Incidence and risk factors of new-onset hypertrophic pachymeningitis in patients with anti-neutrophil antibody-associated vasculitis: using logistic regression and classification tree analysis

Abstract

Objectives: Hypertrophic pachymeningitis (HP) is a rare complication in patients with anti-neutrophil antibody-associated vasculitis (AAV); its clinical features, incidence, and risk factors remain unknown. We aimed to clarify the prevalence, clinical features, and factors associated with new-onset HP in patients with AAV. Method: A retrospective cohort study involving 93 patients with AAV was conducted. HP incidence between patients with granulomatosis with polyangiitis (GPA) and those with microscopic polyangiitis (MPA) was compared to investigate risk factors associated with HP. We performed only univariate analysis using logistic regression and classification tree (CART) analysis due to the small number of HP cases. Results: Among the 93 patients (76 with MPA and 17 with GPA), only 6 patients developed HP (1 with MPA, 5 with GPA) over an average observation period of 4 years; all patients who developed HP were positive for myeloperoxidase anti-neutrophil antibody. HP incidence was significantly higher in patients with GPA than in those with MPA (60.2 versus 3.3 persons per 1000 person-years, respectively, P = 0.002). The univariate analysis revealed that otitis media (P < 0.001) and sinusitis (P = 0.014) were associated with new-onset HP. Univariate CART analysis grouped the patients into patients with HP who have otitis media (33%) and patients with HP who have sinusitis (21%). The odds ratio of otitis media adjusted by age and first diagnosis of AAV was 38.1 (95% confidence interval, 3.08–331.4; P = 0.004). Conclusions: Although only in the univariate analysis, otitis media was the most discriminating factor to predict new-onset HP in patients with AAV.