Animal models of the eosinophilia-myalgia syndrome

Shortly after the recognition of the eosinophilia-myalgia syndrome (EMS), several investigators did studies to replicate the cardinal features of this disorder in animals. These studies originally involved administration of both L-tryptophan (LT) and of specific compounds that were found in higher concentrations in lots of LT linked to the development of disease. Several of these studies claimed to represent an animal model of EMS because they reproduced some features of the human disease. However, a critical review of all the animal studies casts doubt on the validity of these assertions. These studies could generally not be reproduced and had methodologic flaws that limited extrapolation of results. Although the epidemiologic studies suggest that most cases of EMS were linked to ingestion of LT from a single manufacturer, the aggregate animal data in this area neither confirm nor rule out this hypothesis. The precise cause of EMS remains unknown.