Lower motor neuron disease in a patient with autoantibodies against Gal(beta 1-3)GalNAc in gangliosides GM1 and GD1b: improvement following immunotherapy.

We followed a patient with a lower motor neuron form of motor neuron disease whose neurologic disorder improved following immunotherapy. The patient did not have an M protein but did have IgM antibodies to ganglioside GM1 detectable at serum titers of 1:2,000 by ELISA. These antibodies were found only in the IgM fraction with lambda light chains and immunoreacted with GD1b and Gal (beta 1-3) GalNAc.