How would you approach a patient with MPO-positive isolated peripheral nerve vasculitis?

AAV can present with a peripheral neuropathy as a first manifestation. The first question we're often facing is whether a biopsy is necessary. If the neuropathy pattern is one of mononeuritis multiplex and there are no atypical features or other atypical serologic findings, I sometimes forego nerve biopsy since mononeuritis is a much more specific pattern for vasculitic neuropathy, however, many experts will choose to do a nerve biopsy when neuropathy is the only feature. However, keep in mind t...

Vasculitic neuropathy is often extremely painful and debilitating, and management can be challenging. In this case, the first step is to make sure the underlying diagnosis is in fact small vessel vasculitis by obtaining nerve biopsy and then determining if the patient has a non-systemic vasculitic neuropathy (NSVN) vs a primary or secondary systemic vasculitis with nerve involvement.

If the MPO ANCA is elevated and the biopsy is consistent with vasculitis, I would pursue immunosuppression and phy...