The eosinophilia-myalgia syndrome with neuritis associated with L-tryptophan use.

Causes of the eosinophilia-myalgia syndrome other than L-tryptophan include parasitic myositis (that is, trichinosis), acute tropical myositis, sarcoidosis, granulomatous myositis, polymyositis, collagen vascular diseases, neoplastic myositis, and eosinophilic myositis. Some of these can be excluded by the absence of associated findings, that is, sarcoidosis, collagen vascular disease, neoplastic myositis; or on epidemiologic grounds, for example, acute tropical myositis. A muscle biopsy is diagnostic for trichinosis and for granulomatous, neoplastic, and eosinophilic myositis. A normal erythrocyte sedimentation rate militates against but does not rule out neoplastic or collagen vascular disease-associated myositis. The erythrocyte sedimentation rate may be elevated in most of these disorders although trichinosis is characterized by a very low rate. Most conditions associated with eosinophilia are characterized by both blood and local tissue eosinophilia.