction is mediated by several molecules, which are released or upregulated in response to stimulatory events that include growth or survival factors (eg, granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, c-kit ligand), adhesion molecules (eg, CD11b/CD18), and various cytokines (eg, interleukin-1, interleukin-3, interleukin-6, interleukin-8, tumor necrosis factor).
The peripheral leukocyte count is determined by several mechanisms, including (1) the size of precursor and storage pool of myeloid and lymphoid cells, (2) the rate of release of the cells from the storage pool in the bone marrow, (3) the rate of marginating cells out of blood vessels into the tissues, and (4) the rate of consumption of the cells in the tissues (ie, cell loss). The growth factors, adhesion molecules, and cytokines control all 4 mechanisms listed above. For a detailed discussion, see Robbins Pathologic Basis of Disease.1
Hyperleukocytosis (WBC count >100 X 109/L, or >100 X 103/µL) occurs in leukemia and myeloproliferative disorders. This is certainly due to its inherent autonomous growth potential of malignant cells. Hyperleukocytosis often causes vascular occlusion, resulting in ischemia, hemorrhage, and edema of the involved organs. The problem is most commonly observed in acute myelogenous leukemia with high WBC counts. Individuals often clinically present with mental status changes, stroke, and renal or pulmonary insufficiency. If the neutrophil count exceeds 30,000/μ L as a reaction to extrinsic factors, such as infection, it is sometimes called a leukemoid reaction.
In a person with sickle cell disease, the baseline WBC count is elevated with a mean of 12-15 X 109/L (12-15 X 103/µL). This change mainly is due to a shift of granulocytes from the marginated pool to the circulating compartment. The segmented neutrophil count increases in both vaso-occlusive crisis and in bacterial infection in patients with sickle cell disease.
Clinically significant morbidity and mortality are frequently observed in patients with leukemic hyperleukocytosis. Hyperleukocytosis may result in tumor lysis syndrome and disseminated intravascular coagulopathy. In addition to well-known complications (eg, acute respiratory failure, pulmonary hemorrhage, CNS infarction, hemorrhage), splenic infarction, myocardial ischemia, renal failure due to renal vessel leukostasis, and priapism have been reported.
Always remember age-specific reference ranges for total WBC, neutrophil, and lymphocyte counts. The total WBC and neutrophil count in neonates younger than 1 week are physiologically higher than those of older children and adults. The proportion of lymphocytes and absolute lymphocyte count in children younger than 6 years are higher than those in adults. Failure to recognize age-specific lymphocytosis may lead to unnecessary investigations (see the table below for reference ranges of age-related leukocyte counts).
Infants (usually aged <3 mo) have small storage pools of neutrophils. In severe infections, their neutrophilic demands often exceeded their supplies. Therefore, young infants may have neutropenia in response to serious infection.
