Distinctive clinical features in biopsy-proven nerve large-arteriole vasculitis and microvasculitis

Vasculitic neuropathy is caused by inflammatory destruction of nerve blood vessels resulting in nerve ischemia. Nerve vasculitis can be divided into two categories based on vessel size - large arteriole vasculitis (≥75 µm) and microvasculitis (<75 µm). Herein, we characterize the clinical features of nerve large-arteriole vasculitis compared to nerve microvasculitis. This is a retrospective cohort study of patients evaluated and biopsied at Mayo sites between 2001 to 2020. We collected clinical and histopathological data from patients whose nerve biopsies were either diagnostic or highly suggestive of nerve vasculitis. 278 cases were identified; 125 cases of large-arteriole vasculitis and 153 cases of microvasculitis. Nerve large-arteriole vasculitis presented with a more acute (50.4% vs 26.8%) vs. chronic onset (33.6% vs 57.5%) than nerve microvasculitis (p= 0.0001). Nerve microvasculitis had longer mean time to diagnosis (10.5 vs 4.3 months; p < 0.0001), and longer time to plateau (8.9 vs 3.5 months; p <0.0001). Nerve large-arteriole vasculitis typically presented as distal asymmetric polyneuropathy (48.0%) whereas nerve microvasculitis typically presented as radiculoplexus neuropathy/polyradiculoneuropathy (more proximal involvement of shoulder and thigh) (43.8%) (p < 0.0001). Systemic autoimmune disease was more common in nerve large-arteriole vasculitis (70.4% vs 22.9%, odds ratio, 8.0; 95% confidence interval [CI], 4.7-13.7; p < 0.0001). Nerve microvasculitis was significantly related to non-systemic vasculitis (71% vs 23%, odds ratio, 7.9; (95%CI), 4.6-13.6; p<0.0001). Nerve microvasculitis had more autonomic involvement (24.2% vs 7.2%, odds ratio, 4.1; (95% CI), 1.9-8.9; p = 0.0002). Nerve large-arteriole vasculitis and nerve microvasculitis have different but overlapping clinical features. Nerve large-arteriole vasculitis usually presents with acute onset, distal asymmetric polyneuropathy, associated with other autoimmune diseases and systemic involvement. In contrast, nerve microvasculitis presents usually with a subacute/chronic onset, as radiculoplexus neuropathy/polyradiculopathy (distal and proximal pattern) with autonomic involvement and is more often a form of non-systemic vasculitis.