Pellagra probably due to pyrazinamide: development during combined chemotherapy of tuberculosis.

Pellagra secondary to antituberculous chemotherapy can result from isoniazide therapy, as well as from pyrazinamide treatment. Because of the similarity in structural formulas between pyrazinamide, isoniazide, and nicotinamide, the substrate competition is the mechanism most likely involved. The patient was cured by administration of nicotinamide during continued unchanged chemotherapy of her tuberculosis.