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January 1, 1992

Eosinophilia-Myalgia Syndrome in L-Tryptophan—Exposed Patients

Author Affiliations

From the Centers for Disease Control, Public Health Service, US Department of Health and Human Services, Atlanta, Ga (Drs Kamb, Murphy, Nederlof, Horney, Swygert, Falk, and Kilbourne) and the Disease Control and Epidemiology Division, South Carolina Department of Health and Environmental Control, Columbia (Dr Jones). Dr Caston is in private practice in Spartanburg, SC.

JAMA. 1992;267(1):77-82. doi:10.1001/jama.1992.03480010085029

Objectives.  —To study the incidence of eosinophilia-myalgia syndrome, the risk factors associated with the syndrome, and the clinical spectrum of illness associated with L-tryptophan use in an exposed population.

Design.  —Retrospective cohort and nested case-control studies of risk factors for eosinophilia-myalgia syndrome using inpatient and outpatient chart reviews, telephone interviews, and in-person patient interviews. Descriptive study of clinical course of L-tryptophan users.

Setting.  —Office practice of one psychiatrist based in a small city (population 43467) in South Carolina.

Patients.  —Eligible subjects were all patients from the practice who used L-tryptophan during the 1989 study interval. Of these, 418 (87%) were interviewed.

Main Outcome Measures.  —Clinical spectrum of illness associated with L-tryptophan use, including definite and possible cases of eosinophilia-myalgia syndrome.

Results.  —Among the 418 interviewed L-tryptophan users, we identified 47 definite cases (11%) and 68 possible cases (16%) of eosinophilia-myalgia syndrome, most of which involved patients who were using one retail brand of L-tryptophan (brand A). Among the 157 brand A users, we identified 45 definite cases (29%) and 36 possible cases (23%) of eosinophilia-myalgia syndrome, and the risk for the syndrome increased as the brand A dose increased. Fifty percent (19 of 38) of those using more than 4000 mg/day developed definite eosinophilia-myalgia syndrome, and 84% (32 of 38) developed either definite or possible eosinophilia-myalgia syndrome. On multivariate analysis, risk for definite eosinophilia-myalgia syndrome was associated with brand A dose and age of the patient; however, gender, race, and use of other medications were not associated with the syndrome.

Conclusions.  —These results suggest that many people exposed to the agent causing eosinophilia-myalgia syndrome may develop illness, and dose of presumably contaminated L-tryptophan is the single most important predictor of eosinophilia-myalgia syndrome. The broad range of signs and symptoms reported by patients using L-tryptophan illustrates that a strict case definition may identify only about half of those affected.(JAMA. 1992;267:77-82)