Drug-induced lupus pleuritis mimicking pleural space infection

A 78-year-old man presented with acute lupus pleuritis due to procainamide. The pleural fluid was a turbid, yellow exudate with a WBC count of 53,200/cu mm (70 percent polymorphonuclear leucocytes), LDH of 4,296 IU/L, and pH of 7.195. Although these fluid characteristics suggested pleural space infection, they were due to pleural inflammation from drug-induced lupus. LE cells were present in the fluid and results of microbiologic studies were negative. Clinical and roentgenographic improvement followed discontinuation of procainamide.