- Leukemoid reaction
Name = PAGENAME
DiseasesDB = 30101
ICD10 = ICD10|D|72|8|d|70
ICD9 = ICD9|288.62
MedlinePlus = 000575
MeshID = D007955The term leukemoid reaction, also referred to as transient myeloproliferative disorder, describes an elevated
white blood cellcount, or leukocytosis, that is a physiologic response to stress or infection (as opposed to a primary blood malignancy, such as leukemia).
Definition and diagnosis
Conventionally, a leukocytosis exceeding 50,000 WBC/mm3 with a significant increase in early
neutrophilprecursors is referred to as a leukemoid reaction. [cite book | author = Ronald Hoffman et al. | title = Hematology: basic principles and practice | publisher = Elsevier Churchill Livingstone | location = St. Louis, Mo | year = 2005 | id = ISBN 0-443-06628-0 p. 803.] The peripheral blood smear may show myelocytes, metamyelocytes, promyelocytes, and even myeloblasts; however, there is a mix of early mature neutrophil precursors, in contrast to the immature forms typically seen in acute leukemia. The bone marrowin 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 phosphatasescore and the presence of basophiliawere 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 cytogeneticsand FISH, or via PCRfor the Bcr/abl fusion protein. 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 hematologistor oncologistshould 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:
** Use of
** Use of
G-CSFor related growth factors
All-trans retinoic acid(ATRA)
* Infections (e.g.
* As a feature of
Trisomy 21in infancy (incidence of ~10%)
* As a
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