Hypereosinophilic Syndrome

Eosinophils are the type of white blood cells that play a vital role in the body’s immune mechanisms. Hypereosinophilic Syndrome (HES) is a group of rare blood disorders. We have less than 500 eosinophils/microliter in our blood. But in case of HES the eosinophil count will be more than 1,500 eosinophils /microliter.

When the eosinophil count is more in the blood, they make their way to different tissues of the body, which leads to inflammation and ultimately organ dysfunction. The most commonly affected organs include lungs, heart, skin, and nervous system.

Subtypes of HES

There are two subtypes of HES:

Myeloproliferative variant: this type of HES is associated with a small interstitial deletion in the chromosome 4. The patient often has anemia, thrombocytopenia, splenomegaly, myelofibrosis, elevations in the serum vitamin B12 levels.

Lymphoproliferative variant: this type of HES is associated with a clonal population of T cells with aberrant phenotype. Patients with this subtype often experience skin abnormalities, angioedema, and hypergammaglobulinemia, and serum sickness.


HES have no clear cause. It results from certain types of cancer, such as bone marrow or lymph node cancer. It is also caused by parasitic and fungal infections, toxins, skin disorders, endocrine disorders, etc.


HES is more common in adults. However, it can occur at any age. Some of the common symptoms of HES include:

  • Fever
  • Cough
  • Fatigue
  • Skin rash
  • Dizziness
  • Confusion
  • Mouth sores


Your doctor will diagnose the HES by ruling out the secondary causes and clonal eosinophilia. The doctor will take the medication history and performs a thorough examination. An immunologist would effectively diagnose the problem and collaboratively work with specialists such as hematologist or cardiologist in treating and monitoring the HES.

The diagnostic testing is specific according to your symptoms which may include evaluating the stool for detecting the parasite, allergy testing, biopsies of skin or other organs, blood tests for screening autoimmunity or CT scanning of the affected organs.

If you are diagnosed with HES, your doctor would determine the extent of organ damage, for this, a chest X-ray and echocardiogram (ECG) are performed for evaluating your lungs and heart. Your doctor will also perform certain tests to evaluate your liver and kidney functioning. Erythrocyte sedimentation rate is performed to find out the presence of infection in the body.


The main goal of the treatment for HES is to reduce the tissue and blood eosinophils, to monitor and restrict the organ damage.

Your doctor would prescribe corticosteroids as first-line drugs- ex: Prednisolone along with hydroxyurea. Interferon alpha is given as a second-line drug. If both these drugs fail to act then, your doctor will prescribe monoclonal antibodies such as mepolizumab and alemtuzumab which can be successful.

In the case of refractory HES, your doctor would recommend allogeneic hematopoietic cell transplantation. Other treatment measures would include anticoagulation therapy and agents that give symptomatic relief (opiates, histamines). The rest of the treatment will depend on the organs involved- ex: diuretics in cardiac failure.