--monoclonal gammopathies are a known cause of neuropathy, whether they are of "undetermined significance" or associated with other blood disorders.

This is the thought to be the result of the antibodies cross-reacting with certain nerve structures. Quite often, there are also other autoantibodies to components to peripheral nerve present, such as antibodies to myelin associated glycoprotein (anti-MAG). These should be tested for.

See:

http://neuromuscular.wustl.edu/antibody/mprotein.htm

http://www.neuropathy.org/site/DocSe...pdf?docID=1061