Mixed IgG and IgM anti-GM1 ganglioside antibody positive multifocal motor neuropathy with severe secondary axonal loss in a Filipino female

Approximately 40% of patients with multifocal motor neuropathy had anti-GM1 IgM antibodies, while only 1 out of 88 patients had anti-GM1 IgG antibodies. Unlike its predominantly demyelinating IgM counterpart, the anti-GM1 IgG antibody is often seen in the axonal variant of Guillain Barre syndrome. As it affects axons, it is also associated with worse prognosis. We report here a 58-year-old woman who was admitted for 3 months history of progressive asymmetric weakness, initially involving the right-hand extensors, eventually affecting the contralateral side and the lower extremities. The electrodiagnostic examination revealed multifocal pure motor demyelinating neuropathy with severe axonal loss. On nerve ultrasound, the axons were small in non-compressive areas. The extremely elevated anti-GM1 IgM titer (1:51,200, nv<1:800) was consistent with the diagnosis of MMN. Her anti-GM1 IgG antibodies (1: 12,800, nv<1:800) was also elevated. In conclusion, the presence of concomitant anti-GM IgG and anti-GM1 IgM may lead to an MMN with more severe axonal loss.