The term leukemoid reaction describes an increased

white blood cell White blood cells, also called leukocytes or leucocytes, are the cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. All white blood cells are produced and derived from mult ...

count (> 50,000 cells/μL), which is a physiological response to stress or infection (as opposed to a primary blood

malignancy Malignancy () is the tendency of a medical condition to become progressively worse. Malignancy is most familiar as a characterization of cancer. A ''malignant'' tumor contrasts with a non-cancerous ''benign'' tumor in that a malignancy is not s ...

, such as

leukemia Leukemia ( also spelled leukaemia and pronounced ) is a group of blood cancers that usually begin in the bone marrow and result in high numbers of abnormal blood cells. These blood cells are not fully developed and are called ''blasts'' or ...

). 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 The lymphatic system, or lymphoid system, is an organ system in vertebrates that is part of the immune system, and complementary to the circulatory system. It consists of a large network of lymphatic vessels, lymph nodes, lymphatic or lymphoid ...

or myeloid.

Causes

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

hemorrhage Bleeding, hemorrhage, haemorrhage or blood loss, is blood escaping from the circulatory system from damaged blood vessels. Bleeding can occur internally, or externally either through a natural opening such as the mouth, nose, ear, urethra, vag ...

(retroperitoneal hemorrhage) * Drugs ** Use of sulfa drugs ** Use of

dapsone Dapsone, also known as 4,4'-sulfonyldianiline (SDA) or diaminodiphenyl sulfone (DDS), is an antibiotic commonly used in combination with rifampicin and clofazimine for the treatment of leprosy. It is a second-line medication for the treatment ...

** Use of

glucocorticoid Glucocorticoids (or, less commonly, glucocorticosteroids) are a class of corticosteroids, which are a class of steroid hormones. Glucocorticoids are corticosteroids that bind to the glucocorticoid receptor that is present in almost every verte ...

s ** Use of

G-CSF Granulocyte colony-stimulating factor (G-CSF or GCSF), also known as colony-stimulating factor 3 (CSF 3), is a glycoprotein that stimulates the bone marrow to produce granulocytes and stem cells and release them into the bloodstream. Functional ...

or related growth factors ** All-trans retinoic acid (ATRA) * Ethylene glycol intoxication * Infections ** Clostridium difficile **

Tuberculosis Tuberculosis (TB) is an infectious disease usually caused by ''Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can also affect other parts of the body. Most infections show no symptoms, in w ...

Pertussis Whooping cough, also known as pertussis or the 100-day cough, is a highly contagious bacterial disease. Initial symptoms are usually similar to those of the common cold with a runny nose, fever, and mild cough, but these are followed by two o ...

Infectious mononucleosis Infectious mononucleosis (IM, mono), also known as glandular fever, is an infection usually caused by the Epstein–Barr virus (EBV). Most people are infected by the virus as children, when the disease produces few or no symptoms. In young adult ...

(

lymphocyte A lymphocyte is a type of white blood cell (leukocyte) in the immune system of most vertebrates. Lymphocytes include natural killer cells (which function in cell-mediated, cytotoxic innate immunity), T cells (for cell-mediated, cytotoxic ad ...

predominant) ** Visceral larva migrans (

eosinophil Eosinophils, sometimes called eosinophiles or, less commonly, acidophils, are a variety of white blood cells (WBCs) and one of the immune system components responsible for combating multicellular parasites and certain infections in vertebrates. ...

predominant) * Asplenia *

Diabetic ketoacidosis Diabetic ketoacidosis (DKA) is a potentially life-threatening complication of diabetes mellitus. Signs and symptoms may include vomiting, abdominal pain, deep gasping breathing, increased urination, weakness, confusion and occasionally los ...

* Organ necrosis ** Hepatic necrosis **

Ischemic colitis Ischemic colitis (also spelled ischaemic colitis) is a medical condition in which inflammation and injury of the large intestine result from inadequate blood supply. Although uncommon in the general population, ischemic colitis occurs with greater ...

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

paraneoplastic phenomenon A paraneoplastic syndrome is a syndrome (a set of signs and symptoms) that is the consequence of a tumor in the body (usually a cancerous one), specifically due to the production of chemical signaling molecules (such as hormones or cytokines) by ...

