Leukemoid reaction
Encyclopedia
The term leukemoid reaction describes an elevated white blood cell
count, or leukocytosis
, that is a physiological response to stress or infection (as opposed to a primary blood malignancy
, such as leukemia
).
It may be lymphoid
or myeloid
.
s, metamyelocyte
s, promyelocyte
s, and rarely myeloblasts; however, there is a mix of early mature neutrophil precursors, in contrast to the immature forms typically seen in acute leukemia
. Serum leukocyte alkaline phosphatase
is elevated in leukemoid reaction, but is depressed in chronic myelogenous leukemia
. The bone marrow
in a leukemoid reaction, if examined
, may be hypercellular but is otherwise typically unremarkable.
Leukemoid reactions are generally benign and are not dangerous in and of themselves, although they are often a response to a significant disease state (see Causes below). However, leukemoid reactions can resemble more serious conditions such as chronic myelogenous leukemia
(CML), which can present with identical findings on 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
, either via cytogenetics
and FISH
, 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 or oncologist should be consulted.
White blood cell
White blood cells, or leukocytes , are cells of the immune system involved in defending the body against both infectious disease and foreign materials. Five different and diverse types of leukocytes exist, but they are all produced and derived from a multipotent cell in the bone marrow known as a...
count, or leukocytosis
Leukocytosis
Leukocytosis is a raised white blood cell count above the normal range in the blood. It is frequently a sign of an inflammatory response, most commonly the result of infection, and is observed in certain parasitic infections...
, that is a physiological response to stress or infection (as opposed to a primary blood malignancy
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
, such as leukemia
Leukemia
Leukemia or leukaemia is a type of cancer of the blood or bone marrow characterized by an abnormal increase of immature white blood cells called "blasts". Leukemia is a broad term covering a spectrum of diseases...
).
It may be lymphoid
Lymphoid
Lymphoid is a term used to describe lymph or the lymphatic system.In the context of lymphoid leukemia, it refers specifically to lymphocytes Lymphoid leukemias and lymphomas are now considered to be tumors of the same type of cell lineage. They are called "leukemia" when in the blood or marrow and...
or myeloid
Myeloid
The term myeloid suggests an origin in the bone marrow or spinal cord, or a resemblance to the marrow or spinal cord.In hematopoiesis, the term "myeloid cell" is used to describe any leukocyte that is not a lymphocyte...
.
Definition and diagnosis
Conventionally, a leukocytosis exceeding 50,000 WBC/mm3 with a significant increase in early neutrophil precursors is referred to as a leukemoid reaction. The peripheral blood smear may show myelocyteMyelocyte
A myelocyte is a young cell of the granulocytic series, occurring normally in bone marrow, but not in circulating blood .-Histology:...
s, metamyelocyte
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...
s, promyelocyte
Promyelocyte
A promyelocyte is a granulocyte precursor, developing from the myeloblast and developing into the myelocyte.-External links: - "18. Bone Marrow and Hemopoiesis: bone marrow smear, promyelocyte and erythroblasts " "Bone marrow" "Bone marrow"* - "Bone marrow smear"...
s, and rarely myeloblasts; however, there is a mix of early mature neutrophil precursors, in contrast to the immature forms typically seen in acute leukemia
Acute leukemia
Acute leukemia or acute leukaemia is a generic term used to describe a family of serious medical conditions relating to an original diagnosis of leukemia...
. Serum leukocyte alkaline phosphatase
Alkaline phosphatase
Alkaline phosphatase is a hydrolase enzyme responsible for removing phosphate groups from many types of molecules, including nucleotides, proteins, and alkaloids. The process of removing the phosphate group is called dephosphorylation...
is elevated in leukemoid reaction, but is depressed in chronic myelogenous leukemia
Chronic myelogenous leukemia
Chronic myelogenous leukemia , also known as chronic granulocytic leukemia , is a cancer of the white blood cells. It is a form of leukemia characterized by the increased and unregulated growth of predominantly myeloid cells in the bone marrow and the accumulation of these cells in the blood...
. The bone marrow
Bone marrow
Bone marrow is the flexible tissue found in the interior of bones. In humans, bone marrow in large bones produces new blood cells. On average, bone marrow constitutes 4% of the total body mass of humans; in adults weighing 65 kg , bone marrow accounts for approximately 2.6 kg...
in a leukemoid reaction, if examined
Bone marrow biopsy
Bone marrow examination refers to the pathologic analysis of samples of bone marrow obtained by bone marrow biopsy and bone marrow aspiration. Bone marrow examination is used in the diagnosis of a number of conditions, including leukemia, multiple myeloma, lymphoma, anemia, and pancytopenia...
, may be hypercellular but is otherwise typically unremarkable.
