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. © 1994 John Wiley & Sons, Inc.