LEUKOCYTOSIS

47 LEUKOCYTOSIS



General Discussion


Leukocytosis is defined as a white blood cell (WBC) count greater than 11 000 per mm3. Circulating leukocytes consist of neutrophils, monocytes, eosinophils, basophils, and lymphocytes. Any one or all of these cell types may increase to abnormal levels in peripheral blood in response to various stimuli. An increase in neutrophils is the most common cause of leukocytosis. In most instances, elevated WBC counts are the result of normal bone marrow reacting to infection or inflammation. Leukocytosis may also occur as a result of physical or emotional stress. Causes of stress leukocytosis include anxiety, overexertion, seizures, anesthesia, and epinephrine administration. Stress leukocytosis reverses within hours of elimination of the causative factor. Leukocytosis may also be caused by medications, malignancy, hemolytic anemia, and splenectomy.


A WBC response of more than 50 000 per mm3 associated with a cause outside the bone marrow is termed a leukemoid reaction, which is usually caused by a relatively benign process such as infection or inflammation.


Certain clinical factors increase the suspicion that a leukocytosis may be caused by an underlying bone marrow disorder. These factors include a WBC count greater than 30 000 per mm3, concurrent anemia or thrombocytopenia, life-threatening infection or immunosuppression, lethargy, or significant weight loss. Other concerning factors include bleeding, bruising, or petechiae. Evidence of enlargement of the liver, spleen, or lymph nodes also suggests an underlying bone marrow disorder. The first step in evaluating a leukocytosis is to examine the WBC differential to determine which WBC type is elevated.


Neutrophilia usually reflects the inflammatory response to acute or subacute infections, so it should trigger a diagnostic search for its cause. When neutrophilia occurs in the absence of evidence of acute inflammation or illness, other explanations should be considered. These include chemical effects from medications, malignancies, and chronic myeloproliferative disorders. A peripheral blood smear that shows circulating blasts suggests an acute leukemia and leukoerythroblastic blasts suggests myelofibrosis or another marrow-infiltrating process. In the case of a simple left-shifted neutrophilia, chronic myelogenous leukemia (CML) or another myeloproliferative disorder must be distinguished from a leukemoid reaction. Diagnostic tests are available to help make this distinction and are outlined below.


Monocytosis is defined as absolute peripheral blood monocyte counts greater than 0.50 × 109/L. Monocytosis is often seen in patients with tuberculosis, syphilis, sarcoidosis, fungal infections, and ulcerative colitis. Mild monocytosis is common with Hodgkin’s disease and a variety of cancers. Significant monocytosis is most often seen with hematopoietic malignancies. Monocytosis that persists should be considered a marker of a myeloproliferative disorder until proved otherwise by bone marrow biopsy and cytogenetic studies.


Eosinophilia occurs when the eosinophil count in the peripheral blood exceeds 0.4 × 109/L. The first diagnostic step is to exclude the possibility that eosinophilia is caused by drugs, parasite infection, asthma, allergic conditions, vasculitides, lymphoma, or metastatic cancer.


Peripheral blood basophilia is very rare and suggests chronic basophilic leukemia. Bone marrow biopsy and hematology consultation are recommended.


Lymphocytosis is defined as a lymphocyte count greater than 5.0 × 109/L. Mild to moderate lymphocytosis (lymphocyte counts less than 12 × 109/L) is most commonly caused by viral infection. With the exception of pertussis, acute bacterial infections rarely cause lymphocytosis. Most patients with lymphocytosis have signs of an underlying illness. In patients who do not have evidence of an infectious process or benign disorder, the diagnostic approach depends on establishing a tissue diagnosis to exclude malignant disease.



Causes of Neutrophilia



Chemicals
• Ethylene glycol

• Histamine

• Mercury poisoning

• Venoms (reptiles, insects, jellyfish)

Drugs
• Corticosteroids

• Epinephrine

• Lithium

• Granulocyte colony stimulating factor

• Granulocyte–macrophage colony stimulating factor

Endocrine and metabolic disorders
• Ketoacidosis

• Lactic acidosis

• Thyrotoxicosis

Infections
• Bacteria

• Fungi

• Parasites

• Rickettsia

• Viruses

Myeloproliferative disorders
• Acute leukemia

• Agnogenic myeloid metaplasia

• Chronic myelogenous leukemia

• Essential thrombocytosis

• Polycythemia vera

Neoplastic disorders
• Breast carcinoma

• Bronchogenic carcinoma

• Gastric carcinoma

• Lymphoma, especially Hodgkin’s disease

• Melanoma

• Metastatic cancer to bone marrow

• Pancreatic carcinoma

• Renal cell carcinoma

Non-neoplastic hematologic disorders
• Acute hemolytic anemias

• Acute transfusion reactions

• Postsplenectomy

• Recovery from marrow failure

Other disorders
• Eclampsia

• Exfoliative dermatitis

• Hypoxia

• Pregnancy

• Tissue necrosis

Rheumatologic and autoimmune disorders
• Autoimmune hemolytic anemia

Related posts:

  1. ARTHRITIS AND ARTHRALGIA
  2. HAIR LOSS
  3. HYPOTHYROIDISM
  4. SYNCOPE

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Aug 17, 2016 | Posted by in PEDIATRICS | Comments Off on LEUKOCYTOSIS

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