Significance of immunoglobulin deposition in peripheral nerve in neuropathies associated with paraproteinaemia.

Direct and indirect immunofluorescent studies of sural nerves were carried out in two patients with paraproteinaemia and neuropathy, in four other patients with axonal or demyelinating neuropathies, and in one normal sural nerve. IgM was demonstrated directly in the two cases of paraproteinaemia and neuropathy, and indirectly, using the serum of one of these cases, in a case of axonal neuropathy and in one case of chronic Guillain-Barré syndrome. In the latter case, IgM deposition also occurred after exposure to normal serum. These results suggest that the paraprotein itself did not directly cause neuropathy, but that immunoglobulin deposition is probably a secondary process, caused by diffusion into damaged nerves.