Lower motor neuron syndrome associated with IgG anti-GM1 antibodies revisited

• The patients had neither upper motor neuron signs nor multifocal conduction block.
• Three patients had IgG anti-GM1 antibodies, but no IgM anti-GM1 antibodies.
• IgG anti-GM1 antibodies also should be tested in lower motor neuron syndrome.

A patient, who developed an amyotrophic lateral sclerosis-like disorder subsequent to ganglioside treatment, had IgM antibodies to GM2 as well as to minor gangliosides X1 and X2 containing GM2 epitope. These gangliosides as well as GM1 were tested in 655 sera obtained from patients who were suspected of having amyotrophic lateral sclerosis or motor neuron disease to find a treatable condition. Three patients had high titers of IgG anti-GM1 antibodies, but no IgM anti-GM1 antibodies. One of the patients also had IgG anti-X2 antibodies. The patients, being diagnosed with having lower motor neuron syndrome, had neither upper motor neuron signs nor multifocal conduction block. Both IgM and IgG anti-GM1 antibodies should be tested in patients who have lower motor neuron syndrome.