CD40LG and amyotrophic lateral sclerosis: Unlike ALS, which is believed to be caused by a combination of genetic and environmental factors, MMN clearly has an autoimmune etiology; it is associated with elevated anti-GM1 IgM levels in ~50% of patients and responds to immunomodulatory treatment.21,24–26 The pathophysiology of MMN and CB has been covered elsewhere and will not be reviewed here.24