[Polyneuropathies and monoclonal gammopathies, so-called benign].

As all other monoclonal dysglobulinaemias, the allegedly benign monoclonal dysglobulinaemia (also called of undetermined nature) can be responsible for peripheral neuropathy. It must be noted that electrophoresis and immuno-electrophoresis may be insufficient to demonstrate its presence and that this can be done with specific immunological techniques, such as ELISA or immunoblot). Once the monoclonal gammopathy has been recognized, its relation to the peripheral nerve lesion is not always easy to prove. Antibody activity against certain constituents of the nerve can sometimes be evidenced, notably for IgM. It is interesting to point out that almost all IgM-related neuropathies have highly characteristic clinical, histological and immunological features. Various other mechanisms, often still unknown, are most probably involved.