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Vasculitis is an immune-mediated disorder directed against blood vessels, which results in ischemia to end organs supplied by the affected blood vessels.15 The vasculitides can be distinguished and classified based on at least three nosologic categories. They can be differentiated based on the caliber of vessel involved (i.e., small, medium, or large vessel). They can be distinguished on whether the disorder is primary [e.g., polyarteritis nodosa (PAN), microscopic polyangiitis (MPA), granulomatosis with polyangiitis (GAN, formerly known as Wegener granulomatosis), and Churg–Strauss syndrome (CSS)] or secondary to other systemic disorders (e.g., connective tissue disease, malignancy, infection, or drug reaction). Furthermore, the vasculitides can be separated based on whether they are systemic or isolated to the peripheral nervous system (PNS), and if associated with antineutrophil cytoplasmic antibodies (ANCAs) (Table 15-1).2,3 Vasculitis is much more common in adults but can develop in children.6



PNS vasculitis can present as (1) a mononeuropathy or multiple mononeuropathies, (2) overlapping mononeuropathies, or (3) distal symmetric polyneuropathies (Fig. 15-1).38 In the first pattern, patients may present with just a mononeuropathy, but usually multiple nerves eventually become affected over time, giving a distinct asymmetric pattern of involvement in the distribution of individual nerves. With the second pattern, different nerves on both sides of the body are affected but to varying degrees, leading to a generalized, yet asymmetric, pattern of involvement. Finally, with gradual progression, somewhat uniform and generalized involvement of peripheral nerves results in what looks like a distal symmetric polyneuropathy. Approximately 60–70% of patients present with mononeuropathy or multiple mononeuropathies (multifocal neuropathy or mononeuropathy multiplex pattern), while 30–40% of patients present as a distal symmetric polyneuropathy.7 There is a large differential diagnosis of patients with a multiple mononeuropathy (Table 15-2). For this reason, multifocal neuropathy, multiple mononeuropathies, or mononeuropathy multiplex are preferable terminologies to mononeuritis multiplex because the latter term implies a histologically defined disorder rather than a clinically defined syndrome.

Figure 15-1.

Patterns of involvement in vasculitic neuropathy. Vasculitis can present as (A) a mononeuropathy or multiple mononeuropathies, (B) overlapping mononeuropathies, or (C) distal symmetric polyneuropathies.


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