Proposal for Criteria for Demyelinating Polyneuropathy Associated With Monoclonal Gammopathy of Undetermined Significance

A causal relation between chronic inflammatory demyelinating polyneuropathy and monoclonal gammopathy of undetermined significance should be considered in patients with:

1. Demyelinating polyneuropathy according to the electrodiagnostic American Academy of Neurology criteria for idiopathic chronic inflammatory demyelinating polyneuropathy.

2. Presence of an M protein (immunoglobulin [Ig]M, IgG, or IgA), without evidence of malignant plasma cell dyscrasias, such as multiple myeloma, lymphoma, Waldenstrom's macroglobulinemia, or amyloidosis.

3. Family history negative for neuropathy.

4. Age over 30 years.

The relation is definite when the following is present:

1. IgM M protein with antimyelin-associated glycoprotein (MAG) antibodies. The relation is probable when at least three of the following are present in a patient without anti-MAG antibodies:

1. Time to peak of the neuropathy greater than 2 years.

2. Chronic, slowly progressive course without relapsing or remitting periods.

3. Symmetric distal polyneuropathy.

4. Sensory symptoms and signs predominate over motor features.

A causal relation is unlikely when at least three of the following are present in a patient without anti-MAG antibodies:

1. Median time to peak of the neuropathy is within 1 year.

2. Clinical course is relapsing and remitting or monophasic.

3. Cranial nerves are involved.

4. Neuropathy is asymmetric.

5. Motor symptoms and signs predominate.

6. History of preceding infection.

7. Presence of abnormal median sensory nerve action potential in combination with normal sural sensory nerve action potential.

Adapted from Notermans NC, Franssen H, Eurelings M, Van der Graaf Y, Wokke JH. Diagnostic criteria for demyelinating polyneuropathy associated with monoclonal gammopathy. Muscle Nerve 2000;23:73-79, with permission of John Wiley and Sons, Inc.

IBM is a disease of adults, most commonly over age 50. It affects men more than it does women. In contrast to PM/DM, the weakness may be asymmetric. The pattern of weakness, with prominent early involvement of quadriceps, finger and wrist flexors, and ankle dorsiflexors (see Table 1), contrasts with proximal greater than distal weakness in PM/DM, and is useful in raising clinical suspicion. The weakness is usually slowly progressive, and many patients are not diagnosed for years after onset.

The nature of the inclusion bodies, and the finding of P-amyloid in muscle fibers has led to theories that IBM may be a degenerative disorder of muscle (with homologies to Alzheimer's disease) or possibly of viral origin.

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