**1. Introduction**

Anti-neutrophil cytoplasmic antibodies-associated vasculitides (AAV) are rare autoimmune diseases of unknown etiology. They are characterized by cell inflammatory infiltration and necrosis of small vessels [1]. They are classified as microscopic polyangiitis (MPA) granulomatosis with polyangiitis (GPA, previously known as "Wegener's granulomatosis") and eosinophilic granulomatosis with polyangiitis (EGPA, formerly known as "Churg-Strauss syndrome") [2]. The systemic inflammation seen in these vasculitis result in organ- and life-threatening diseases with a polymorphous clinical presentation. AAV can affect the peripheral nervous system and that could be difficult to diagnose and treat. In cases of pre-existing systemic vasculitis, the diagnosis is easier to make, but when the vasculitis neuropathy is the initial or unique manifestation of the vasculitis, it requires careful clinical, neurophysiological, laboratory and sometimes histopathological investigation. The frequency of vasculitis-related neuropathy is variable and depends on the type of vasculitis [3]. In this chapter, we will discuss the pathogenesis, diagnosis, treatment and prognosis of neuropathies in AAV including the MPA, GPA and EGPA.
