Hypereosinophilic Syndrome

Hypereosinophilic (pronounced “hy-per-ee-oh-sin-oh-fill-ick”) syndrome (HES) is a rare group of conditions that involve persistent high levels of white blood cells called eosinophils. Eosinophils protect your body from parasitic infections and respond to allergens.

Normally, you have about 100 to 500 eosinophils per microliter of blood. That level may increase when your body makes more eosinophils in response to a threat. But with HES, you have extremely high levels — 1,500 or more per microliter.

The eosinophil overload can lead to lasting inflammation that can damage your organs (usually your skin, lungs, gut, heart or nervous system). Left untreated, hypereosinophilic syndrome can be fatal. But with prompt treatment, more than 8 out of 10 people are alive five years after their diagnosis.

Anyone can develop HES, but it’s most common in adults between 20 and 50. Some varieties of HES are more common in males.

Symptoms of hypereosinophilic syndrome

The most common symptom is a rash. You may also experience fatigue, a fever and unexplained weight loss. For the most part, symptoms depend on the location of the damage. HES symptoms may include:

• An itchy rash resembling eczema or hives
• Belly pain, nausea and diarrhea
• Brain fog and numbness and tingling on one or both sides of your body
• Chest pain and heart palpitations
• Cough, wheezing and shortness of breath

Hypereosinophilic syndrome causes

Doctors don’t know all the factors that trigger the increase in eosinophils. Some possible causes are:

• Gene changes (mutations) that happen over time: The mutations can cause your body to make too many eosinophils. Conditions associated with HES that involve mutations include myeloproliferative neoplasms.
• Gene changes you’re born with: You may inherit a gene variation from a biological parent that causes hypereosinophilia. Doctors call this familial HES.
• Blood cells that release too much interleukin-5 (IL-5): Abnormal T cells (a type of white blood cell) may release too many cytokines. These proteins activate eosinophils.
• Untreated conditions: Untreated infections, allergies, cancer or other conditions can lead to hypereosinophilia.

Sometimes, despite a thorough workup, healthcare providers can’t identify the cause. Those cases are called idiopathic HES. This can happen in up to 3 out of 4 people.

Complications of this condition

Without treatment, eosinophils can build up in an organ. Eventually, they can cause it to stop working. Most people who die from HES do so because of heart damage that leads to heart failure.

HES can also increase your risk of serious blood clots. Depending on the cause, HES can progress to blood cancers like leukemia and lymphoma. But this is uncommon.

How doctors diagnose hypereosinophilic syndrome

Healthcare providers use a process of elimination to diagnose HES. For example, if you have a persistent itchy rash, your healthcare provider would likely check for certain skin disorders. They’d prescribe treatments for those first.

If you’re still having symptoms, your provider might test your eosinophil levels. With HES, your levels should be greater than 1,500 or more per microliter on at least two different occasions. Usually, there are also signs of organ damage. You may need a biopsy of that organ to check for damage.

Tests for hypereosinophilic syndrome

These tests check for:

• Substances in your blood that signal organ damage
• Signs of organ or tissue damage in your chest, abdomen or pelvis (usually involves getting a CT scan or endoscopies)
• Issues with how your lungs are working (pulmonary function tests)
• Issues with how your heart is working (electrocardiograms and echocardiograms)
• Abnormal blood cells that may be causing HES (bone marrow biopsy)
• Abnormal genes associated with HES (genetic tests)

How is hypereosinophilic syndrome treated?

Treatments focus on reducing the high eosinophil levels in your blood and tissues. Usually, this involves medications. If your condition is linked to a specific cause, your healthcare provider will choose treatments designed to address it. Standard treatment includes:

• Corticosteroids, like prednisone
• Chemotherapy drugs, like hydroxyurea and vincristine
• Targeted therapy drugs, like imatinib
• Immunotherapy, like interferons, or antibody therapy, like mepolizumab

If medications don’t work, you may need a stem cell transplant. This procedure replaces faulty stem cells that give rise to too many eosinophils with healthy ones from a donor. This is a potential cure for HES, but not everyone’s a candidate. It also carries a high risk of complications.

When should I see my healthcare provider?

Your provider will monitor you regularly if you have HES. How often you’ll need tests to check your eosinophils depends on how serious your condition is. It also depends on what medicines you’re taking. They can cause side effects. If you’re having them, your provider needs to know.

Contact your healthcare provider if your symptoms persist or get worse. Go to the emergency room if you’re experiencing symptoms of organ damage or major clots. Symptoms include:

• Chest pain
• Diarrhea
• Fainting or dizziness
• Headache or confusion
• Nausea and sudden or excessive sweating
• Sudden vision changes

What can I expect if I have hypereosinophilic syndrome?

Your prognosis, or expected outcome, depends on your situation. Usually, the sooner you receive HES treatment, the less likely you are to have lasting problems.

In the past, it was rare for people with HES to live past three years after diagnosis. But with better tests to diagnose HES and newer treatments, most people are living longer. More than 8 out of 10 people with HES are still alive five years after their diagnosis. Depending on what’s causing your HES, some medications can put HES in remission. This means you have no signs or symptoms of disease.

Is there anything I can do to feel better?

Hypereosinophilic syndrome can vary in severity and causes. It can be tough to understand what this diagnosis means for your future.

Lean on your healthcare provider as much as you can to learn about your diagnosis. Don’t hesitate to ask your healthcare provider what’s likely causing your high levels. Ask what results you can expect from treatment. They can also tell you what daily adjustments you’ll need to make to manage this condition.