Wegener's granulomatosis is a systemic vasculitis characterized by necrotizing granulomata and without treatment is associated with a poor prognosis. Antineutrophil cytoplasmic antibodies (ANCA) have proved to be a useful serological marker allowing for early diagnosis and treatment of this condition. We report two cases of patients who were ANCA-negative on presentation despite clinical suspicion of Wegener's granulomatosis. In both cases the patients developed a positive ANCA titre as the disease progressed.
