Background/Purpose: Microscopic polyangiitis (MPA) is a systemic ANCA-associated small-vessel necrotizing vasculitis characterized by general symptoms, and visceral manifestations, including rapidly progressive glomerulonephritis and alveolar hemorrhage. The main characteristics and long-term outcomes of a nationwide patient cohort are described.

Methods: French Vasculitis Study Group’s cohort patients with MPA, satisfying Chapel Hill criteria, were studied retrospectively. Their characteristics at diagnosis, 2009 Five Factor Score (FFS) and Birmingham Vasculitis Activity Score (BVAS) were collected. For the earliest recruits, ANCA tests were not available. MPA diagnoses were reassessed, taking follow-up into account. Patients’ overall (OS) and relapse-free survival (RFS) were analyzed using log-rank tests and multivariable Cox proportional hazards models.

Results: Patients (n=382) were diagnosed between 1966 and 2017 (30 [8%] before 1990, 101 [26%] 1990–2000, 152 [40%] 2000–2010 and 99 [26%] after 2010), and followed-up for (mean ± SD) 5.5 ± 4.6 yr. At diagnosis, mean ± SD age was 61.1 ± 15.1 yr, with 182 (48%) >65 yr old. Main clinical manifestations included fever >38°C (45%); weight loss (57%); arthralgias (45%); myalgias (40%); purpura (19%); mononeuritis multiplex (33%). Creatinine levels rose >30% in 154 (40%) patients, with mean ± SD creatininemia at 215 ± 223 µmol/L, and creatininemia >150 µmol/L for 158 (41%) patients. Alveolar hemorrhage occurred in 59 (16%; with massive hemorrhage and/or hemoglobin <9 g/dL in 17 (4.5%)) patients, cardiomyopathy in 22 (6%) and severe gastrointestinal signs (bleeding, perforation, pancreatitis) in 15 (4%). IF ANCA test results were available for 350 patients and ELISA for 345; 276 (80%) patients were anti-MPO–ANCA+ and 13 (3.7%) anti-PR3+. FFSs were 0 for 110 (29%) patients, 1 for 181 (47%), ≥2 for 91 (24%). Median BVAS was 17.3. Glucocorticoids alone were induction for 92 patients (24%); 280 also took an immunosuppressant, including rituximab for 43 (11%). After a mean ± SD of 3.0 ± 2.9 yr, 133 (35%) patients had relapsed. Respective 5-year OS and RFS were 86.9% and 60.5%. Over the last 40 yr, OS increased from 63% before 1990 to 94% after 2010 (P for trend <0.001), but not RFS. FFS≥1 and an increased BVAS were associated with death (P<0.0001 and <0.0001, respectively). Multivariable analyses (hazard ratio; 95% confidence interval) retained age >65 yr (4.6; 2.7–7.8), the need for assisted ventilation (3.9; 1.3–11.5), creatininemia >150 µmol/L (2.6; 1.6–4.2) and mononeuritis multiplex (1.9; 1.1–3.2) as independent risk factors for death; and cardiomyopathy (1.8; 1.0–3.0), severe gastrointestinal manifestations (2.1; 1.1–3.8) and mononeuritis multiplex (1.7; 1.3–2.3) as factors associated with poor relapse-free survival. Immunosuppressant use for induction therapy did not modify those results.

Conclusion: This retrospective study provides useful information on the characteristics and outcomes of a large cohort of MPA patients. OS improved over decades. However, data collection before ANCA discovery and evolution of therapeutic strategies may represent a study limitation.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/clinical-characteristics-and-long-term-follow-up-of-382-microscopic-polyangiitis-patients/