Hypereosinophilic (hy-per-ee-o-sin-o-FILL-ick) Syndrome (HES) is a group of rare blood disorders. It occurs when an individual’s blood has very high numbers of eosinophils. An eosinophil is a type of white blood cell that plays an important role in the immune system.
Most people have less than 500 eosinophils/microliter in their blood. People with HES usually have more than 1,500 eosinophils/microliter in their blood for 6 months or more, and the cause cannot be identified.
These eosinophils make their way into various tissues, causing inflammation and eventually organ dysfunction. The most commonly involved organs in HES include the skin, lungs, heart and nervous system.
Symptoms & Diagnosis
HES can happen at any age, although it is more common in adults. People with HES may suffer from a wide variety of symptoms, depending upon which parts of the body are affected.
These symptoms include:
- Skin rashes such as urticaria or angioedema
- Memory loss or confusion
- Shortness of breath
- Mouth sores
Symptoms of HES are also common in many other medical problems, making an initial diagnosis more difficult. The first step is to rule out other conditions with similar symptoms also associated with an elevated eosinophil count. Elevated eosinophil counts occur with parasitic infection, allergic disease, cancers, autoimmune diseases and drug reactions.
An allergist / immunologist has specialized training to effectively diagnose the problem and, if HES is present, to work collaboratively with other specialists such as a hematologist or cardiologist in the treatment and monitoring of HES.
Testing is individualized according to symptoms and may include stool evaluation to detect parasitic infection, allergy testing to diagnose environmental or food allergies, biopsies of the skin or other organs, blood tests to screen for autoimmunity or CT imaging of affected organs.
When diagnosed with HES, it is important to determine the extent of organ damage. A chest x-ray and echocardiogram are routinely performed to evaluate the heart and lungs. Other tests often performed in HES patients include liver and kidney function, serum vitamin B12 levels, erythrocyte sedimentation rate (ESR) to look for inflammation and serum tryptase levels.
Treatment & Management
The goal of HES treatment is to reduce eosinophil levels in the blood and tissues, thereby preventing tissue damage–especially in the heart. Standard HES treatment includes glucocorticosteroid medications such as prednisone, and chemotherapeutic agents such as hydroxyurea, chlorambucil and vincristine. Interferon-alpha may also be used as a treatment. This medication is administered by frequent injections.
Research is uncovering new treatment therapies for HES. One new approach for controlling malignant cell growth is the use of tyrosine kinase inhibitors such as Gleevec. Other tyrosine kinase inhibitors currently under study include Dasatinib and Nilotinib. Monoclonal antibody therapy has also shown promise for treatment of HES. Trial confirms long-term safety and efficacy of mepolizumab for HES.
The prognosis of HES depends upon the extent of any organ damage. In very severe cases, HES may be fatal, but there is hope. Survival rates have improved greatly. In 1975, only 12% of HES patients survived three years. Today, more than 80% of HES patients survive five years or more.