Longterm Outcomes of 188 Japanese Patients with Eosinophilic Granulomatosis with Polyangiitis.

Objective: Patients with eosinophilic granulomatosis with polyangiitis (EGPA) frequently experience relapses, which lead to cumulative organ damage. In this retrospective observational study, we aimed to reveal the risk factors for relapse in EGPA.

Methods: A total of 188 Japanese patients with EGPA diagnosed between 1996 and 2015 were identified from medical records in 10 hospitals. The diagnosis was based on the American College of Rheumatology 1990 criteria or Lanham's criteria. Baseline characteristics, treatments, asthma exacerbation, and relapses were evaluated by retrospective chart review.

Results: The median followup period was 56 months. The median age at disease onset was 59.7 years. At the disease onset, 95.2% of the patients had a history of bronchial asthma and 44.7% were positive for antineutrophil cytoplasmic antibodies. The cumulative survival and relapse-free survival rates at 5 years were 89.6% and 64.0%, respectively. Multivariate analysis with 2 models, proportional hazards, and competing risk models, was performed to identify the factors associated with relapse. The proportional hazards model identified azathioprine (AZA) maintenance therapy and high eosinophil counts at onset as independent factors with lower relapse risks, and high immunoglobulin E (IgE) levels at onset as a risk factor for relapse. The competing risk model identified no statistically significant factors.

Conclusion: Although potential benefit of AZA maintenance therapy in preventing relapse of EGPA was suggested by the proportional hazards model, there was a discrepancy in the results between the models. Eosinophil counts and IgE levels at onset were also identified as candidates of factors associated with relapse in EGPA.