Diagnosis:
- This is a category of different neuropathies.
- Neuropathy due to a gammopathy includes anti-MAG syndrome, POEMS, cryoglobulinemia, IgM MGUS polyneuropathy, Anti-GALOP (IgM against central myelin antigen): Gait Disorder, Autoantibody Late-age Onset Polyneuropathy
- Evidence of paraproteinemia e.g. SPEP: paraproteinemia
Pathology, nerve biopsy:
Light microscopy:
- Nonspecific, loss of myelin and/or axons
- No inflammation except in cryoglobulinemia
- For cryoglobulinemia: features of vasculitic neuropathy
Immunohistochemsitry:
- Immunofluorescence with Anti-immunoglobulin for anti-MAG syndrome
Electron microscopy EM:
- Widened myelin lamellae IgM
- Uncompacted myelin lamellae (POEMS)
- Capillary deposits (cryoglobulinemia)
Treatment:
Options:
- Plasma exchange
- Prednisone
- Intravenous immunoglobulin IVIG
- Azathioprine
- Cyclophosphamide
For IgM MGUS polyneuropathy:
- Cyclophosphamide 500 mg P.O. once DAILY X4 days +prednisone 60 mg P.O. once DAILY X5 days, every 28 days for 6 treatments.