Hypereosinophilic syndrome


Hypereosinophilic (hy-per-ee-o-SIN-o-phil-ik) syndrome (HES) is a group of blood disorders that occur when you have high numbers of eosinophils — white blood cells that play an important role in your immune system. Over time, the excess eosinophils enter various tissues, eventually damaging your organs.

The most common targets are the skin, lungs, digestive tract, heart, blood and nervous system. Untreated, HES can become life-threatening.

HES can affect anyone. But it occurs more often in men, usually between the ages of 20 and 50.


Symptoms vary, depending on what part of your body is affected. Skin signs and symptoms include itching and rashes. If your lungs are affected, you may be short of breath and have a cough.


Many types of disorders can raise your eosinophil level, including certain infections, allergies and reactions to medications. Your doctor is likely to ask about your travel history and any medications you're taking, to help rule out these other causes of your high eosinophil count.

You are also likely to have:

  • Blood tests, to detect autoimmune conditions, parasitic infections, or problems with your liver or kidneys
  • Allergy tests, to detect environmental or food allergies
  • Stool tests, to detect parasitic infections such as hookworm
  • Imaging tests, to help evaluate the condition of your heart, abdomen and lungs

Determining the cause of HES

If you've been diagnosed with HES, you might have tests to help determine the cause. These tests can include:

  • Blood screening. Your blood can be tested for a genetic mutation known as FIP1L1-PDGFRA, which can cause HES.
  • Bone marrow biopsy. A sample of bone marrow is taken for analysis in the laboratory. Biopsy might be recommended to exclude the possibility of other conditions, if you don't have a genetic mutation that causes HES.


Treatment for HES is aimed at reducing your eosinophil count to prevent tissue damage, especially to your heart. Specific treatment depends on your symptoms, the severity of your condition and the cause of your HES.

Your doctor might recommend:

  • Watchful waiting. If you have no symptoms and your eosinophil count is low enough, you might be closely monitored for any changes related to HES.
  • Prednisone. People who don't have the FIP1L1-PDGFRA gene mutation are usually first treated with this corticosteroid. If prednisone lowers your eosinophil count, your doctor might then prescribe nonsteroidal immune-suppressing medications, to avoid long-term use of steroids. Prednisone side effects can include mood swings, high blood pressure and increased risk of infections.
  • Protein-tyrosine kinase inhibitor. If you have the FIP1L1-PDGFRA gene mutation, you have a condition known as chronic eosinophilic leukemia. Treatment with imatinib (Gleevec) — a protein-tyrosine kinase inhibitor medication — slows the growth of cancer cells. Most people treated with imatinib achieve remission.

Last Updated Jun 20, 2017

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