False-positive antineutrophil cytoplasmic antibody in aspergillosis with oxalosis

Although highly specific for Wegener's granulomatosis and other vasculitides, false-positive antineutrophil cytoplasmic antibody is occasionally encountered in other nonvasculitic conditions. We report a case of clinically suspected Wegener's granulomatosis with a large pulmonary cavity, renal failure, and positive cytoplasmic antineutrophil cytoplasmic antibody reaction. The patient died before initiation of immunosuppressive therapy. Postmortem examination revealed pulmonary aspergillosis due to Aspergillus niger, with extensive pulmonary and renal oxalosis, which lead to renal failure. The possible role of oxalosis in the pathogenesis of false-positive antineutrophil cytoplasmic antibody reaction is discussed.