Maintaining remission in patients with granulomatosis with polyangiitis or microscopic polyangiitis: the role of ANCA

Introduction: Granulomatosis with Polyangiitis (GPA; formerly Wegener's) and Microscopic Polyangiitis (MPA) are inflammatory disease entities affecting small to medium vessels. They are characterized by the presence of anti-neutrophil cytoplasmic antibodies (ANCA) and are frequently grouped together with Eosinophilic Granulomatosis with Polyangiitis (EGPA; formerly Churg Strauss Syndrome) under the term ANCA-associated Vasculitis (AAV). Due to effective immunosuppressive therapy that was introduced more than 45 years ago, AAV has become a chronic disease in which relapses occur frequently during maintenance treatment or later on after all immunosuppressive therapy is stopped. Since relapses are associated with morbidity and mortality, early detection and prevention of relapses is of great importance. Areas covered: This review focuses on the potential strategies to guide maintenance therapy in patients with GPA or MPA, with an emphasis on patient classifications and the role of serial ANCA measurements. Expert opinion: Risk factors for relapses, e.g., genetic background of the patient, have been studied during the last three decades. Only few of these risk factors directly influence the management of patients. One potentially important factor that may influence therapeutic decisions in AAV patients is serial measurement of ANCA. Recently, it became clear that serial ANCA measurement is an attractive approach in AAV patients with (a history of) capillaritis, e.g., renal involvement or alveolar haemorrhage, but not in patients with more limited disease. Whether ANCA rises can be used to guide therapy and - hence- to prevent relapses has been a great debate during the last three decades. At present, we conclude that small studies do support such an approach but that these findings require further validation in larger randomized clinical trials