Association Between Idiopathic Cutaneous Leukocytoclastic Angiitis and ANCA-negative Microscopic Polyangiitis

Objective. This study retrospectively reviewed the process of classifying antineutrophil cytoplasmic antibody (ANCA)-negative granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA) in a cohort of patients with ANCA-associated vasculitis (AAV), and investigated the association between recurrent idiopathic cutaneous leukocytoclastic angiitis and ANCA-negative MPA. Methods. The medical records of 242 patients with AAV were retrospectively reviewed. Of 49 patients with ANCA-negative AAV, 24 patients with ANCA-negative eosinophilic GPA (EGPA) were excluded, because ANCA positivity or negativity is not critical in classifying EGPA. Ultimately, 25 patients with ANCA-negative GPA and MPA were analysed in this study. The classification of GPA and MPA were based on the 2007 European Medicines Agency algorithm for AAV. Results. The median age of patients with ANCA-negative GPA and MPA was 54.0 years and 24% were male. Of the 25 patients without ANCA, 8 patients were classified as GPA and 17 as MPA. Eight patients with ANCA-negative GPA were easily confirmed as definitive GPA. Fourteen of the 17 patients ANCA-negative MPA were classified as MPA based on histological features suggestive of AAV without granuloma formation and the absence of surrogate markers for GPA. Meanwhile, three of the patients that were ANCA-negative exhibited only recurrent idiopathic cutaneous leukocytoclastic angiitis without other major organs affected and thus were classified as possible MPA. Within one year, they were classified as definitive MPA based on ANCA positivity and/or renal histology. Conclusion. Recurrent idiopathic cutaneous leukocytoclastic angiitis may be associated with ANCA-negative MPA in patients who exhibit cutaneous necrotising vasculitis.