Environmental pathology. Mast cell and eosinophil infiltration in intestinal mucosa of Lewis rats treated with L-tryptophan implicated in human eosinophilia myalgia syndrome.

A recently developed animal model for the L-tryptophan-associated eosinophilia myalgia syndrome was used to examine the small intestine and colon, because there is clinical involvement at these sites in patients. Increased perivascular inflammatory infiltrates rich in degranulating mast cells, eosinophils, and monocytes were seen in the lamina propria of experimental animals when compared with controls. L-Tryptophan-associated disease also shares many clinical features with idiopathic scleroderma/eosinophilic fasciitis, in which there is gastrointestinal involvement as well. These features are similar to those found in the recently described animal model. The apparent morphologic and clinical similarities between these entities suggest that the animal model is suitable for further studying the pathogenesis of the gastrointestinal involvement in all these diseases.