Post-epidemic eosinophilia-myalgia syndrome associated with L-tryptophan

Eosinophilia-myalgia syndrome (EMS) is 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 consumption of L-tryptophan that had originated from a single source. Following the ban by the Food and Drug Administration (FDA) on the sale of L-tryptophan, the incidence of EMS declined rapidly. Moreover, no new cases have been described since the FDA ban was lifted in 2005. We report the clinical, histopathologic, and immunogenetic features of a new case of L-tryptophan-associated EMS, along with evidence of activated transforming growth factor β and interleukin-4 signaling in the lesional skin.