Some 1 to 5 percent of patients with rheumatoid arthritis have vasculitic involvement of one or more nerves at some time in the course of their disease, apart from more mundane pressure neuropathies as a result of thickened tendons and destructive joint changes. The arteritis is of small-vessel fibrinoid type and immune globulins are demonstrable in the walls of vessels. Most of the affected patients under our care have had severe rheumatic disease for many years and were strongly seropositive (see Pallis and Scott). In addition to the neuropathy, such patients often have rheumatoid nodules, skin vasculitis, weight loss, and fever. There are rarer forms of chronic progressive polyneuropathy that complicate rheumatoid arthritis; they are described further on.
Approximately 10 percent of patients with lupus exhibit symptoms and signs of peripheral nerve involvement, but only a negligible number occur before the established and more advanced stages of the disease (i.e., rarely has it been the initial presentation). In our several patients, the polyneuropathy has taken the form of a symmetrical, progressive sensorimotor paralysis, beginning in the feet and legs and extending to the arms, evolving over a period of several days or weeks, thereby simulating GBS. In a few, weakness and areflexia were more prominent than the sensory loss; the latter involved mainly vibratory and position senses. A more common syndrome in our experience has been a progressive or relapsing disease that cannot be distinguished clinically from chronic inflammatory demyelinating polyneuropathy (discussed further on). Multiple mononeuropathies have also been reported, as has involvement of the autonomic nervous system. An elevation of CSF protein that is found in some instances suggests nerve root involvement. Sural nerve biopsies may show vascular changes consisting of endothelial thickening and mononuclear inflammatory infiltrates in and around the small vessels for which reason the disease is included here with the other vasculitic neuropathies. Axonal degeneration is the most common change, but a chronic demyelinating pathology has also been described (Rechthand et al). Vascular injury from deposition of immune complexes is the proposed mechanism of nerve damage.
In contrast to the aforementioned disorders, which involve several tissues and organs in addition to the peripheral nerves, necrotizing vasculitis may be limited to the peripheral nerves. Cases of this type appear as often as all the other systemic vasculitic types together. This restricted form of mononeuritis multiplex usually presents as a subacute symmetrical or asymmetrical polyneuropathy with superimposed mononeuropathies or solely with multiple mononeuritis. Circulating antineutrophil cytoplasmic antibody (ANCA) is found in a few cases, but other tests for inflammatory and connective tissue diseases are negative. In the series reported by Collins and colleagues (2003), the sedimentation rate was mildly elevated, the mean being 38 mm/h, with only one-quarter having values greater than 50 mm/h. The main diagnostic difficulty in diagnosis arises when the EMG performed early in the course of illness shows conduction block that simulates a demyelinating polyneuropathy. Nerve biopsy should then settle the issue.
Treatment The neuropathy tends to be less aggressive (and nonlethal) than the systemic forms of vasculitic neuropathy and has usually responded to corticosteroids without treatment with cyclophosphamide. However, in the aforementioned series reported by Collins, the use of cyclophosphamide for 6 months with corticosteroids resulted in a more rapid remission and fewer relapses. An expert group has provided guidelines for treatment specifically of this condition that approximates this approach by adding an immunosuppressive agent to corticosteroids only if the disease behaves aggressively (Collins et al, 2010).