Abstract
Five tryptophan metabolites were measured in the urine after an oral tryptophan load in patients with rheumatoid arthritis, scleroderma, systemic lupus and a variety of other diseases. An excessive excretion of kynurenine and 3‐hydroxykynurenine was a common but nonspecific occurrence in rheumatic disease. The excretion did not correlate well with various clinical parameters. Inhibition of pyridoxal‐dependent hepatic enzymes may be the cause of the abnormality but the mechanism is unknown.