Scleroderma and L-Tryptophan: A Possible Explanation of the Eosinophilia-Myalgia Syndrome

In 1990, a study reported that six women developed scleroderma-like conditions, including fasciitis and morphea, after taking L-tryptophan supplements. Symptoms improved when they stopped taking the supplement and started corticosteroid therapy. The study linked these cases to eosinophilia-myalgia syndrome (EMS), which had over 1000 reported cases associated with muscle pain and weakness that resolved after discontinuing L-tryptophan or with corticosteroids. Histopathologic findings suggested altered tryptophan metabolism could lead to connective tissue disease in some individuals. While not all individuals taking L-tryptophan develop EMS or scleroderma-like illnesses, a subset may be susceptible, and these conditions can improve with the cessation of L-tryptophan and possibly with corticosteroid treatment.