Normal Leukocyte Counts
| Total Leukocytes* | Lymphocytes | Neutrophils† | Monocytes | Eosinophils | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Age | Mean | Range | Mean | Range | % | Mean | Range | % | Mean | % | Mean | % | |||||
| Birth | ... | ... | 4.2 | 2-7.3 | ... | 4 | 2-6 | ... | 0.6 | ... | 0.1 | ... | |||||
| 12 h | ... | ... | 4.2 | 2-7.3 | ... | 11 | 7.8-14.5 | ... | 0.6 | ... | 0.1 | ... | |||||
| 24 h | ... | ... | 4.2 | 2-7.3 | ... | 9 | 7-12 | ... | 0.6 | ... | 0.1 | ... | |||||
| 1-4 wk | ... | ... | 5.6 | 2.9-9.1 | ... | 3.6 | 1.8-5.4 | ... | 0.7 | ... | 0.2 | ... | |||||
| 6 mo | 11.9 | 6-17.5 | 7.3 | 4-13.5 | 61 | 3.8 | 1-8.5 | 32 | 0.6 | 5 | 0.3 | 3 | |||||
| 1 y | 11.4 | 6-17.5 | 7.0 | 4-10.5 | 61 | 3.5 | 1.5-8.5 | 31 | 0.6 | 5 | 0.3 | 3 | |||||
| 2 y | 10.6 | 6-17 | 6.3 | 3-9.5 | 59 | 3.5 | 1.5-8.5 | 33 | 0.5 | 5 | 0.3 | 3 | |||||
| 4 y | 9.1 | 5.5-15.5 | 4.5 | 2-8 | 50 | 3.8 | 1.5-8.5 | 42 | 0.5 | 5 | 0.3 | 3 | |||||
| 6 y | 8.5 | 5-14.5 | 3.5 | 1.5-7 | 42 | 4.3 | 1.5-8 | 51 | 0.4 | 5 | 0.2 | 3 | |||||
| 8 y | 8.3 | 4.5-13.5 | 3.3 | 1.5-6.8 | 39 | 4.4 | 1.5-8 | 53 | 0.4 | 4 | 0.2 | 2 | |||||
| 10 y | 8.1 | 4.5-13.5 | 3.1 | 1.5-6.5 | 38 | 4.4 | 1.8-8 | 54 | 0.4 | 4 | 0.2 | 2 | |||||
| 16 y | 7.8 | 4.5-13 | 2.8 | 1.2-5.2 | 35 | 4.4 | 1.8-8 | 57 | 0.4 | 5 | 0.2 | 3 | |||||
| 21 y | 7.4 | 4.5-11 | 2.5 | 1-4.8 | 34 | 4.4 | 1.8-7.7 | 59 | 0.3 | 4 | 0.2 | 3 | |||||
* Numbers of leukocytes are in X 109 \L or thousands per μ L; ranges are estimates of 95% confidence limits; and percentages refer to differential counts.
† Neutrophils include band cells at all ages and a small number of metamyelocytes and myelocytes in the first few days of life.
| Acute Lymphoblastic Leukemia | Hypereosinophilic Syndrome |
| Acute Myelocytic Leukemia | Leukocyte Adhesion Deficiency |
| Appendicitis | Pertussis |
| Asplenia | Polycythemia |
| Bacteremia | Polycythemia Vera |
| Down Syndrome | Sickle Cell Anemia |
Chronic granulocytic (myelogenous) leukemia
In most cases, treatment for leukocytosis is not necessary.
Hyperleukocytosis in leukemia is often complicated by a tumor lysis syndrome, which includes a high serum uric acid and uric acid nephropathy. Prompt measures to reduce serum uric acid and prevent uric acid nephropathy are required.
These drugs are used to prevent acute uric acid nephropathy associated with leukocytosis in myeloproliferative disease and leukemia.
Inhibits xanthine oxidase, the enzyme that synthesizes uric acid from hypoxanthine. Reduces synthesis of uric acid without disrupting biosynthesis of vital purines. Reduces plasma concentration and urine excretion of uric acid; simultaneously increases plasma concentration and urine excretion of more soluble oxypurine precursors.
200-300 mg/d PO divided bid/qid; alternatively,
200-400 mg/m2/d IV qd or divided q6-12h; not to exceed 600 mg/m2/d
10 mg/kg/d (or 200-300 mg/m2/d) PO divided bid/qid; alternatively, 200 mg/m2/d IV qd or divided q6-12h
Alcohol decreases effects; increased incidence of rash with concurrent ampicillin and amoxicillin; large amounts of vitamin C acidify urine and may cause kidney stones; inhibits metabolism of azathioprine and mercaptopurine
Documented hypersensitivity
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Caution in renal insufficiency (decrease dose), hepatic disease, or dehydration; may cause Stevens-Johnson syndrome; discontinue at first sign of rash
Recombinant form of urate oxidase (derived from Saccharomyces cerevisiae -synthesized Aspergillus flavus), which oxidizes uric acid to allantoin (soluble and inactive). Indicated for treatment and prophylaxis of severe hyperuricemia associated with treatment of malignancy. Hyperuricemia causes precipitant in kidneys, leading to acute renal failure. Unlike uric acid, allantoin soluble and easily excreted by kidneys. Elimination half-life is 18 h.
