Drug-induced lupus erythematosus with in vivo lupus erythematosus cells in pleural fluid.

Pleural involvement in drug-induced lupus erythematosus is not uncommon. Lupus erythematosus cells were found in vivo in the pleural of an elderly patient who had received procainamide (Pronestyl) hydrochloride (2 gm daily) for nine months. Patients who initially have pleural effusions while receiving drugs capable of inducing lupus erythematosus should have the fluid analyzed for lupus erythematosus cells to help clarify the cause of the effusion.