Eosinophilia caused by administration of L-tryptophan to animals with adrenal dysfunction

We have investigated an animal model of eosinophilia-myalgia syndrome (EMS), a disease that occurred in various parts of the United States in 1989, with a view to determining its cause. We speculated that adrenal dysfunction might have potentially contributed to the occurrence of EMS and studied the effects of adrenal dysfunction on the eosinophil count in peripheral blood by using rats and mice whose adrenals had been excised or that had been metyrapone-treated, and giving them L-tryptophan. As a result, a significant increase in the eosinophil count was observed in both animal species. The results suggest that EMS may have been caused, not by L-tryptophan alone, but by the combined effects of adrenal dysfunction and L-tryptophan ingestion.