Anti-neutrophil cytoplasmic antibody (
ANCA)-associated vasculitis is a systemic disorder that frequently affects the peripheral nervous system and consists of three distinct conditions:
microscopic polyangiitis (MPA),
granulomatosis with polyangiitis (GPA, previously
Wegener's granulomatosis), and
eosinophilic granulomatosis with polyangiitis (EGPA, previously
Churg-Strauss syndrome). The neuropathic features associated with this condition usually include
mononeuritis multiplex, which reflects the locality of lesions. Findings suggestive of
vasculitis are usually found in the epineurium and occur diffusely throughout the nerve trunk. Nerve fiber degeneration resulting from
ischemia is sometimes focal or asymmetric and tends to become conspicuous at the middle portion of the nerve trunk. The attachment of neutrophils to endothelial cells in the epineurial vessels is frequently observed in patients with
ANCA-associated vasculitis; neutrophils play an important role in vascular
inflammation by binding of
ANCA. The positivity rate of
ANCA in EGPA is lower than that in MPA and GPA, and intravascular and tissue eosinophils appear to participate in neuropathy.
Immunotherapy for
ANCA-associated vasculitis involves the induction and maintenance of remission to prevent the relapse of the disease. A combination of
glucocorticoids along with
cyclophosphamide,
rituximab,
methotrexate, or
mycophenolate mofetil is considered depending on the severity of the condition of the organ to induce remission. A combination of low-dose
glucocorticoids and
azathioprine,
rituximab,
methotrexate, or
mycophenolate mofetil is recommended to maintain remission. The efficacy of anti-interleukin-5
therapy (i.e.,
mepolizumab) was demonstrated in the case of refractory or relapsing EGPA. Several other new agents, including
avacopan,
vilobelimab, and
abatacept, are under development for the treatment of
ANCA-associated vasculitis. Multidisciplinary approaches are required for the diagnosis and management of the disorder because of its systemic nature. Furthermore, active participation of neurologists is required because the associated neuropathic symptoms can significantly disrupt the day-to-day functioning and quality of life of patients with
ANCA-associated vasculitis.