(rare)

Diagnosis

Conventionally, a leukocytosis exceeding 50,000 WBC/mm³ with a significant increase in early

neutrophil Neutrophils (also known as neutrocytes or heterophils) are the most abundant type of granulocytes and make up 40% to 70% of all white blood cells in humans. They form an essential part of the innate immune system, with their functions varying in ...

precursors is referred to as a leukemoid reaction. p. 803. The peripheral blood smear may show

myelocyte A myelocyte is a young cell of the granulocytic series, occurring normally in bone marrow (can be found in circulating blood when caused by certain diseases). Structure When stained with the usual dyes, the cytoplasm is distinctly basophili ...

metamyelocyte A metamyelocyte is a cell undergoing granulopoiesis, derived from a myelocyte, and leading to a band cell. It is characterized by the appearance of a bent nucleus, cytoplasmic granules, and the absence of visible nucleoli. (If the nucleus is no ...

promyelocyte A promyelocyte (or progranulocyte) is a granulocyte precursor, developing from the myeloblast and developing into the myelocyte. Promyelocytes measure 12-20 microns in diameter. The nucleus of a promyelocyte is approximately the same size as a ...

s, and rarely myeloblasts; however, there is a mixture of early mature neutrophil precursors, in contrast to the immature forms typically seen in

acute leukemia Acute leukemia or acute leukaemia is a family of serious medical conditions relating to an original diagnosis of leukemia. In most cases, these can be classified according to the lineage, myeloid or lymphoid, of the malignant cells that grow unco ...

. Serum leukocyte alkaline phosphatase is normal or elevated in leukemoid reaction, but is depressed in

chronic myelogenous leukemia Chronic myelogenous leukemia (CML), also known as chronic myeloid leukemia, is a cancer of the white blood cells. It is a form of leukemia characterized by the increased and unregulated growth of myeloid cells in the bone marrow and the accumula ...

. The

bone marrow Bone marrow is a semi-solid tissue found within the spongy (also known as cancellous) portions of bones. In birds and mammals, bone marrow is the primary site of new blood cell production (or haematopoiesis). It is composed of hematopoieti ...

in a leukemoid reaction, if examined, may be hypercellular but is otherwise typically unremarkable. Leukemoid reactions are generally

benign Malignancy () is the tendency of a medical condition to become progressively worse. Malignancy is most familiar as a characterization of cancer. A ''malignant'' tumor contrasts with a non-cancerous ''benign'' tumor in that a malignancy is not s ...

and are not dangerous in and of themselves, although they are often a response to a significant disease state (see ''Causes'' above). However, leukemoid reactions can resemble more serious conditions such as

(CML), which can present with identical findings on the peripheral blood smear. Historically, various clues including the leukocyte alkaline phosphatase score and the presence of

basophilia Basophilia is the condition of having greater than 200 basophils/μL in the venous blood. Basophils are the least numerous of the myelogenous cells, and it is rare for their numbers to be abnormally high without changes to other blood components. ...

were used to distinguish CML from a leukemoid reaction. However, at present the test of choice in adults to distinguish CML is an assay for the presence of the

Philadelphia chromosome The Philadelphia chromosome or Philadelphia translocation (Ph) is a specific genetic abnormality in Chromosome 22 (human), chromosome 22 of Leukemia, leukemia cancer cells (particularly chronic myeloid leukemia (CML) cells). This chromosome is defe ...

, either via

cytogenetics Cytogenetics is essentially a branch of genetics, but is also a part of cell biology/cytology (a subdivision of human anatomy), that is concerned with how the chromosomes relate to cell behaviour, particularly to their behaviour during mitosis ...

and

FISH Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% ...

, or via

PCR PCR or pcr may refer to: Science * Phosphocreatine, a phosphorylated creatine molecule * Principal component regression, a statistical technique Medicine * Polymerase chain reaction ** COVID-19 testing, often performed using the polymerase chain r ...

for the BCR/ABL fusion gene. The LAP (leukocyte alkaline phosphatase) score is high in reactive states but is low in CML. In cases where the diagnosis is uncertain, a qualified

hematologist Hematology ( always spelled haematology in British English) is the branch of medicine concerned with the study of the cause, prognosis, treatment, and prevention of diseases related to blood. It involves treating diseases that affect the produc ...

oncologist Oncology is a branch of medicine that deals with the study, treatment, diagnosis and prevention of cancer. A medical professional who practices oncology is an ''oncologist''. The name's etymological origin is the Greek word ὄγκος (''ó ...

should be consulted.

Treatment

Treatment of underlying condition. If drug induced, discontinue drug. If the reaction is found to be from anything besides drug use, certain anti neoplastic drugs may be indicated.

References

External links

{{Lymphoid malignancy, us=y Blood disorders

Causes

Diagnosis

Treatment

See also

References

External links