Leukemoid reactions are generally benign and are not dangerous in and of themselves, although they are often a response to a significant disease state (see Causes below). However, leukemoid reactions can resemble more serious conditions such as chronic myelogenous leukemia
Chronic myelogenous leukemia
Chronic myelogenous leukemia , also known as chronic granulocytic leukemia , is a cancer of the white blood cells. It is a form of leukemia characterized by the increased and unregulated growth of predominantly myeloid cells in the bone marrow and the accumulation of these cells in the blood...
(CML), which can present with identical findings on peripheral blood smear.
Historically, various clues including the leukocyte alkaline phosphatase score and the presence of basophilia
Basophilia
Basophilia is a condition where the basophil quantity is abnormally elevated .-Causes:Basophilia as an isolated finding is uncommon. However it is a common feature of myeloproliferative disorders and particularly prominent in chronic myelogenous leukemia....
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
Philadelphia chromosome
Philadelphia chromosome or Philadelphia translocation is a specific chromosomal abnormality that is associated with chronic myelogenous leukemia . It is the result of a reciprocal translocation between chromosome 9 and 22, and is specifically designated t...
, either via cytogenetics
Cytogenetics
Cytogenetics is a branch of genetics that is concerned with the study of the structure and function of the cell, especially the chromosomes. It includes routine analysis of G-Banded chromosomes, other cytogenetic banding techniques, as well as molecular cytogenetics such as fluorescent in situ...
and FISH
Fluorescent in situ hybridization
FISH is a cytogenetic technique developed by biomedical researchers in the early 1980s that is used to detect and localize the presence or absence of specific DNA sequences on chromosomes. FISH uses fluorescent probes that bind to only those parts of the chromosome with which they show a high...
, 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 or oncologist should be consulted.
Causes of leukemoid reaction
As noted above, a leukemoid reaction is typically a response to an underlying medical issue. Causes of leukemoid reactions include:- Hemorrhage
- Drugs
- Use of Sulfa drugs
- Use of DapsoneDapsoneDapsone is a medication most commonly used in combination with rifampicin and clofazimine as multidrug therapy for the treatment of Mycobacterium leprae infections . It is also second-line treatment for prophylaxis against Pneumocystis pneumonia caused by Pneumocystis jiroveci Dapsone...
- Use of glucocorticoidGlucocorticoidGlucocorticoids are a class of steroid hormones that bind to the glucocorticoid receptor , which is present in almost every vertebrate animal cell...
s - Use of G-CSF or related growth factors
- All-trans retinoic acid (ATRA)
- Infections
- Clostridium difficileClostridium difficileClostridium difficile , also known as "CDF/cdf", or "C...
- TuberculosisTuberculosisTuberculosis, MTB, or TB is a common, and in many cases lethal, infectious disease caused by various strains of mycobacteria, usually Mycobacterium tuberculosis. Tuberculosis usually attacks the lungs but can also affect other parts of the body...
- PertussisPertussisPertussis, also known as whooping cough , is a highly contagious bacterial disease caused by Bordetella pertussis. Symptoms are initially mild, and then develop into severe coughing fits, which produce the namesake high-pitched "whoop" sound in infected babies and children when they inhale air...
- Infectious mononucleosisInfectious mononucleosisInfectious mononucleosis is an infectious, widespread viral...
(lymphocyteLymphocyteA lymphocyte is a type of white blood cell in the vertebrate immune system.Under the microscope, lymphocytes can be divided into large lymphocytes and small lymphocytes. Large granular lymphocytes include natural killer cells...
predominant) - Visceral Larva Migrans (eosinophil predominant)
- Clostridium difficile
- AspleniaAspleniaAsplenia refers to the absence of normal spleen function and is associated with some serious infection risks. Hyposplenism is used to describe reduced splenic functioning, but not as severely affected as with asplenism.-Congenital:...
- Diabetic ketoacidosisDiabetic ketoacidosisDiabetic ketoacidosis is a potentially life-threatening complication in patients with diabetes mellitus. It happens predominantly in those with type 1 diabetes, but it can occur in those with type 2 diabetes under certain circumstances...
- Organ necrosis
- Hepatic necrosis
- Ischemic colitisIschemic colitisIschemic 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 frequency in the elderly, and is the most common form of bowel ischemia...
- As a feature of Trisomy 21 in infancy (incidence of ~10%)
- As a paraneoplastic phenomenon (rare)
See also
- NeutrophiliaNeutrophiliaNeutrophilia is a condition where a person has a high number of neutrophil granulocytes in their blood.-Causes:...
- LeukocytosisLeukocytosisLeukocytosis is a raised white blood cell count above the normal range in the blood. It is frequently a sign of an inflammatory response, most commonly the result of infection, and is observed in certain parasitic infections...
- Leukemid