Serum IgM monoclonal autoantibody binding to the 301 to 314 amino acid epitope of beta-tubulin: clinical association with slowly progressive demyelinating polyneuropathy.

We identified five patients with IgM monoclonal autoantibodies that bound to human brain tubulin. In a companion study, we found that IgM in these sera selectively recognized one of three epitopes on tubulin. IgM from three patients bound selectively to a small epitope on human beta-tubulin comprising amino acids 301 to 314. The other two sera recognized tubulin amino acids 215 to 235 and 315 to 336. In this study, we compared the clinical syndromes in these patients with the tubulin epitope recognized by their serum IgM. The three patients with IgM binding to tubulin amino acids 301 to 314 all had chronic inflammatory demyelinating polyneuropathy (CIDP) syndromes with slowly progressive weakness, hyporeflexia, and electrophysiologic studies consistent with demyelination. Two of these patients had significant asymmetry to their weakness. The two other patients had diagnoses of polyradiculopathy and amyotrophic lateral sclerosis with no evidence of peripheral nerve demyelination. We conclude that IgM monoclonal anti-tubulin antibodies have some association with demyelinating polyneuropathy syndromes, but may occur in patients with other clinical syndromes as well. A stronger association with demyelinating polyneuropathies may occur if the anti-tubulin antibodies recognize the 301 to 314 amino acid epitope on tubulin. This tubulin epitope, or a similar one on another molecule, could play an important antigenic role in the development of demyelinating polyneuropathies with features of CIDP.