It has been recently recognized that increased titers of serum anti-GM
1 antibodies may be associated with motoneurone diseases or with multi
ple motor neuropathy with or without conduction block and also with ch
ronic sensorimotor neuropathy and Guillain-Barre syndrome. Santoro et
al. were the first to note that anti-GM1 antibodies were able to bind
to the nodes of Ranvier of the sural nerve of a patient with clinical
signs and symptoms mostly resembling amyotrophic lateral sclerosis who
also showed, in nerve conduction studies, multifocal motor nerve fibe
rs conduction block and serum IGM anti-GM1 antibodies. The two patient
s presented in this report had asymetrical motor neurone disease with
signs and symptoms of lower motoneurone involvement, and other signs,
in the first patient, which suggested the existence of upper motoneuro
ne damage. Besides, the second patient also had clinical sensory impai
rment in the lower limbs. Electrophysiologically, none of them had ner
ve conduction block but both showed inexcitable median and sural nerve
sensory fibers. Both had high titers of anti-GM1. A sural biopsy of b
oth patients showed immunoglobulins into the sensory fibers. However,
we do not know whether the anti-GM1 antibodies bind to a cross-reactiv
e glycolipid other than the GM1 itself. In any case, it seems that the
presence of anti-GM1 antibodies might be a marker signalling a potent
ially treatable immune disorder which may have signs of lower and uppe
r motor neurone disease and, also, clinical and electrophysiological e
vidences of peripheral sensory involvement.