What Is Eosinophilia-Myalgia Syndrome?

Eosinophilia-myalgia syndrome (EMS) is a rare disorder in which white blood cells known a eosinophils build up in the body, causing inflammation in different areas including the muscles, skin, and lungs. Eosinophilia-myalgia syndrome can cause symptoms like itchy rash, fatigue, and joint pain, but also serious complications like irregular heartbeat and memory issues. It can even be fatal.

There is no test for EMS, so it may be misdiagnosed as a condition with similar symptoms such as fibromyalgia or lupus. And while eosinophilia-myalgia syndrome has long been linked to L-tryptophan—an amino acid available in supplement form, the disorder has also been diagnosed in people without a history of using these products.

This article explains EMS and its symptoms, as well as its potential causes. It also discusses how eosinophilia-myalgia syndrome is diagnosed and the treatment options.

Causes of Eosinophilia-Myalgia Syndrome

Eosinophilia-myalgia syndrome (EMS) first emerged in the United States in October 1989, when three women in New Mexico sought treatment for similar symptoms. These women had all taken the same brand of an L-tryptophan health supplement.

L-tryptophan naturally occurs in certain foods, but it was the synthetic L-tryptophan products that were linked to the symptoms of severe muscle pain with elevated eosinophil levels.

Ultimately, there were 37 deaths and more than 1,500 illnesses among people who took the supplement for stress, depression, premenstrual syndrome (PMS), and other reasons. In 1990, the Food and Drug Administration recalled all L-tryptophan supplements because of the link to EMS.

After 1994, however, synthetic L-tryptophan was again legal to sell and manufacture in the U.S. Since then, the National Institutes of Health (NIH) has warned of other eosinophilia-myalgia syndrome cases associated with the supplement 5-HTP, which is chemically similar to L-tryptophan and should be used with caution.

Symptoms of EMS

The most common symptom of eosinophilia-myalgia syndrome is generalized, severe muscle pain that tends to worsen over weeks and may cause muscle spasms. Symptoms tend to begin suddenly and range from mild to severe. The condition can cause life-threatening complications and may result in death.

Eosinophilia-myalgia syndrome goes through acute and chronic phases that share symptoms of muscle pain and fatigue. The acute phase may last anywhere between three and six months, with common symptoms of skin changes and muscle pain in the arms and legs.

The skin of those affected may swell, thicken, or harden as they develop eosinophilic fasciitis. People who have this condition over a long time may also develop impaired function in affected joints.

During the chronic phase, symptoms appear to flare. They may act up for a period of time and then go into remission. Overall symptoms of eosinophilia-myalgia syndrome in this phase include:

• Swelling of the arms and legs, and sometimes the face
• Joint pain
• An extremely itchy skin rash
• A cough and shortness of breath
• Fatigue
• Fever
• Patchy hair loss (alopecia)
• Bladder issues
• Behavioral changes (irritability, mood changes)
• Cognitive difficulties (memory issues, trouble concentrating)
• Digestive issues (nausea, vomiting, cramping)
• Heart abnormalities (inflammation, irregular heartbeat)

Digestive and cardiac issues are more likely to occur during this phase as well.

How is Eosinophilia-Myalgia Syndrome Diagnosed?

The eosinophilia-myalgia syndrome diagnosis is difficult, and there are no available tests used to confirm EMS. The criteria established by the Centers for Disease Control and Prevention (CDC) in the wake of cases linked to L-tryptophan use include:

• A blood draw with eosinophil counts of 1,000 cells or more per cubic millimeter (mm3)
• Severe muscle pain that limits daily activities
• Exclusion of any infection or other cause of the pain with elevated eosinophils

In addition to conducting a physical exam and running blood tests, your healthcare provider must consider all factors related to your personal health history, especially medication use. Drugs are the most common cause for persistent eosinophilia in the developed world.

What Drugs Can Cause Eosinophilia?

Among the drugs known to raise eosinophil levels are:

• Antibiotics (penicillin, cephalosporins)
• Non-steroidal anti-inflammatory medications (aspirin, ibuprofen)
• Anti-seizure drugs (phenytoin)
• Gout medication (allopurinol)

More rarely a severe form of response occurs, called drug reaction with eosinophilia and systemic symptoms (DRESS). Antibiotics and anti-seizure drugs, as well as antivirals used to treat human immunodeficiency virus (HIV) infection, are most often linked to serious DRESS episodes.

Your healthcare provider will need to rule out any drug response as part of an EMS diagnosis.

Treatment

There is no evidence-based standard of care for eosinophilia-myalgia syndrome that's been fully researched and adopted by medical professions. For this reason, treatment is tailored to each individual.

Among the medications used to treat symptoms of eosinophilia-myalgia syndrome are:

• Muscle relaxants
• Pain relievers
• Diuretic drugs to reduce fluid retention
• Corticosteroid drugs to reduce inflammation

A Word From Verywell

Because eosinophilia-myalgia syndrome is a chronic illness, people living with the condition may need to make lifestyle changes that can help. While little is known about long-term impacts and life expectancy, staying as physically active as possible appears to offer some benefits. Be sure to discuss diet, exercise, and other lifestyle changes with your healthcare provider.