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SERUM IgM BINDING TO MYELIN-ASSOCIATED GLYCOPROTEIN (MAG)
  IN SENSORY-MOTOR NEUROPATHIES

Indications for measurement
Interpretations of positive results
Laboratory standards
Patterns with specificity for
  demyelinating neuropathies

Therapy: Guidelines
Anti-MAG antibodies: Summary of indications

MAG staining
on Western blot
Indications
Adult onset neuropathy:
  Distal; Symmetric;
  Sensory > Motor
Likelihood of positive test:
  Age > 50
  Gait disorder
  Tremor
  Disability 2° sensory
    or motor loss
  Demyelination
    Usually with
      Distal latency
      No conduction block
  Serum IgM M-protein: 85%
Treatment follow-up
  Document sufficient cytoxan
  Best prognosis:
    Anti-MAG titers by > 60%
    Usually with cytoxan Rx
+ Results
ELISA
  IgM vs MAG > 1,500
  Low IgM vs Histone H3
Western blot confirmation
Clinical correlation: Titer > 6,000
  Demyelinating neuropathy
  90% specificity; 95% sensitivity

Lab standards
Document 90% clinical specificity

Interpretation
Diagnosis
  Dx of immune neuropathy
    Distinguish from CIDP
Prognosis: Slow progression
Treatment
  Cytoxan may be useful
  Prednisone & HIG not useful
Follow-up
  Anti-MAG titer → ? Relapse


I. Clinical Indications for Measurement of anti-MAG antibodies


II. Results with Specificity and Sensitivity for Sensory-Motor Neuropathies


III. Testing Laboratory Standards for anti-MAG Antibodies.


IV. Interpretations of Confirmed Positive anti-MAG Results


V. Guidelines during Cyclophosphamide Therapy.


References
1. Neurology 1994;44:1131-1137

o Demyelinating Neuropathies
Motor Syndromes
Anti-Sulfatide Antibodies
Differential Diagnosis Index
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11/27/2000