Microscopic Polyangiitis: New Insights into Pathogenesis, Clinical Features and Therapy

Area of Science:

• Nephrology
• Rheumatology
• Immunology

Background:

• Microscopic polyangiitis (MPA) is a key clinical form of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitides.
• Anti-myeloperoxidase (MPO) antibodies are present in nearly 80% of MPA patients, with proven pathogenicity in animal models.
• MPA commonly impacts the kidneys and lungs, presenting as glomerulonephritis or diffuse alveolar hemorrhage.

Purpose of the Study:

• To summarize the clinical presentation, organ involvement, and outcomes of microscopic polyangiitis.
• To highlight the role of anti-MPO antibodies in MPA pathogenesis.
• To underscore the mortality risks and the need for optimized immunosuppressive strategies.

Main Methods:

• Review of clinical and pathological criteria for MPA diagnosis.
• Analysis of the prevalence and pathogenic role of anti-MPO antibodies.
• Examination of organ-specific manifestations (renal and pulmonary).
• Assessment of disease prognosis, mortality rates, and causes of death.

Main Results:

• Anti-MPO antibodies are highly prevalent in MPA and play a pathogenic role.
• Kidney involvement includes rapidly progressive or slowly progressive glomerulonephritis, potentially leading to end-stage renal disease.
• Pulmonary manifestations range from diffuse alveolar hemorrhage to chronic interstitial fibrosis.
• General symptoms like fever, weight loss, neuropathy, and skin issues can also occur.
• Five-year mortality is 25%, increased in elderly patients or those with renal impairment, with infections being a major cause of death.

Conclusions:

• MPA is a serious condition with significant morbidity and mortality, particularly affecting the kidneys and lungs.
• Anti-MPO antibodies are central to the disease's pathogenesis.
• Optimizing maintenance immunosuppression is crucial to reduce treatment-related mortality, especially from infections.