title: [Microscopic polyangiitis].
abstract: Microscopic polyangiitis was initially considered a "microscopic" form of polyarteritis nodosa and was not definitively distinguished from it until the Chapel Hill nomenclature (1994). Microscopic polyangiitis is a systemic necrotizing vasculitis of small vessels. Its typical clinical manifestations are rapidly progressive glomerulonephritis and alveolar hemorrhage. Other possible symptoms resemble those encountered in polyarteritis nodosa. Microscopic polyangiitis belongs to the group of ANCA-associated vasculitides, and 75-80% of patients have pANCA to myeloperoxidase (MPO). Anti-MPO ANCA pathogenicity has been established in animal models, and a recent report describes transplacental transfer of these antibodies in humans, resulting in pulmonary hemorrhage and renal involvement in the newborn. Patients with no poor prognostic factors, as defined by a five-factor score, can be treated with corticosteroids alone, with immunosuppressants added only in case of treatment failure. Patients with one or more poor prognostic factors must receive a combination of corticosteroids and immunosuppressants, mainly intravenous pulsed cyclophosphamide, with plasma exchange as an adjuvant therapy for those with severe renal involvement. Once remission is achieved, maintenance therapy can replace cyclophosphamide by azathioprine or methotrexate. Biological therapies are under evaluation. The remission rate is above 80% with these regimens, and the relapse rate is around 30% at 5 years, lower than for Wegener's granulomatosis.
authors.affiliation: Service de médecine interne, Centre de référence national, Plan Maladies rares, vascularites nécrosantes et sclérodermie systémique, Hôpital Cochin, AP-HP, Université Paris 5 - René Descartes, Paris, France.
authors.forename: Christian
authors.initials: C
authors.lastname: Pagnoux
authors.forename: Philippe
authors.initials: P
authors.lastname: Guilpain
authors.forename: Loïc
authors.initials: L
authors.lastname: Guillevin
mesh_terms: D000305:Adrenal Cortex Hormones / Q000627:therapeutic use; D000367:Age Factors; D019268:Antibodies, Antineutrophil Cytoplasmic; D001379:Azathioprine / Q000008:administration & dosage / Q000627:therapeutic use; D001691:Biological Therapy; D002986:Clinical Trials as Topic; D003520:Cyclophosphamide / Q000008:administration & dosage / Q000627:therapeutic use; D003937:Diagnosis, Differential; D004359:Drug Therapy, Combination; D005260:Female; D005500:Follow-Up Studies; D005921:Glomerulonephritis / Q000209:etiology; D006801:Humans; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D007231:Infant, Newborn; D008171:Lung Diseases / Q000209:etiology; D008297:Male; D008727:Methotrexate / Q000008:administration & dosage / Q000627:therapeutic use; D008875:Middle Aged; D010951:Plasma Exchange; D010488:Polyarteritis Nodosa / Q000175:diagnosis; D011379:Prognosis; D012008:Recurrence; D012074:Remission Induction; D012871:Skin Diseases / Q000209:etiology; D013997:Time Factors; D014657:Vasculitis / Q000150:complications / Q000175:diagnosis / Q000188:drug therapy / Q000453:epidemiology / Q000209:etiology / Q000276:immunology / Q000401:mortality
chemical_list: D000305:Adrenal Cortex Hormones; D019268:Antibodies, Antineutrophil Cytoplasmic; D007166:Immunosuppressive Agents; D003520:Cyclophosphamide; D001379:Azathioprine; D008727:Methotrexate