Polyclonal IgM anti‐GM₁ ganglioside antibody in patients with motor neuron disease and variants

Recent studies reported the presence of anti‐ganglioside antibodies in occasional patients with motor neuron disease. We found polyclonal serum IgM anti‐GM₁ antibodies by an anti‐GM₁ enzyme‐linked immunosorbent assay (ELISA) in 9 (19%) of 48 patients with motor neuron disease. A comparable frequency of IgM anti‐GM₁ antibodies was found in 4 (10%) of 40 sera from patients with other neurological disease. Three (17%) of 18 sera from the patients with motor neuron disease and 2 (17%) of 12 sera from patients with other neurological diseases had anti‐GM₁ immunostaining as shown by thin layer chromatography immunoblot. One patient with a lower motor neuron variant of motor neuron disease or motor axonopathy without multifocal conduction block had a markedly elevated polyclonal IgM anti‐GM₁ ELISA titer (> 1:64,000) with prominent immunostaining of GM₁, moderate immunostaining of GM₂, and weak and inconsistent immunostaining of GD_1b by thin layer chromatography immunoblot. Treatment with prednisone resulted in clinical improvement despite increasing anti‐GM₁ antibody titers. These data indicate that patients with motor neuron disease have measurable levels of anti‐ganglioside antibodies as frequently as patients with other neurological diseases. This contrasts with a small subgroup of patients with a lower motor neuron variant of motor neuron disease or motor axonopathy who have markedly elevated levels of serum anti‐ganglioside antibodies and a clinical syndrome that is treatable with immunosuppression.