Anti-myelin-associated glycoprotein antibodies and endoneurial cryoglobulin deposits responsible for a severe neuropathy.
Acta Neuropathol. 2001-10-01; 102(4): 409-412
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A 73-year-old man was investigated for a peripheral neuropathy which occurred in
the course of a Waldenstrom’s macroglobulinemia. Serum immuno-fixation
electrophoresis demonstrated two IgM monoclonal gammopathies of the kappa and
lambda chain isotypes, and one had the physical characteristics of cryoglobulin.
Immunoblot studies on the patient’s serum revealed antibodies which reacted with
peripheral nervous system proteins of different molecular weights including the
myelin-associated glycoprotein (MAG). An immunofluorescence study of a
superficial peroneal nerve biopsy revealed not only a binding of IgM and kappa
light chain on several myelin sheaths but also the presence of IgM and kappa
light chain deposits in the endoneurium. On electron microscopic examination,
numerous fibres presented a widely spaced myelin and the endoneurial deposits had
the ultrastructure of cryoglobulin. This is the first case presenting features of
widely spaced myelin related to serum anti-MAG activity associated with
monoclonal cryoglobulin deposits in the endoneurium.