Basophilia as an isolated finding is uncommon. However it is a common feature of myeloproliferative disorders and particularly prominent in chronic myelogenous leukemia.

Conditions Associated with Increased Numbers of Blood Basophils

- Allergy or inflammation

1. Ulcerative colitis

2. Drug, food, inhalant hypersensitivity

3. Erythroderma, urticaria

4. Juvenile rheumatoid arthritis

- Endocrinopathy

1. Diabetes mellitus

2. Estrogen administration

3. Hypothyroidism (myxedema)

- Infection

1. Chicken pox

2. Influenza

3. Smallpox

4. Tuberculosis

- Iron deficiency

- Exposure to ionizing radiation

- Neoplasia

1. "Basophilic leukemia" (see text)

- Myeloproliferative neoplasms (especially chronic myelogenous leukemia; also polycythemia vera, primary myelofibrosis, essential thrombocythemia)

- Carcinoma

As noted above, a leukemoid reaction is typically a response to an underlying medical issue. Causes of leukemoid reactions include:

- Severe hemorrhage (retroperitoneal hemorrhage)

- Drugs

- Use of sulfa drugs

- Use of dapsone

- Use of glucocorticoids

- Use of G-CSF or related growth factors

- All-trans retinoic acid (ATRA)

- Ethylene glycol intoxication

- Infections

- Clostridium difficile

- Tuberculosis

- Pertussis

- Infectious mononucleosis (lymphocyte predominant)

- Visceral larva migrans (eosinophil predominant)

- Asplenia

- Diabetic ketoacidosis

- Organ necrosis

- Hepatic necrosis

- Ischemic colitis

- As a feature of trisomy 21 in infancy (incidence of ~10%)

- As a paraneoplastic phenomenon (rare)

The environmental exposures that contribute to emergence of ALL is contentious and a subject of ongoing debate.

High levels of radiation exposure from nuclear fallout is a known risk factor for developing leukemia. Evidence whether less radiation, as from x-ray imaging during pregnancy, increases risk of disease remains inconclusive. Studies that have identified an association between x-ray imaging during pregnancy and ALL found only a slightly increased risk. Exposure to strong electromagnetic radiation from power lines has also been associated with a slightly increased risk of ALL. This result is questioned as no causal mechanism linking electromagnetic radiation with cancer is known.

High birth weight (greater than 4000g or 8.8lbs) is also associated with a small increased risk. The mechanism connecting high birth weight to ALL is also not known.

Evidence suggests that secondary leukemia can develop in individuals treated with certain types of chemotherapy, such as epipodophyllotoxins and cyclophosphamide.

There have been few individual epidemiological studies of CMML, due to the difficulty in the disease classification. CMML has an estimated incidence of less than 1 per 100,000 persons per year.

The median age of diagnosis is 65–75. CMML has a propensity for males rather than females, at a ratio of 1.5–3:1.

Leukemia is rarely associated with pregnancy, affecting only about 1 in 10,000 pregnant women. The management of leukemia in a pregnant patient depends primarily on the type of leukemia. Acute leukemias normally require prompt, aggressive treatment, despite significant risks of pregnancy loss and birth defects, especially if chemotherapy is given during the developmentally sensitive first trimester.

Given the definition of basophilia, diagnosis is made from a complete blood count where there are more than 10 basophils per liter of blood.

Basophils are a type of white blood cells. Basophils are the least common of the granulocytes, representing about 0.5 to 1% of circulating white blood cells. However, they are the largest type of granulocyte. They are responsible for inflammatory reactions during immune response, as well as in the formation of acute and chronic allergic diseases, including anaphylaxis, asthma, atopic dermatitis and hay fever. They can perform phagocytosis (cell eating), produce histamine and serotonin that induce inflammation, and heparin that prevents blood clotting. It used to be thought that basophils that have migrated from blood into their resident tissues (connective tissue) are known as mast cells, but this is no longer thought to be the case.

Basophils were discovered in 1879 by German physician Paul Ehrlich, who one year earlier had found a cell type present in tissues that he termed "mastzellen" (now mast cells). Ehrlich received the 1908 Nobel Prize in Physiology or Medicine for his discoveries.

The name comes from the fact that these leukocytes are basophilic, i.e., they are susceptible to staining by basic dyes, as shown in the picture.

Leukocytosis is very common in acutely ill patients. It occurs in response to a wide variety of conditions, including viral, bacterial, fungal, or parasitic infection, cancer, hemorrhage, and exposure to certain medications or chemicals including steroids.

For lung diseases such as pneumonia and tuberculosis, WBC count is very important for the diagnosis of the disease, as leukocytosis is usually present.

The mechanism that causes leukocytosis can be of several forms: 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, or an increase in number of precursor cells in the marrow.

Certain medications, including corticosteroids, lithium and beta agonists, may cause leukocytosis.

Leukocytosis is white cells (the leukocyte count) above the normal range in the blood. It is frequently a sign of an inflammatory response, most commonly the result of infection, but may also occur following certain parasitic infections or bone tumors as well as leukemia. It may also occur after strenuous exercise, convulsions such as epilepsy, emotional stress, pregnancy and labor, anesthesia, and epinephrine administration.

There are five principle types of leukocytosis:

1. Neutrophilia (the most common form)

2. Lymphocytosis

3. Monocytosis

4. Eosinophilia

5. Basophilia

This increase in leukocyte (primarily neutrophils) is usually accompanied by a "left upper shift" in the ratio of immature to mature neutrophils and macrophages. The proportion of immature leukocytes decreases due to proliferation and inhibition of granulocyte and monocyte precursors in the bone marrow which is stimulated by several products of inflammation including C3a and G-CSF.

Although it may indicate illness, leukocytosis is considered a laboratory finding instead of a separate disease. This classification is similar to that of fever, which is also a test result instead of a disease.

"Right shift" in the ratio of immature to mature neutrophils is considered with reduced count or lack of "young neutrophils" (metamyelocytes, and band neutrophils) in blood smear, associated with the presence of "giant neutrophils". This fact shows suppression of bone marrow activity, as a hematological sign specific for pernicious anemia and radiation sickness.

A leukocyte count above 25 to 30 x 10/L is termed a "leukemoid reaction", which is the reaction of a healthy bone marrow to extreme stress, trauma, or infection. It is different from leukemia and from leukoerythroblastosis, in which either immature white blood cells (acute leukemia) or mature, yet non-functional, white blood cells (chronic leukemia) are present in peripheral blood.

A new method developed using data from the M.D. Anderson Cancer Center found that a haemoglobin level of 2.5 x 10/L, >0% immature myeloid cells, >10% bone marrow blasts causes a reduced overall survival. This data allows cases of CMML to be stratified into low, intermediate-1, intermediate-2 and high risk groups. These groups have median survival times of 24, 15, 8 and 5 months respectively.

The term leukemoid reaction describes an increased

white blood cell count, or leukocytosis, which is a physiological response to stress or infection (as opposed to a primary blood malignancy, such as leukemia). It often describes the presence of immature cells such as myeloblasts or red blood cells with nuclei in the peripheral blood.

It may be lymphoid or myeloid.

Basophils contain large cytoplasmic granules which obscure the cell nucleus under the microscope when stained. However, when unstained, the nucleus is visible and it usually has two . The mast cell, another granulocyte, is similar in appearance and function. Both cell types store histamine, a chemical that is secreted by the cells when stimulated. However, they arise from different branches of hematopoiesis, and mast cells usually do not circulate in the blood stream, but instead are located in connective tissue. Like all circulating granulocytes, basophils can be recruited out of the blood into a tissue when needed.