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What Is a Leukemoid Reaction

Medically reviewed by Julie Scott, DNP, ANP-BC, AOCNP — By Daniel Yetman on October 20, 2022A leukemoid reaction is a very large short-term increase in your white blood cell count that can be mistaken for leukemia. Some of the potential causes include:infectionssolid cancersdrug side effects Leukemia is a group of cancers that develop in cells that produce blood cells in your bone marrow. People with leukemia often have extremely elevated white blood cell counts. Having a leukemoid reaction doesn’t mean you have cancer, but it can be a sign of a potentially serious medical condition that needs treatment. Read on to learn more about leukemoid reactions, including what they are and what causes them.

What is a leukemoid reaction

A leukemoid reaction is defined as a white blood cell count above 50,000 cells per microliter (µL) of blood. A microliter is one-millionth of a liter. For reference, the Leukemia & Lymphoma Society lists normal white blood count ranges as: Demographic White blood cells per microliter (µL) Men5,000–10,000Women (nonpregnant)4,500–11,000Children5,000–10,000 Bloodwork of a person with a leukemoid reaction usually shows an increase in mature neutrophils and immature granulocytes. These white blood cells play an important role in your immune system’s first-line defense. Neutrophils are the most common white blood cells in your bloodstream. They act as first responders to destroy bacteria and other foreign invaders. Granulocytes are released during infection and inflammatory conditions. They help destroy foreign invaders and signal for other white blood cells to attack them, too.

What s the difference between a leukemoid reaction and leukemia

A leukemoid reaction is an elevated white blood cell count caused by an underlying condition that isn’t a blood cancer. Leukemia is a group of blood cancers that form in the cells that create blood cells. A blood smear can help doctors or healthcare professionals understand which condition you have. During this test, your blood cells are examined microscopically to see how many white blood cells you have and whether they look abnormal. People with a type of leukemia called chronic myeloid leukemia often show an increase in abnormal granulocytes, whereas a leukemoid reaction is more likely to be characterized by an increase in mature neutrophils.

What are the different types of leukemoid reactions

Doctors can further classify a leukemoid reaction based on the elevated type of white blood cells.Granulocytic reaction: A granulocytic reaction is the most common type. It’s usually characterized by an increase in the number of neutrophils. It can be a sign of infection, some cancers, and other conditions.Lymphocytic reaction: A lymphocytic reaction is characterized by an increase in a group of white blood cells called lymphocytes. A lymphocytic reaction is often a sign of an immune reaction against cancer cells.Monocytic reaction: A monocytic reaction is an increase in white blood cells called monocytes. These cells multiply in response to infection or injury.

What are the symptoms of a leukemoid reaction

A leukemoid reaction is caused by an underlying condition. Symptoms vary depending on which underlying condition you have. Here’s a general look at how symptoms of some common causes compare to general symptoms of leukemia.LeukemiaInfectionCancerAlcohol hepatitisfever or chillsfever or chillsspecific organ symptomsfeverfatiguefatiguefatiguenausea or vomitingweaknesscoughskin changesdry mouthfrequent infectionssore throatchange in bowel habitsabdominal painunintentional weight lossdiarrhea or vomitingunintentional weight lossunintentional weight losseasy bleeding or bruisingabdominal painpoor wound healingeasy bleeding or bruisingswollen lymph nodesshortness of breathlump under skinjaundice

What causes a leukemoid reaction and who s at risk

A leukemoid reaction can be because of a variety of conditions that cause inflammation or stress in your body. Conditions that have been linked to leukemoid reactions include:sepsisorgan rejectionethylene glycol poisoningsolid cancersinfections such as:tuberculosisClostridioides difficilediphtheriadrugs such as corticosteroidssevere bleeding In a 2020 study published in the International Journal of Laboratory Hematology, researchers analyzed the underlying cause of 267 cases of white blood cell counts above 50,000 cells per µL of blood in Brazilian adults over a 2-year period. The researchers found that 60% of cases were caused by blood cancers. Of the 40% that made up leukemoid reactions:56% were caused by infection16% were caused by other solid cancers28% were caused by other conditions Small studies have reported leukemoid reactions in 1 to 4% of non-blood cancers. People with Down syndrome frequently have elevated white blood cell counts within the first few months of life that usually resolve themselves.

