From the Guidelines
Microscopic polyangiitis (MPA) is a rare autoimmune disorder characterized by inflammation of small blood vessels throughout the body, primarily affecting the kidneys and lungs, and is caused by anti-neutrophil cytoplasmic antibodies (ANCA), particularly those targeting myeloperoxidase (MPO-ANCA).
Definition and Cause
The disorder is part of a group of conditions known as ANCA-associated vasculitides (AAV) and is distinct due to its lack of granulomatosis and eosinophilia compared to other forms like granulomatosis with polyangiitis (GPA) and eosinophilic granulomatosis with polyangiitis (EGPA) 1.
Treatment Approach
Treatment typically involves a two-phase approach: induction therapy to achieve remission, followed by maintenance therapy to prevent relapse.
- Induction therapy may include a combination of high-dose corticosteroids and either cyclophosphamide or rituximab, with the choice depending on the severity of the disease and patient-specific factors 1.
- Maintenance therapy often involves less toxic medications such as azathioprine, methotrexate, or mycophenolate mofetil, continued for at least 18-24 months after achieving remission 1.
Specific Considerations
- Plasma exchange may be considered for severe disease with pulmonary hemorrhage or rapidly progressive glomerulonephritis, as it has been shown to improve outcomes in these scenarios 1.
- Regular monitoring of kidney function, complete blood counts, and inflammatory markers is essential for managing the disease and adjusting treatment as necessary.
- The treatment approach should be individualized, taking into account the patient's clinical condition, values, and preferences, and should be managed in close collaboration with, or at, centers of expertise due to the complexity and variability of the disease 1.
From the Research
Definition and Characteristics of Microscopic Polyangiitis (MPA)
- Microscopic polyangiitis (MPA) is a member of the family of ANCA-associated vasculitides 2
- It is characterized by a necrotizing small vessel vasculitis with little or absent immune deposits (pauci-immune vasculitis) 2
- MPA affects small and medium-sized vessels and is associated with a focal and segmental necrotizing glomerulonephritis 3
Organ Involvement
- The two organs most typically involved and often defining prognosis are the kidneys and the lungs 2
- MPA may concomitantly or sequentially involve other organs such as the nervous system, the skin, the musculoskeletal system, but also the heart, the eye, and the intestines 2
- Pulmonary involvement can range from antecedent interstitial fibrosis to frank hemoptysis secondary to capillaritis 4
- Central and peripheral nervous system involvement is extremely rare, but can occur 5
Diagnosis and Treatment
- Antineutrophil cytoplasmic antibodies (ANCA) are important in diagnosis as well as in the pathogenesis and prognosis of MPA 4, 3
- Treatment decisions should be based on severity and pattern of organ involvement and respect the five factor score (FFS) 2
- Life- or organ-threatening disease is treated with glucocorticoids and (pulse) cyclophosphamide, with plasmapheresis and i.v. immunoglobulins as additional measures in severe cases 2
- Maintenance therapy is recommended with Azathioprin, and mycophenolate mofetil may be used as a second-line drug 2
- Biologic agents such as monoclonal antibodies to tumor necrosis factor alpha and B cell-depleting rituximab have been shown to have remission-inducing quality 2, 5