Treatable gait disorder and polyneuropathy associated with high titer serum IgM binding to antigens that copurify with myelin‐associated glycoprotein

We studied clinical and electrodiagnostic features of 9 patients with very high titers (> 1:10,000) of serum IgM binding to a CNS myelin antigen (CMA) preparation that copurified with myelin-associated glycoprotein (MAG). We found that 8 of the 9 patients had a combined syndrome of gait ataxia and polyneuropathy (GAPN) with late-age onset (mean = 70 years of age). In the 8 GAPN patients progressive difficulty with ambulation led to significant functional disability and frequent falling. Examination showed a wide-based unsteady gait, especially when standing still or turning. There was mild-to-moderate distal sensory loss with involvement of joint position sense only in the toes. Motor changes, when present, were mild and mainly involved distal leg musculature. Treatment of 5 GAPN patients resulted in clear improvement of 2 after intravenous human immunoglobulin and of 3 others after other immunodulating agents. Immune-mediated GAPN syndromes with high titers of serum IgM binding to CMA appear to be treatable causes of gait disorders in older patients.