Eosinophilia-myalgia syndrome is a rare disorder that affects multiple organ systems of the body including the muscles, skin, and lungs. The onset of the disorder is often abrupt and the specific symptoms can vary greatly from one person to another. Common symptoms include muscle pain (myalgia), muscle weakness, cramping, skin rashes, difficulty breathing (dyspnea) and fatigue. Affected individuals have elevated levels of certain white blood cells known as eosinophils in the various tissues of the body, a condition known as eosinophilia. Eosinophilia-myalgia syndrome can potentially cause severe, disabling complications and even death.
The eosinophilia-myalgia syndrome occurred as an epidemic in 1989 and occurrence of the syndrome was traced to L-tryptophan produced by one Japanese company, Showa Denko KK. Most individuals who developed eosinophilia-myalgia syndrome had ingested contaminated L-tryptophan, a dietary amino acid supplement often sold in health food stores before being pulled from the market in 1990. However, contaminated L-tryptophan does not account for all cases of eosinophilia-myalgia syndrome suggesting that other environmental agents may cause the disorder. Very few cases of EMS have been identified since the 1989 epidemic.