Peripheral neuropathy in systemic vasculitides

Abstract

Peripheral nervous system (PNS) involvement is of great diagnostic value in systemic vasculitides, because it occurs frequently and often early during the course of these diseases, despite the supposed blood-nerve barrier that should prevent or at least minimize PNS damage. However, it carries no poor prognostic value in vasculitides. Recent advances have been made in understanding the pathogenetic mechanisms of PNS involvement. Vasculitic neuropathy may result from primary or secondary systemic vasculitides, or may be restricted to the PNS, in a form that is now also considered to be a systemic vasculitis. The blood-nerve barrier is not as efficient as the blood-brain barrier. Inflammatory cell infiltration into the vasa nervorum and epineurial arteries leads to ischemic axonal nerve injury and is facilitated by additional breaches in the blood-nerve barrier, induced by proinflammatory cytokines, oxidative stress-derived molecules, and matrix metalloproteinases. Although animal models of myeloperoxidase or, now, proteinase 3-antineutrophil cytoplasmic autoantibody-inducing vasculitis have been developed, they do not support a role for antineutrophil cytoplasmic autoantibodies in PNS involvement. Treatment should be chosen based on the other organ involvement and the patient's general condition. When PNS involvement is isolated, corticosteroids alone should be used as first-line treatment. Apart from the so-called nonsystemic nerve vasculitis, PNS involvement is rarely the sole clinical sign of systemic necrotizing vasculitis, and its association with other typical manifestations is often suggestive of the diagnosis of vasculitis. Herein are summarized recent advances that have clarified but not yet fully elucidated the pathogenesis of peripheral neuropathy in systemic vasculitides, together with the latest clinical findings and therapeutic strategies.