Eosinophilia-Myalgia Syndrome

Eosinophilia-myalgia syndrome (EMS) is a multisystem disease characterized by subacute onset of myalgias and peripheral eosinophilia, followed by chronic neuropathy and skin induration. An epidemic of EMS in 1989 was linked to l-tryptophan consumption originating from a single source. Following the US Food and Drug Administration ban on the sale of l-tryptophan, EMS incidence declined rapidly. Xenobiotic triggered acute inflammation in a genetically susceptible host likely mediates the early phase of EMS. Late in the disease, cytokine activation and upregulation of collagen and extracellular matrix genes may drive the sustained fibrotic response. The exact etiologic agent responsible for EMS remains unknown.