- Environmental pathology. Mast cell and eosinophil infiltration in intestinal mucosa of Lewis rats treated with L-tryptophan implicated in human eosinophilia myalgia syndrome. DeSchryver-Kecskemeti, K., Gramlich, T.L., Crofford, L.J., Rader, J.I., Page, S.W., Needham, L.L., Hill, R.H., Sternberg, E.M. Mod. Pathol. (1991)