Can COVID-19 cause a leukemoid reaction

COVID-19 can affect many parts of your body, including causing changes in your white blood cell count. Low white blood cell counts have been reported more often than high blood cell counts in people with COVID-19, but several case studies report present people with leukemoid reactions. A 2021 case study reported a 36-year-old woman with severe COVID-19 who developed a leukemoid reaction presumed to be caused by COVID-19. The woman passed away 14 days after hospital admission. Another 2021 case study reported a 64-year-old woman with severe COVID-19 diagnosed with a leukemoid reaction. She died 13 days after hospital admission.

How is a leukemoid reaction diagnosed

A leukemoid reaction is diagnosed when you have a white blood cell count above 50,000 cells per µL of blood and don’t have blood cancer. Doctors can draw a sample of your blood and perform a complete blood cell count to measure your white blood cell count. Doctors can usually easily differentiate a leukemoid reaction from leukemia by performing a peripheral blood smear. A peripheral blood smear is a test where doctors look at your blood microscopically. A doctor may run a variety of other tests to rule out other conditions or find the underlying cause. Tests may include:other blood or urine testsphysical examimagingtissue biopsiesgenetic testing

How is a leukemoid reaction treated

A leukemoid reaction is treated by targeting the underlying condition that’s causing it. For example, a bacterial infection, such as tuberculosis, is treated with antibiotics. Underlying cancer may be treated with therapies such as:radiation therapychemotherapytargeted therapiesimmunotherapysurgery Alcohol hepatitis may be treated with:ceasing alcohol consumptionvitamin and nutrient supplementsliver transplantmedicationscounseling

What s the outlook for a person with a leukemoid reaction

The outlook for someone with a leukemoid reaction depends on the underlying cause. Blood cells usually return to normal levels when the underlying condition is treated. A highly elevated blood cell count may be a sign that an infection is advanced. In the 2020 study published in the International Journal of Laboratory Hematology,researchers found that people with leukemoid reactions associated with infections and cancers had poor outlooks.

Takeaway

A leukemoid reaction is a highly elevated white blood cell count caused by an underlying disease that isn’t a blood cancer. Many different conditions can cause a leukemoid reaction such as infections, alcohol hepatitis, and other cancers. A doctor can help you figure out why your white blood cell count is elevated by running blood and other tests. If the underlying cause is curable, your blood cell count will likely return to normal once it’s treated. Last medically reviewed on October 20, 2022

How we vetted this article

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ncbi.nlm.nih.gov/pmc/articles/PMC6982483/Gatt ME, et al. (2019). 78: Lymphoid leukemias. Clinical immunology: Principles and practice. St. Louis, MO: Elsevier.
sciencedirect.com/science/article/pii/B9780702068966000788Haruki K, et al. (2020). An integrated analysis of lymphocytic reaction, tumour molecular characteristics and patient survival in colorectal cancer.
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sciencedirect.com/topics/medicine-and-dentistry/leukemoid-reactionPortich JP, et al. (2020). Leukemoid reaction: A 21st-century cohort study.
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cureus.com/articles/52860-leukemoid-reaction-in-a-patient-with-severe-covid-19-infectionTargeted therapy to treat cancer. (2022).
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lls.org/treatment/lab-and-imaging-tests/understanding-blood-countsOur experts continually monitor the health and wellness space, and we update our articles when new information becomes available. Current Version Oct 20, 2022 By Daniel Yetman Edited By Willow Banks Medically Reviewed By Julie Scott, DNP, ANP-BC, AOCNP Copy Edited By Brennan Doherty Share this articleMedically reviewed by Julie Scott, DNP, ANP-BC, AOCNP — By Daniel Yetman on October 20, 2022

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