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.


Early symptoms of HES may include fatigue, cough, breathlessness, muscle pain, rash and fever.


Some varieties of hypereosinophilic syndrome tend to run in families. Other types have been associated with certain types of cancers, infections or other health problems.

Risk factors

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


Many types of disorders can raise your eosinophil level, including certain infections, allergies and reactions to medications. When trying to determine whether you have hypereosinophilic syndrome (HES), your doctor is likely to ask about your travel history and any medications you're taking, to help rule out these other causes.

Laboratory tests

Your doctor may also need information from some of the following lab tests:

  • 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
  • Genetic test, to check for a gene mutation that can cause HES

Imaging tests

Imaging tests may include:

  • X-rays, to check the condition of your lungs
  • CT scan, to detect problems in the chest, abdomen and pelvis
  • Echocardiogram or MRI, to assess heart function


Treatment for hypereosinophilic syndrome 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.

If you have no symptoms and your eosinophil count is low enough, you might require no treatment other than close monitoring for any changes related to HES.


Systemic corticosteroids, such as prednisone, are the first line treatment. Other treatment options include:

  • Hydroxyurea (Droxia, Hydrea, Siklos)
  • Imatinib (Gleevec)
  • Vincristine

Because HES can increase your risk of blood clots, you might also be prescribed blood-thinning medications such as warfarin (Coumadin).

Surgery and other procedures

If nothing else has worked, your doctor might suggest a stem cell or bone marrow transplant.

Preparing for an appointment

You'll likely first bring your symptoms to the attention of your family doctor. Depending on your symptoms, you may be referred to specialists in blood diseases (hematology), heart conditions (cardiology) or allergies.

Consider taking a relative or friend along to the appointment to help remember all the information provided.

Here's some information to help you get ready for the appointment, and what to expect from the doctor.

What you can do

Before your appointment, make a list of:

  • Signs and symptoms, including any that seem unrelated to the reason for the appointment
  • Any medications, including vitamins, herbs and over-the-counter medicines that you're taking, and their dosages
  • Key personal information, including any major stresses or recent changes in your life

For hypereosinophilic syndrome, some basic questions to ask the doctor include:

  • Will I need additional tests?
  • What are the treatment options?
  • What are the benefits and risks of each treatment?
  • Should I see additional specialists? What will that cost, and will my insurance cover it?
  • Are there brochures or other printed material that I can have? What websites do you recommend?

What to expect from your doctor

The doctor is likely to ask you several questions. Be ready to answer them to allow time later to cover other points you want to address. Examples include:

  • When did you first begin experiencing symptoms?
  • Are the symptoms continuous or occasional?
  • How severe are the symptoms?
  • What, if anything, seems to improve your symptoms?
  • What, if anything, appears to worsen the symptoms?
  • Have you traveled out of the country lately?
  • Do you have any allergies or skin conditions?
  • Have you been exposed to any parasites such as hookworm?

Content From Mayo Clinic Updated: 04/26/2022
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