The term leukemoid reaction describes an increased

white blood cell White blood cells (scientific name leukocytes), also called immune cells or immunocytes, are cells of the immune system that are involved in protecting the body against both infectious disease and foreign entities. White blood cells are genera ...

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; the term is most familiar as a characterization of cancer. A ''malignant'' tumor contrasts with a non-cancerous ''benign'' tumor in that a malignancy is not ...

, such as

leukemia Leukemia ( also spelled leukaemia; pronounced ) is a group of blood cancers that usually begin in the bone marrow and produce 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, lymphoid organs, lympha ...

myeloid Myeloid tissue, in the bone marrow sense of the word '' myeloid'' ('' myelo-'' + '' -oid''), is tissue of bone marrow, of bone marrow cell lineage, or resembling bone marrow, and myelogenous tissue (''myelo-'' + '' -genous'') is any tissue ...

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, ...

(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 an ...

** 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 vertebra ...

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. Function ...

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

Clostridioides difficile ''Clostridioides difficile'' ( syn. ''Clostridium difficile'') is a bacterium known for causing serious diarrheal infections, and may also cause colon cancer. It is known also as ''C. difficile'', or ''C. diff'' (), and is a Gram-positive spec ...

'' **

Tuberculosis Tuberculosis (TB), also known colloquially as the "white death", or historically as consumption, is a contagious disease usually caused by ''Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can al ...

Pertussis Whooping cough ( or ), also known as pertussis or the 100-day cough, is a highly contagious, vaccine-preventable bacterial disease. Initial symptoms are usually similar to those of the common cold with a runny nose, fever, and mild cough, bu ...

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 adu ...

(

lymphocyte A lymphocyte is a type of white blood cell (leukocyte) in the immune system of most vertebrates. Lymphocytes include T cells (for cell-mediated and cytotoxic adaptive immunity), B cells (for humoral, antibody-driven adaptive immunity), an ...

predominant) ** Visceral larva migrans (

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

predominant) * Asplenia *

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

* 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 (ischemia). Although uncommon in the general population, ischemic colitis occurs ...

* As a feature of

trisomy 21 A trisomy is a type of polysomy in which there are three instances of a particular chromosome, instead of the normal two. A trisomy is a type of aneuploidy (an abnormal number of chromosomes). Description and causes Most organisms that repro ...

in infancy (incidence of ~10%) * As a paraneoplastic phenomenon (rare)

Diagnosis

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

neutrophil Neutrophils are a type of phagocytic white blood cell and part of innate immunity. More specifically, they form the most abundant type of granulocytes and make up 40% to 70% of all white blood cells in humans. Their functions vary in differe ...

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 ...

s, metamyelocytes,

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 Cell nucleus, nucleus of a promyelocyte is approximately the ...

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 uncont ...

. Serum leukocyte

alkaline phosphatase The enzyme alkaline phosphatase (ALP, alkaline phenyl phosphatase, also abbreviated PhoA) is a phosphatase with the physiological role of dephosphorylating compounds. The enzyme is found across a multitude of organisms, prokaryotes and eukaryo ...

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 biological tissue, tissue found within the Spongy bone, 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 i ...

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; the term is most familiar as a characterization of cancer. A ''malignant'' tumor contrasts with a non-cancerous benign tumor, ''benign'' tumor in that a malig ...

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 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 an abnormal version of chromosome 22 where a part of the ''ABL (gene), Abelson murine leukemia'' 1 (''ABL1'') gene on chromosome 9 breaks off and attaches to the ''BCR (gene), break ...

, 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 an ...

and

FISH A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...

, or via PCR 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 ( 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 production ...

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 (''� ...

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