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Diagnosis of HES

An eosinophil is a type of white blood cell that plays an important role in the human immune system. For example, it helps us fight off certain types of infections like parasites. Many different problems can cause high numbers of eosinophils in the blood, including allergies, asthma, some gastrointestinal disorders, parasitic infection, some blood/bone marrow diseases, certain cancers, and other problems.


Photo courtesy of Dr. Margaret Collins
Normally, there are less than 5% eosinophils circulating in the blood vessels because they migrate quickly into the tissues and organs of the body. The highest concentration of eosinophils is usually found in the gastrointestinal tract. There is a complex series of chemical events that determine the levels of eosinophils in the blood and tissues. The proper balance and function of these events determines eosinophil production, their activity, and their time to die. When eosinophils occur in higher than normal numbers in the blood, without a known cause and for a sustained period of time (more than 6 months), an innate disorder of eosinophils may be present.

Eosinophil production is governed by several chemicals in blood called cytokines, including interleukin 3 (IL-3), interleukin 5 (IL-5), and granulocyte-macrophage colony-stimulating factor (GM-CSF). Cytokines have many functions. They mediate and regulate immunity, inflammation, and hematopoiesis (production of blood cells) and different cytokines are produced in high amounts in different diseases. IL-5 appears to be the most important and specific cytokine that is responsible for the production and activity of eosinophils. Cytokines bind to specific chemicals on the surface of cells, called membrane receptors. This binding initiates the cascade of changes in other chemicals inside the cell leading toward the change in cell’s behavior, including higher activity and multiplication. Many of the membrane receptors and intracellular chemicals belong to a class of chemicals called tyrosine kinases.

Hypereosinophilic Syndrome

HES is a group of disorders in which there are very high numbers of eosinophils found in the blood and tissue, for prolonged period of time for which a cause cannot be found. Continuous presence of high number of eosinophils in blood can eventually cause multiple organ tissue damage as these eosinophils infiltrate different tissues and cause inflammation. Unlike eosinophilic gastrointestinal disorders (EGID), which only affect the digestive tract, HES can affect any organ in the body, including the stomach and intestines, the heart, lungs, skin and other organs. The symptoms and prognosis in HES depends on the organ systems involved, disease severity and response to therapy. Outcomes can vary greatly from one person to the next. Your doctor can best answers questions about prognosis in HES on an individual basis.

Since many different problems can cause high numbers of eosinophils in the blood, higher than normal blood eosinophil number alone does not mean an individual has, or will develop, HES. Criteria has been developed that must be fulfilled for an individual to be diagnosed with HES.

Criteria for diagnosis of HES

  1. Peripheral blood eosinophilia (high numbers of eosinophils in the blood) more than 1500 eosinophils/ , for at least six months’ duration.
  2. End-organ (heart, lungs, GI tract, brain, skin, etc) involvement with eosinophil tissue infiltration (invasion) and injury.
  3. Exclusion of known other causes for the eosinophilia such as parasitic infections and certain bone marrow/blood diseases.

Tests are needed to diagnose HES and include a complete blood cell count, including eosinophil count, blood samples for liver and kidney function, and blood tests for Vitamin B12 and tryptase. Depending on symptoms and test results, other studies may be performed. For instance, ultrasound (echocardiography) is used to look at the function of the heart. A chest x-ray may be done to examine the lungs. A bone marrow biopsy is recommended in patients suspected of having HES. It commonly reveals high number of eosinophils and some other abnormalities, suggestive of an innate bone marrow/blood disease of eosinophils. Therefore, HES is classified as hematologic neoplasm (disease of the blood and bone marrow) and is part of the larger group of Myeloproliferative Neoplasms.

Closely related disease to HES is chronic eosinophilic leukemia (CEL). Major difference, in simple terms, is that in CEL all eosinophils found in the bone marrow and blood are proven to be identical (also called “clonal”, meaning that all originate from the same, one, abnormal eosinophil).

Bone marrow biopsy in Hypereosinophilic Syndrome, exhibiting a markedly increased number of eosinophils. This may happen with a number of disorders, including parasitic infection or Hypereosinophilic syndrome.

Page authored by: Srdan Verstovsek, MD, PhD, Leukemia Department, MD Anderson Cancer Center, Houston, TX

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© American Partnership for Eosinophilic Disorders (APFED) 2008-2013. All rights reserved.
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