Serum IgM anti‐GM1 ganglioside antibodies in lower motor neuron syndromes

Lower motor neuron syndromes (LMNS) are heterogenous conditions, which include patients with progressive lower motor neuron disease (LMND) and cases with the clinical phenotype of motor neuropathy (MN). The aim of this study was to estimate the IgM anti‐GM1 ganglioside antibodies titer and the ratio of the light chains in order to define the presence of autoimmunity process in particular cases with LMNS. Twenty‐eight patients were diagnosed with LMND and 15 patients were diagnosed with MN (10 patients with multifocal motor neuropathy with conduction block, five patients with MN without conduction block). Total of 103 patients with classical amyotrophic lateral sclerosis (ALS) and 50 healthy, age‐matched persons were also tested. The IgM anti‐GM1 ganglioside titer and the ratio of lambda/kappa light chains in serum were determined using the ELISA technique. High titer of IgM anti‐GM1 antibodies were detected in serum of 46% LMND patients, 80% of MN patients, and 18% of the classical ALS cases. An elevated ratio of lambda/kappa light chains appeared in 18% of LMND patients, and in 67% of the MN cases. The lambda/kappa light chains ratio was normal in all ALS patients. The presence of elevated titer of IgM anti‐GM1 ganglioside antibodies and the changed ratio of the light chains supports the presence of autoimmune process in LMNS and may provide clues for their management.