The antineutrophil cytoplasmic antibody (ANCA) associated vasculitides (AAV) are a group of primary vasculitides that affect predominantly small- to medium-sized blood vessels. The pathology of granulomatosis with polyangiitis (GPA) typically features a granulomatous and sometimes necrotizing vasculitis targeting predominantly the respiratory tract and kidneys, including necrotizing granulomatous inflammation. The diagnosis can be delayed due to the nonspecific nature of the symptoms. Cyclophosphamide and glucocorticoids have been the cornerstone of remission-induction therapy for severe antineutrophil cytoplasmic antibody-associated vasculitis for years. Recently, the monoclonal antibody rituximab was approved for the treatment of GPA, providing an alternative to cyclophosphamide for induction therapy of AAV. In the present case study we used azathioprine as the maintenance drug. However, because of relapse we tried mycophenolate mofetil (MMF) as a second-line drug successfully. This case confirms that MMF is not only well tolerated but also effective in GPA to maintain remission.