Autoimmune inflammatory neuropathy

Inflammation of peripheral nerves may be due to autoimmune disease, infection or vasculitis. The nerve fibres are normally protected by a specialised endothelium, positive endoneurial pressure and perineurial barrier. Most cases of inflammatory neuropathy are characterised by endoneurial inflammation and primary demyelination without infection or vasculitis, and are thought to have an autoimmune pathogenesis. Macrophages penetrate the Schwann cell basement membrane, ingest the myelin sheath and denude the axon (Fig 1(a)–(c)). If the inflammation is severe, the axons may undergo ‘bystander’ degeneration. In rare cases, the autoimmune response is directed against the axon and causes a primary axonal neuropathy (Fig 2). Some organisms, such as Mycobacterium leprae and herpes zoster, have a special ability to grow within Schwann cells or sensory neurons. Vasculitis, particularly Churg-Strauss syndrome and polyarteritis nodosa, may affect peripheral nerves, usually causing acute axonal degeneration, very occasiona lly demyelination, and producing the clinical picture of multiple mononeuropathy or symmetrical polyneuropathy. Rarely, vasculitis is confined to peripheral nerves. This review focuses on autoimmune inflammatory neuropathy. There is a temporal spectrum of inflammatory demyelinating polyradiculoneuropathies with similar pathology, from acute through subacute to chronic (Table 1), although there is an unexplained difference in response to steroid treatment. Guillain-Barré syndrome (GBS), the commonest clinical presentation of an autoimmune neuropathy, is now agreed to be a heterogeneous condition incorporating several pathological entities2.