The clinical spectrum of the eosinophilia-myalgia syndrome associated with L-tryptophan ingestion: Clinical features in 20 patients and aspects of pathophysiology

We describe the clinical spectrum of the L-tryptophan-associated eosinophilia-myalgia syndrome in 20 patients. In all but one case, patients met the Centers for Disease Control (CDC) case definition for the syndrome: peripheral blood eosinophilia (eosinophil count > 1.0 × 10⁹/L) and generalized, disabling myalgias without other recognized causes. Three patients with eosinophilia and myalgia developed eosinophilic fasciitis, and 4 other patients developed, respectively, pneumonitis and myocarditis, neuropathy culminating in respiratory failure, encephalopathy, and fibrosis about the common bile duct. No relation was apparent between dose or duration of L-tryptophan exposure and the eosinophilia-myalgia syndrome. No organic contaminants were identified in L-tryptophan preparations taken by patients or asymptomatic users when these preparations were examined by chromatography or mass spectroscopy. Biopsy specimens in 12 patients showed a mononuclear exudate with a variable admixture of eosinophils in affected tissues, including skin, fascia, muscle, and some viscera. Eosinophil toxic granule proteins, major basic protein, and eosinophilderived neurotoxin were elevated in the serum and urine of patients compared with normal control subjects (P < 0.01 and P < 0.02, respectively). Immunofluorescence showed major basic protein deposited outside of eosinophils in affected tissues, indicating that toxic granule proteins are released in diseased organs. Treatment included withdrawal of L-tryptophan in all cases. Corticosteroids were prescribed for 16 patients and diuretics alone for 1 patient; no drugs were prescribed for 3 patients. Four patients have recovered fully, others are stable or slowly recovering, and 1 is gravely ill despite prolonged treatment.