[A case of distal lower motor neuron syndrome associated with IgM anti-GM1 antibodies]

A 34-year-old man had noted progressive weakness in his right hand. On admission at age 39, cranial nerves were not involved. Fasciculations were observed in his upper limb girdles. Neurological examination revealed severe wasting and weakness of arms and the right hand, whereas mild in the left hand. The deep tendon reflexes were absent in the upper extremities, but normal in the lower extremities. No sensory disturbances were observed. Motor and sensory nerve conduction velocities were normal, and multifocal conduction block was not observed. EMG showed neuropathic changes in all 4 limbs and sternocleidomastoideus muscles. Serum immunoelectrophoresis failed to detect an M protein. High-performance thin-layer chromatography with immunostaining revealed that his serum IgM reacted with GM1, but not reacted with GM2, GD1a, GD1b, and asialo-GM1.