0.15-0.2 mg/kg/d IV infused over 30 min for up to 5 d; dilute in 50 mL 0.9% NaCl
Administer as in adults
None reported
Documented hypersensitivity; glucose-6-phosphate dehydrogenase (G-6-PD) deficiency (possible severe acute hemolysis on exposure)
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
May cause hemolytic anemia secondary to hydrogen peroxide produced during uric acid oxidation; may cause methemoglobinemia; other adverse effects include fever, nausea, or vomiting; children <2 y may have increased vomiting, diarrhea, fever, and rash; avoid shaking or vortexing during reconstitution; highly antigenic, multiple administration may produce allergic reaction, anaphylaxis, or death; produces falsely low uric acid levels (accurate levels obtained by collecting blood into prechilled, heparin-containing tubes kept and centrifuged at 4°C); maintain resultant plasma at 4°C and analyze within 4 h of collection
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leukocytosis, white blood cell count, WBC count, increased WBCs, neutrophil count, neutrophilia, lymphocyte count, lymphocytosis, monocyte count, monocytosis, eosinophilic granulocyte count, eosinophilia, fever, abdominal pain
Susumu Inoue, MD, Professor of Pediatrics and Human Development, Michigan State University College of Human Medicine; Clinical Professor of Pediatrics, Wayne State University School of Medicine; Director of Pediatric Hematology/Oncology, Associate Director of Pediatric Education, Department of Pediatrics, Hurley Medical Center
Susumu Inoue, MD is a member of the following medical societies: American Academy of Pediatrics, American Society of Hematology, American Society of Pediatric Hematology/Oncology, International Society for Experimental Hematology, and Society for Pediatric Research
Disclosure: Nothing to disclose.
Gary R Jones, MD, Associate Medical Director, Clinical Development, Berlex Laboratories
Gary R Jones, MD is a member of the following medical societies: American Academy of Pediatrics, American Society of Pediatric Hematology/Oncology, and Western Society for Pediatric Research
Disclosure: Nothing to disclose.
Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine
Disclosure: Pfizer Inc Stock Investment from financial planner; Avanir Pharma Stock Investment from financial planner ; WebMD Salary and stock Employment and investment from financial planner
Gary D Crouch, MD, Program Director of Pediatric Hematology-Oncology Fellowship, Department of Pediatrics, Associate Professor, Uniformed Services University of the Health Sciences
Gary D Crouch, MD is a member of the following medical societies: American Academy of Pediatrics and American Society of Hematology
Disclosure: Nothing to disclose.
Helen SL Chan, MBBS, FRCP(C), FAAP, Senior Scientist, Research Institute; Professor, Division of Hematology/Oncology, Department of Pediatrics, The Hospital for Sick Children, University of Toronto, Canada
Helen SL Chan, MBBS, FRCP(C), FAAP is a member of the following medical societies: American Academy of Pediatrics, American Association for Cancer Research, American Society of Hematology, and Royal College of Physicians and Surgeons of Canada
Disclosure: Nothing to disclose.
Robert J Arceci, MD, PhD, King Fahd Professor of Pediatric Oncology, Professor of Pediatrics, Oncology and the Cellular and Molecular Medicine Graduate Program, Kimmel Comprehensive Cancer Center at Johns Hopkins University School of Medicine
Robert J Arceci, MD, PhD is a member of the following medical societies: American Association for Cancer Research, American Association for the Advancement of Science, American Pediatric Society, American Society of Hematology, and American Society of Pediatric Hematology/Oncology
Disclosure: Nothing to disclose.
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