Long-term survival, causes of death, and prognostic factors for mortality in patients with microscopic polyangiitis and those with anti-neutrophil cytoplasmic antibody-positive interstitial lung disease: A single-center retrospective study.

Aim: To elucidate the clinical features, long-term survival, and prognostic factors for mortality among patients with microscopic polyangiitis (MPA), including those with anti-neutrophil cytoplasmic antibody-positive interstitial lung disease (ILD) (ANCA-ILD), which could be a subset of its variant phenotype.

Methods: We retrospectively included 76 consecutive patients between 2006 and 2014, diagnosed with MPA according to the European Medicines Agency algorithm using the Chapel Hill Consensus Conference definitions or ANCA-ILD. ILD was classified as usual interstitial pneumonia (UIP) or nonspecific interstitial pneumonia pattern using chest computed tomography.

Results: The mean (standard deviation) age of the patients (female, 68%) was 69 (12) years. The median (interquartile range) follow-up period was 68 (33-95) months. Comorbid ILD and glomerulonephritis were observed in 44 (58%) (68% UIP) and 54 (71%) patients, respectively. Comorbid ILD was associated with low survival (P = .0563). There were 17 (39%) and 5 (16%) deaths in the ILD and non-ILD groups, respectively (P = .0404). In the ILD group, 6 and 5 of the deaths were attributed to infection and ILD progression, respectively. In the non-ILD group, 1 and 2 patients expired from subsequently developed ILD and aspiration pneumonia, respectively. Age ≥ 70 years (hazard ratio = 2.78; 95% confidential interval 1.15-6.70) and UIP (3.95; 1.60-9.77) were independent risk factors for mortality.

Conclusion: Age ≥ 70 years and ILD with a UIP pattern were associated with high mortality, owing to susceptibility to infection and ILD progression. A more effective and less toxic treatment is required for progressive ILD.